An overview of ventilation and indoor air quality in selected wards of the Children's Medical Center

An overview of ventilation and indoor air quality in selected wards of the Children's Medical Center | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article An overview of ventilation and indoor air quality in selected wards of the Children's Medical Center Nazanin Dastjerdi, Mohammad Sadegh Hassanvand, Ali Salimifard, and 3 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7810595/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract In this study, number and concentrations of PM 2.5 , PM 10 , and PM 1 in indoor and outdoor air, temperature, humidity, and CO 2 concentration, and air exchange per hour were examind in selected wards of the Children's Medical Center in Tehran city. To measure number and concentrations of indoor and outdoor particles and air velocity, the PLANTOWER PMS 5003 sensor and KIMO VT 115 (Hotwire thermo-anemometer) was used, respectively. Furthermore To measure temperature, humidity, and carbon dioxide concentration, the Testo 440 device was used. The average air exchange rate per hour in selected wards of the Children's Medical Center during the warm season (April to August) and the cold season (November to December) in 2024 was 24 and 12 times per hour, respectively. The average concentration of PM 2.5 and PM 10 in the cold season (November to December) and the warm season (April to August) at the Children's Medical Center was 32 µg/m³ and 22 µg/m³ and 39 µg/m³ and 28 µg/m³, respectively. The average CO₂ concentration in the Children's Medical Center during the warm season was 270 ppm, which is lower compared to the cold season (390 ppm). Installing and upgrading mechanical ventilation systems using HEPA filters in all wards, especially sensitive areas like NICU, CICU, and operating rooms, can significantly impact the air quality within the wards. Earth and environmental sciences/Environmental sciences Health sciences/Health care Indoor air quality Hospital ACH Ventilation PM Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11 Figure 12 Figure 13 Figure 14 Highlights Air exchange rate per hour was significantly lower in the cold season. CO₂ concentration was higher during the cold season (390 ppm vs. 270 ppm). Average indoor temperature and humidity were slightly higher in the warm season. Microbial pollution index increased during the warm season (21 vs. 17 CFU/plate/h). PM, PM, and PM concentrations were higher in the cold season. 1. Introduction In European countries, people currently spend more than 70 percent of their time indoors 1 . Additionally, it is expected that this percentage will increase with the aging population and remote work. Good indoor air quality is a crucial aspect of a healthy environment and is influenced by several factors, including the ventilation system, the physical features of the home, its location, cooking appliances, lighting and heating, the style of furniture, cleaning supplies, and the habits of the inhabitants, such as smoking. 1 . Residing in a residence with inadequate indoor air quality can lead to several harmful health consequences, such as allergies, respiratory issues, a compromised immune system, irritation of the skin, eyes, nose, and throat, and cancer 1 . In the past few decades, significant modifications have occurred in how buildings are designed and operated. In response to rising fuel costs and the push for greater energy efficiency, modern homes are now constructed with improved insulation. As a result, air exchange rates have decreased—from approximately 1 air change per hour in older buildings to just 0.2–0.3 air changes per hour in many modern homes 2 . While these advancements reduce energy consumption, they also contribute to a significant increase in the concentration of indoor air pollutants. This is particularly alarming because individuals typically stay inside for over 80–90% of their time. Inside spaces can have higher pollution levels compared to the outdoors because of different sources of pollution present indoors 3 . Children who have not yet started school spend more than 85% of their time indoors 4 . On the other hand, pregnant women also spend most of their time indoors, which leads to fetal exposure to indoor air 4 .Young children are more vulnerable to environmental stressors due to their higher metabolic rate, greater air intake per unit of body weight, and the ongoing development of their respiratory systems 5 . Asthma and allergies are among the most common childhood diseases globally, posing a major health concern due to their high economic burden and negative impact on quality of life 6 . Given the importance of indoor air quality and its effects on health, assessing indoor air quality is a vital issue for protecting the health of the general public and should be prioritized in sensitive environments such as hospitals 7 . Studies have shown that 80–90% of hospital infections are transmitted through direct contact, with 10–20% of them are airborne 8 . It has been reported that 14 to 17 percent of all hospital infections are associated with poor air quality 9 . Pollutants such as PM 2.5 (Particulate matter with aerodynamic diameter less than 2.5 micrometers(, VOCs) Volatile organic compounds(, and CO₂)Carbon dioxide( are more common indoorair pollutants, and these pollutants are more closely associated with indoor activities 10 . Particles, including fine particles (PM 2.5 ), are released indoors due to people's walking and outdoor sources 11 . Bioaerosols, a class of airborne pollutants, are often linked to biological compounds. This definition encompasses mycotoxins, peptidoglycans, viruses, high molecular weight allergens, pollen, and any other harmful or harmless bacteria and fungi, whether they are alive or dead 12 . Bioaerosols are able to travel great distances via the wind because of their tiny size and light weight, which might result in both acute and chronic illnesses in people, plants, and animals. The majority of bioaerosols are either produced by human activities or originate naturally 13 . Contaminants can enter interior spaces through ventilation systems when outdoor air pollution rises, having a big impact on indoor air quality. The design and operation of these systems are essential to maintaining healthy indoor environments 14 . The term ventilation refers to the process by which indoor air pollutants are diluted and removed, resulting in clean, breathable air 15 . There are three main types of ventilation systems used in hospitals: natural, mechanical, and combination 15 . Natural ventilation makes use of environmental forces, such as wind and temperature differences between indoor and outdoor air, to move air through openings such as windows and doors 15 . Mechanical ventilation employs fans to supply or exhaust air and can be set up in windows, walls, or duct systems 15 . Combined ventilation combines both natural and mechanical techniques to maximize airflow. This hybrid strategy has a number of benefits, such its ability to adapt to different climates, its energy efficiency, and its system flexibility 16 . The air exchange rate is an important factor for evaluating the efficiency of the ventilation system 17 . The ventilation rate in healthcare facilities is expressed in terms of air change per hour (ACH) and indicates how quickly the air inside the building is replaced with outside air (or processed air). The air change rate (ACH) is defined as the airflow inside the room divided by the volume of that space 17 . For example, if the amount of incoming and outgoing air in one hour equals the total volume of the space, it is said that one air change per hour has occurred in that space 18 . The healthcare facility is considered a critical area. Compared to other public places, the air quality within its various wards is more important since workers, particularly patients, are exposed to chemical and biological pollutants due to their weakened immune systems. Rezaei and colleagues 19 conducted a study to determine the density of airborne bacteria at the Children's Medical Center. In this study, only the infectious, pediatric surgery, blood, and oncology wards were examined. They only examined the microbial quality of the air inside the hospital. Dehghani and colleagues 20 examined the concentration of suspended particles in outdoor and indoor air and determined the correlation between them at Hafiz Hospital in Shiraz. Previous studies have only examined one of the parameters related to indoor air quality. Additionally, previous studies have not examined the type of ventilation system, the measurement of air changes per hour, and their impact on indoor air quality. Because there is little information about the quantity and quality of pollutants present in the indoor air of the children's medical center, and given the importance of examining the ventilation status in the hospital, particularly in areas such as the isolation room, operating room, and so on, conducting this study seems necessary. The aim of this study is to examine the indoor air quality and ventilation status of the hospital wards. In this study, we examine bioaerosols, PM 10 , PM 2.5 , and PM 1 concentration, as well as their quantity in the air, air exchange rate per hour and the CO 2 concentration in the air. 2. Materials and methods 2.1. Study area and schedule The construction of the Children's Medical Center was proposed in 1958 and opened in 1967. Initially, the hospital operated with departments for infectious diseases, nephrology, hematology, endocrinology, surgery, emergency, and specialized clinics. Gradually, departments for cardiology, neonatology, rheumatology, neurology, and others were added to this complex. Today, the Children's Medical Center operates as a reference hospital for children with over 350 active beds. This hospital is located in the Imam Khomeini Hospital Complex. The Imam Khomeini Hospital Complex is situated in the southwest of District 6 of Tehran city, Iran, at coordinates 35°42'21" N and 51°22'57" W (Fig. 1 ). The surrounding areas of the Imam Khomeini Hospital Complex are mostly residential. The entrance to this hospital is located on Dr. Gharib Street.. The first sampling phase began on May 6, 2024. The second phase of sampling began on November 1, 2024. In this study, the Testo 440 device was used to determine the concentration of carbon dioxide gas in ppm, temperature in o C, and humidity in percentage 21 . In this study, the first sampling phase (from May to August) and the second sampling phase (from November to December) will be referred to as the warm and cold seasons for convenience. 2.2. Data collection form To conduct this study, the necessary arrangements were first made with the Children's Medical Center located in the Imam Khomeini Hospital Complex. A data collection form was prepared for each sampling point. This data collection form, designed to assess the indoor air quality at the Children's Medical Center, records the sampling date, sampling location, sampling time, carbon dioxide concentration, temperature, humidity, area of the sampling location, height of the sampling location, type of ventilation system used, window area, Window opening area, number of people present in the room, air flow rate due to natural ventilation if present, air flow rate due to mechanical ventilation if present, area of the air intake vent (in mechanical ventilation, these vents are usually installed on walls or ceilings, and in natural ventilation, this area is the same as the window area), and the shape of the air intake vent. 2.3. Selected wards The selected wards in this research include the endocrinology and nephrology department, hemodialysis, and infectious diseases department located in building number one; the general and cardiac operating rooms, emergency room, NICU, and heart and lung department located in building number two; and the bone marrow transplant and immunology and rheumatology department located in building number three. In selecting the sampling locations, efforts were made to choose wards from all three buildings of the Children's Medical Center based on their importance and high traffic. Additionally, the type of ventilation system used in these wards and whether the building is old or new were considered. In each ward, isolation rooms, if available, and then the busiest and most frequented inpatient rooms were selected for sampling. Figure 2 shows the map of selected wards for sampling at the Children's Medical Center. Table 1 Characteristics of selected wards for sampling wards The floor Building Number of people Type of ventilation system Date of sampling Heart and lung ward Fourth 2 8 Natural and mechanical 16 June 2024, 26 November 2024 Emergency Room basement 2 80 Natural and mechanical 12 May 2024, 3 November 2024 Operating Room Second 2 7 mechanical 22 June 2024, 4 December 2024 Newborns intensive Care Unit Fourth 2 11 Natural and mechanical 20 May 2024, 28 October 2024 bone marrow transplant ward First 3 3 mechanical 30 June 2024, 23 December 2024 immunology and rheumatology ward Third 3 7 Natural 11 June 2024, 16 November 2024 endocrinology and nephrology ward Second 1 6 Natural 22 October 2024, 6 May 2024 infectious diseases ward First 1 6 Natural and mechanical 16 June 2024, 20 November 2024 hemodialysis Second 1 12 Natural 22 October 2024, 6 May 2024 2.4. Air Quality Measurment For this study, the equipment was taken to the Children's Medical Center every 6 days, and each ward was examined on the respective date. 2.4.1. ACH To calculate the air changes per hour, the length, width, and height of the room or sampling location must be measured in meters. To calculate the flow rate of air entering the space through a window or air handling unit, the area of the window or air inlet to the room must also be determined based on its geometric shape by measuring its length and width or calculating the diameter or radius of a circle. After calculating the dimensions of the room and the air inlet to determine the flow rate entering or exiting the room, it is necessary to measure the air velocity in m/s. For this purpose, we used the VT 115 KIMO Hotwire thermo-anemometer, which measures air velocity in m/s 22 . To increase the accuracy of measuring air flow speed, we performed this operation in the corners, at the edges of the window at every 10 cm interval, and at the center of the window at 10 cm intervals. Additionally, to measure the airflow velocity exiting the vents, we also took measurements at the center and edges. Then we calculate the average of the measured values for each window or air inlet. After calculating the air flow velocity in meters per second, we use the following formula to calculate the inlet or outlet flow rate (Eq. 1). Q(m³/s) = V(m/s) × Area (m²) (Eq. 1) After calculating the flow rate, we can determine the air change per hour by calculating the volume of the room or space in equation (Eq. 2). Room volume (m³) = length (m) × width (m) × height (m) (Eq. 2) Then, according to the following formula (Eq. 3), we calculate ACH 15 , 23 : \(\:ACH=\frac{Q\left(\frac{{m}^{3}}{\text{s}}\right)}{\:\text{R}\text{o}\text{o}\text{m}\:\text{v}\text{o}\text{l}\text{u}\text{m}\text{e}\left({m}^{3}\right)\:\:\:}\) (Eq. 3) 2.4.2. Temp, CO 2 , Humidity To measure temperature, relative humidity, and CO₂ concentration, the Testo 440 device was used. The Testo 440 device can measure various environmental parameters depending on the type of probe used 21 . 2.4.3. PM measurement In this study, the PLANTOWER PMS 5003 device (Fig. 3 ) was used to measure the concentration and number of particles 24 . This device is capable of reporting the PM 10 , PM 2.5 , and PM 1 concentration in micrograms per cubic meter. It also reports the number of particles smaller than 0.5, 1, 2.5, 5, and 10 micrometers in terms of number per liter 25 . The principle of laser scattering is applied in these sensors. This means they shine a laser on particles in the air, then gather the scattered light to a certain degree, eventually creating a graph that shows how the intensity of scattered light changes over time. Finally, the equivalent diameter of the particles and the number of particles with different diameters per unit volume can be calculated based on MIE theory (Mie theory, commonly referred to as Lorenz-Mie theory, is a mathematical approach used to explain how electromagnetic waves scatter when they encounter spherical particles.) by a microprocessor 25 . The manufacturer determines the particle size using an unidentified algorithm. The PMS5003's fan forces air through it at 0.1 L m-1, and its laser runs at 680 nm 24 . These sensors were placed at a height of 100–150 centimeters from the ground during sampling. To prevent underestimating the concentration of particles, these sensors were not placed in front of air vents, windows, or air conditioning ducts. 2.4.4. Bioaerosol measurement In this study, we also used TSA culture medium. To prepare the desired culture medium, we followed the instructions mentioned on the container holding the culture medium. To prepare 1000 milliliters of TSA culture medium, it is necessary to dissolve 40 grams of it in 1000 milliliters of distilled water. The culture medium used in this study was powdered. According to the manufacturer's instructions, it is necessary to heat the culture medium in distilled water for one minute after it has dissolved. This step was performed using a heater. After completing this stage, we transfer the culture medium into screw-cap bottles. We place the bottle inside the autoclave and set it at a temperature of 121 o C and a pressure of 15 psi for 15 minutes. After 15 minutes, the culture medium has been sterilized. For passive sampling in this method, we used a 9-centimeter diameter plate. After the temperature of the prepared culture medium decreased, we disinfected the work surface with 70% alcohol. In this study, all steps of distributing the culture medium were performed under the hood. After evenly spreading the culture medium in the plates, we wait for the agar to solidify. Then, we placed the lid on the culture medium and stored it upside down in a sterile refrigerator until use. After preparing the plates containing the desired culture medium under sterile conditions, we randomly selected a few of them and placed them in the incubator at a temperature of 37 o C for 24 hours. The plates were transferred to the sampling site under sterile conditions. After the sampling was completed, the culture media used for sampling were transferred to the laboratory in a cooler with ice at a temperature between 0 and 4 o C. The plates were immediately placed upside down in an incubator at 37 o C, and after 24 and 48 hours, the colonies formed on the culture medium were counted and examined using a colony counter. 2.5. Statistical analysis In this study, we reported only one value for the number of counted colonies, the concentration of benzene, toluene, ethylbenzene, and xylene. However, since the sensors used for measuring concentration and particle count provide us with 5 data points per minute, we used the mean, maximum, minimum, and standard deviation indices to better report the obtained results. For air change per hour, we also calculated the mean, minimum, and maximum air changes per hour. Additionally, to examine the correlation between concentration, particle count, and the number of colonies counted in the hospital air and outdoor air, we first need to check the normality of the data in question. To check the normality of the data, we used the Shapiro-Wilk test. This test checks whether a dataset follows a normal distribution or not. After conducting this test, it was determined that the obtained data do not follow a normal distribution. As a result, Spearman correlation, which does not require a linear relationship or normal data distribution, was used to examine the correlation. To calculate the Spearman correlation coefficient and also to perform the Shapiro-Wilk test and other statistical analyses, we used R software version 4.2.1 and Microsoft Excel 2021. 3. Results and Discussion In order to enhance the reporting of the findings, we organized the chosen wards according to their utilization within the hospital. During the warm season, the classification according to utilization comprises the emergency department, patient admission rooms, critical care units, sterile transplant facilities, surgical suites, nursing stations, diagnostic laboratories, and hemodialysis units. During the winter season, the classification according to utilization encompasses the emergency department, patient admission rooms, critical care unit, sterile transplant facilities, surgical suite, and hemodialysis units. According to Fig. 1 ( a&b), the highest average PM 1 concentration is observed in the emergency ward (18 µg/m³) and inpatient rooms (26 µg/m³) during the warm and cold seasons, respectively.In the warm season, after the emergency ward, the highest PM 1 concentration is in the inpatient rooms (12 µg/m³), which could be due to the density of people, poor ventilation and the opening and closing of doors and windows.In the cold season, after the inpatient rooms, the emergency ward (25 µg/m³) has the highest PM 1 concentration. Additionally, the lowest average concentration of PM 1 in both the warm and cold seasons was observed in the clean rooms of the transplant unit (0 µg/m³). The reason for the decrease in PM 1 concentration in the clean rooms of the transplant ward is the presence of a high-efficiency HEPA filter under the air intake vent to the ward. Additionally, the clean rooms had positive pressure, and the airflow direction in these spaces was from the interior of the ward toward the hallways and other areas.The distribution of data in the emergency room and inpatient room is broader, indicating high variance in particle concentration. This issue could indicate fluctuations in ventilation performance or high population density. The average PM 1 concentration in the winter season in the emergency ward and inpatient rooms is higher than the average PM 1 concentration in the summer season in the same areas.The reason for the increase in PM 1 concentration in the cold season may be related to the increase in the concentration of suspended particles, including PM 1 , in the outdoor air. Furthermore, the emergency room (30 µg/m³) has the highest average PM 2.5 concentration during the warm season, while the inpatient rooms (44 µg/m³) have the highest average PM 2.5 concentration during the cold season (Fig. 1 (c & d)). Due to the large number of patients and regular disinfection in the emergency room, the PM 2.5 concentration is probably higher than in other areas. The emergency room (39 µg/m³) has the highest average PM 10 concentration during the warm season, while the inpatient rooms (53 µg/m³) have the highest average concentration of PM 10 during the cold season (Fig. 1 (e & f)). In the pediatric surgery, operating room, and emergency room of the hospital, Shahid Uz Zaman and colleagues reported the average PM 1 , PM 2.5 , and PM 10 concentrations during the warm season to be 48.25 µg/m³, 64.00 µg/m³, and 73.75 µg/m³, respectively; 44.50 µg/m³, 59.25 µg/m³, and 68.25 µg/m³; and 29.17 µg/m³, 39.00 µg/m³, and 45.17 µg/m³ 26 . Shahid Uz Zaman and colleagues found that the average concentrations of PM 1 , PM 2.5 , and PM 10 were higher during the warm season than in the current investigation. The PM 2.5 concentration in the indoor environment of each hospital is positively correlated with the PM 2.5 concentration in the outdoor environment. The concentration may also be influenced by factors like the number of people present, the ambient temperature, the size of the room, and the number of windows and doors. Furthermore, the concentration of suspended particles in both indoor and outdoor settings may depend on wind speed 27 . Hand washing at sinks, utilizing medical sprays, carrying out nebulizations, making beds, and cleaning activities are examples of actions that can directly impact the concentration of airborne particles inside hospitals 28 . The average PM 2.5 concentration in the hospitals they studied was reported as 52.28 µg/m 3 and 222.353 µg/m 3 in the fall and winter seasons, respectively 26 . The average PM 2.5 concentration in the cold and warm seasons at the Children's Medical Center was 32 µg/m³ and 22 µg/m³, respectively, which was lower compared to the study by Shahid Uz Zaman and colleagues. In a study, the median PM 2.5 concentration in the warm season was higher than in the cold season 11 . The results of this study differ from the current study in the children's hospital. During the warm season, work areas in the hospital, including the clinic, clinic waiting area, reception, lobby, staff office, hallway, meeting room, and ophthalmology patient room, had PM 2.5 concentration levels higher than the standard recommended by WHO (25 µg/m 3 ). The elevated levels of PM2. 5 and PM10 during the warm season can be linked to the presence of regional dust storms, as well as the increased population density and human activities in these locations 10 . Derikvand and colleagues reported an average PM 2.5 concentration of 20–233 µg/m³ in public places in Tehran. The highest average PM 2.5 concentration (233µg/m³) was found in hookah cafes. The lowest average PM 2.5 concentration (20 µg/m3) was found in sports clubs. In this study, the average PM 2.5 concentration in the hospital was 21 µg/m³ 29 . The average PM 2.5 concentration in the cold and warm seasons at the Children's Medical Center was 32 µg/m³ and 22 µg/m³, respectively, which was higher compared to the study by Derikvand et al 29 . The number of particles less than 10, 2.5, and 1 micrometer in diameter per liter of indoor air during the warm and cold seasons is represented by the Fig. 2 . In the emergency room and inpatient rooms, respectively, the maximum number of particles less than 10, 2.5, and 1 micrometer per liter of air are found during the warm and cold seasons. Following that, the emergency department and inpatient rooms have the greatest number of particles in the warm and cold seasons that are less than 10, 2.5, and 1 micron in size per liter of air, respectively. In the transplant department's clean rooms, the fewest particles smaller than 10, 2.5, and 1 micron are seen in the warm and cold seasons (Fig. 2 (a, b, c, d, e & d)). In every ward, the average number of particles smaller than 10 micrometers per liter of air is higher in the cold season than in the warm season. The temperature inversion in the cold season, followed by an increase in airborne suspended particles, is the cause of the higher concentration of suspended particles during the cold season as opposed to the warm one. In a study conducted in Malaysia, the number of particles smaller than 10, 5, and 0.5 micrometers per cubic meter of air was measured in 4 operating rooms. The number of particles smaller than 10 micrometers in the 4 operating rooms was reported as 225, 53, 293, and 41 particles per cubic meter of air, respectively 23 . In a study in the city of Qazvin, the number of particles smaller than 2.5 and 0.3 micrometers per cubic meter of air was measured in different sections of a hospital. They reported the highest number of particles smaller than 2.5 and 0.3 micrometers per cubic meter of air in the women's surgery and emergency sections 30 . 3.1. The quantity and concentration of particles in the outdoor air The PM 1 , PM 2.5 , and PM 10 concentration in the ambient air, measured in micrograms per cubic meter, is shown in Fig. 3 . In the warm and cold seasons, the average PM 1 concentration is 12 µg/m 3 and 34 µg/m 3 , respectively. The average PM 2.5 concentrations during the warm and cold seasons are 18 µg/m 3 and 56 µg/m 3 , respectively. The average PM 10 concentration is 20 µg/m 3 during the warm season and 66 µg/m 3 during the cold season. The average PM 1 , PM 2.5 , and PM 10 concentration has been higher during the cold season than during the warm season. The higher concentration of airborne suspended particles in outdoor air during the cold season may be due to the air inversion in the cold season and the increase in the concentration of airborne suspended particles. Shahid Uz Zaman and colleagues reported the average concentrations of PM 1 , PM 2.5 , and PM 10 in outdoor air during the warm and cold seasons in three hospitals as 49.05 µg/m³, 65.47 µg/m³, and 75.47 µg/m³ and 188.80 µg/m³, 248.92 µg/m³, and 288.33 µg/m³, respectively 26 . In comparison to the current study conducted at the children's hospital, Shahid Uz Zaman and colleagues' research conducted across three hospitals in the warm and cold seasons yielded superior results. Figure 4 relates to the number of particles smaller than 10, 2.5, and 1 micrometer per liter of air during the warm and cold seasons in the open air. The average number of particles smaller than 10, 2.5, and 1 micrometer per liter of air during the cold season is higher than in the warm season. 3.2. Air change per hour(ACH) Table 1 displays the minimum, average, and maximum air changes per hour (ACH) for specific areas in the children's hospital, tracked during both warm and cold seasons. The most notable average ACH during the warm season was noted in the Intensive Care Unit (ICU), followed closely by the clean rooms in the transplant ward. Conversely, the emergency department reported the lowest average ACH for this period (Fig. 5 (a)). Table 2 Minimum, average and maximum air changes per hour in selected wards during the warm and cold season in a children's hospital section ACH min ACH ave ACH max Type of ventilation system Warm season Emergency 3 5 9 Natural and mechanical Inpatient rooms 0 18 116 Natural and mechanical Operating rooms 1 9 21 mechanical clean rooms 6 46 121 mechanical Intensive Care Unit 0 51 429 Natural and mechanical Hemodialysis 2 16 46 natural Cold season Emergency 1 4 7 Natural and mechanical Inpatient rooms 0 3 31 Natural and mechanical Operating rooms 0 1 2 mechanical clean rooms 1 22 72 mechanical Intensive Care Unit 5 44 115 Natural and mechanical Hemodialysis 1 5 13 natural During the cold season, the ICU and clean rooms again recorded the highest average ACH, whereas the operating room experienced the lowest (Fig. 5 (b) ) . In general, the average ACH across all selected wards was higher in the warm months than in the cold months. Elements such as the size of the rooms, the number and size of openable windows, and their arrangement played a crucial role in enhancing the ACH. In this research, the choice of utilizing natural ventilation was left up to the patients. With favorable weather from May to August, windows could be fully opened, greatly boosting the ACH during warmer months. Although natural ventilation can significantly improve ACH, it may also lead to the ingress of particles and other outdoor pollutants into the indoor environment. Additionally, an ACH that exceeds 20 times per hour could result in too much airflow disruption and raise ventilation expenses. Reliable sources suggest that an ideal ACH should be around 12 times per hour 18 . As a result, during the warm season, the average ACH in both the emergency ward and operating room fell short of the suggested value. In the cold season, the emergency ward, inpatient rooms, operating room, and hemodialysis unit also had an average ACH that was below the recommended limit. The average air exchange rate per hour in selected wards of the Children's Medical Center during the warm season was 24 times per hour. Additionally, the average air exchange rate per hour in selected wards of the Children's Medical Center during the cold season was 12 times per hour. In comparison to the warm season, the average air exchange rate per hour fell during the cold season. The reason for the decrease in the air exchange rate per hour in the cold season compared to the warm season is the lack of natural and mechanical ventilation in the ward due to the drop in temperature. The recommended air exchange rate per hour for the operating room is 15 times per hour 15 , 31 . The hourly air exchange rate in the operating room during both the cold and warm seasons fell short of the suggested standards. The simultaneous use of natural and mechanical ventilation in hospital wards, although it increases the air exchange rate per hour, will lead to energy waste and increased costs related to cooling and heating systems in each ward. Since only the transplant and operating room wards use return air from the ward for re-ventilation, not using return air will result in a significant waste of energy. Since the air entering the air handling system requires cooling in the summer and heating in the winter, increased use of mechanical ventilation will lead to energy waste 31 . Huiyi Tan and colleagues reported the air exchange rates per hour for operating rooms 1, 2, 3, and 4 as 40, 33, 29, and 32, respectively 23 . The average air changes per hour in the operating room in the present study were 8.8 and 0.7 air changes per hour in the warm and cold seasons, respectively. The average air exchange per hour in the study by Huiyi Tan and colleagues was higher compared to the present study. 3.3. Temperature, humidity, and carbon dioxide concentration Chart 6 shows the concentration of CO2 in various hospital wards during the warm and cold seasons. During the warm season, the highest average concentration is observed in the emergency ward (436 ppm), followed by inpatient rooms (355 ppm), and the lowest in clean transplant rooms (65.8 ppm) (Fig 6 (a)). During the cold season, carbon dioxide average concentration rise in inpatient rooms (490 ppm) and fall to their lowest point in the hemodialysis (67 ppm) (Fig 6 (b)). The low concentration of carbon dioxide in the clean transplant rooms could be attributed to the small number of occupants - only one person is usually present. Furthermore, the presence of opposing windows and a larger air exchange rate per hour in the hemodialysis part contribute to the area's lower CO2 levels. The average CO 2 concentration at the Children's Medical Center during the warm season was 270 ppm. Additionally, the average CO 2 concentration at the Children's Medical Center during the cold season was 390 ppm. The average CO 2 concentration in the children's medical center during the warm season was lower compared to the cold season. The reason for the increase in CO 2 concentration in the cold season is that the average air exchange rate per hour in the cold season has decreased compared to the warm season. The average CO 2 concentration in the winter and summer seasons in the Rennes and Nancy hospitals in France is 498 ppm and 411 ppm and 548 ppm and 479 ppm, respectively 32 . The average CO 2 concentration in the Children's Medical Center during the warm season was 270 ppm, which was lower compared to the Rennes and Nancy hospitals. The average CO 2 concentration in the Children's Medical Center during the cold season was 390 ppm, which was lower compared to the Rennes and Nancy hospitals. Chamseddine A and colleagues 10 found that the hospital clinic area had the highest concentration of carbon dioxide gas throughout both the warm and cold seasons. They also found the lowest concentration of carbon dioxide gas in the pediatric rooms and emergency department during the warm and cold seasons, respectively 10 . The findings of Chamseddine A's study do not correspond to the current study at the Children's Medical Center. The average number of people present in the selected departments during the warm season was 11. During the cold season, the selected sections had an average population of 12 persons. During the cold season, the average number of individuals in each region increased compared to the warm season, potentially contributing to the rise in CO 2 concentrations. Carbon dioxide is a byproduct of human metabolism and is present in large amounts in human exhalation. The average concentration of carbon dioxide in the exhaled air of individuals is around 40,000 ppm. The concentration of carbon dioxide gas is directly related to the ventilation rate in enclosed spaces. In a clinical space with good ventilation, the CO 2 concentration in most areas is less than 400 ppm 33 . The concentration of CO 2 gas should not exceed 1000 ppm, and its average concentration should be less than or equal to 500 ppm 34 . Since the number of people in the emergency ward and inpatient rooms is high, the concentration of carbon dioxide gas in these areas increases. Figure 7 shows the temperature in o C in selected wards during the warm and cold seasons. The highest average temperature in the warm season is observed in the clean rooms of the transplant ward (31 o C). Additionally, the lowest average temperature in the warm season is observed in the hemodialysis ward (24 o C) (Fig. 7 (a)). The highest average temperature in the cold season is observed in the emergency ward (37 o C), and the lowest average temperature in the cold season is observed in the operating room(22 o C) (Fig. 7 (b)). To ensure the thermal comfort of patients in the hospital, maintaining temperature and humidity within specified ranges is important. The recommended values by ASHRAE 170 for temperature and humidity are 21–24 o C and 40–60%, respectively 35 . The average temperature in selected wards of the Children's Medical Center during the warm season has been 27°C. The average temperature in the cold season was 25°C. The average temperature in the cold season has been lower than in the warm season because the second sampling phase was conducted in the fall and winter, when the temperature is lower. Overall, the average temperature in the cold and warm seasons was higher than the standard amount. The average temperature in the summer and winter seasons at the Rennes and Nancy hospitals was reported as 23.8°C and 23 o C, and 24.5 o C and 22 o C, respectively 32 . The average temperature measured in hospitals in France is lower than the average temperature measured at the children's medical center. Figure 8 illustrates the humidity in selected wards during the warm and cold seasons. The highest and lowest average humidity in the warm season was observed in the operating room (40%) and intensive care unit (22%), respectively (Fig. 8 (a)). Also, the highest and lowest average humidity in the cold season was observed in the Inpatient rooms (36%) and hemodialysis unit (18%), respectively (Fig. 8 (b)). The average humidity in the selected sections of the Children's Medical Center during the warm season was 32%. The average humidity in the cold season was 31%. The typical humidity during the warm months is greater than that in the colder months, as the initial sampling took place in the spring and summer seasons. The measured humidity levels in hospitals A, B, C, and D were reported as 56.9–72.6%, 52.6–59.9%, 62.9–77.9%, and 52.9–67.8%, respectively 35 . The average humidity measured at the Children's Medical Center was lower compared to the four hospitals in Malaysia. The average humidity measured in the two hospitals, Rennes and Nancy, in the winter and summer seasons was 35.4% and 24.4% and 44.1% and 55.4%, respectively 32 . The average humidity in the warm season at the Children's Medical Center was lower compared to the two hospitals, Rennes and Nancy. The average humidity in the cold season at the Children's Medical Center was lower than at Rennes Hospital but higher than at Nancy Hospital. 3.4. Bioaerosols Figure 9 relates to the number of colonies counted on each plate after 24 and 48 hours in selected wards of the Children's Medical Center during the warm and cold seasons. The highest number of colonies counted after 24 hours in both the warm and cold seasons is observed in the inpatient rooms (Fig. 9 (a & b)). The number of colonies counted in the inpatient rooms increased in the warm season compared to the cold season. Additionally, the lowest number of colonies counted after 24 hours in both the warm and cold seasons is observed in the clean transplant rooms (Fig. 9 (a & b)). The number of colonies counted after 24 hours in the clean transplant rooms increased in the warm season compared to the cold season. Five classes of the Airborne Microbial Pollution Index (IMA) have been defined: 0–5 very good, 6–25 good, 26–50 moderate, 51–75 poor, and more than 76 very poor. Another ranking has also been proposed for this index, where values of 5, 25, and 50 indicate moderate, high, and very high risk, respectively 36 . The average number of colonies counted in the cold and warm seasons at the Children's Medical Center is in good condition compared to the standards. Mara Di Giulio and colleagues reported the average number of colonies counted per plate during the period from April to June in buildings A, B, and C as 1.1–8.41 CFU/plate/h, 0.5–3.8 CFU/plate/h, and 1.1–20.3 CFU/plate/h, respectively. The average number of colonies counted per plate during the October to December period in buildings A, B, and C were 0–11 CFU/plate/h, 2.1–5.7 CFU/plate/h, and 1.3–17 CFU/plate/h, respectively. All measurements taken pertain to the morning time period 37 . The results of the study by Mara Di Giulio and colleagues showed that the microbial pollution index in the warm season was higher compared to the cold season. Since the temperature and relative humidity are higher in the warm seasons, it can lead to an increase in the air microbial pollution index during these periods. The microorganisms found in indoor air come not only from the activities of the people living there but also from polluted building materials and air from outside 37 . The results of the present study at the Children's Medical Center also showed that the average microbial pollution index in the warm season (21CFU/plate/h) was higher compared to the cold season (17CFU/plate/h), which is consistent with the study by Mara Di Giulio and colleagues. Ersel Sonmez and colleagues reported the number of bacterial colonies counted in the spring and summer before, during, and after the autopsy as 9.1 CFU/plate/h, 51.1 CFU/plate/h, 21.6 CFU/plate/h, 27.4 CFU/plate/h, 60.9 CFU/plate/h, and 19.7 CFU/plate/h, respectively. The results of this study showed that the number of bacterial and fungal colonies in the air of the autopsy room during the autopsy was significantly higher than before and after the autopsy. The temperature and humidity of the autopsy room had a significant impact on the growth of fungal colonies. In the summer, the temperature was higher and the humidity lower, which was associated with reduced fungal growth. The number of people present in the room and the number of autopsies had a direct impact on the number of bacterial colonies 38 . Buildings with a higher number of people have higher levels of suspended particles (PM), bacteria, and fungi. The increase in the number of people in an enclosed space leads to a significant rise in the concentration of bioaerosols (biological particles suspended in the air), with these concentrations reported to be 1.2 to 3.5 times higher than in conditions without people present 39 . In the present study at the Children's Medical Center, during the first and second sampling phases conducted in the warm and cold seasons, respectively, the number of counted colonies in the inpatient rooms increased with a higher number of patients. The results of both studies indicate that temperature and humidity play a significant role in the growth of microbial colonies. In the summer, higher temperatures were associated with increased bacterial growth and decreased fungal growth. In both studies, the number of individuals present in the room and the level of activity (such as the number of hospitalized patients or autopsies) were directly related to the increase in the number of microbial colonies. During the summer season, the chosen areas of the Children's Medical Center had an average air exchange rate of 24 times per hour. Furthermore, during the cold season, the chosen areas of the Children's Medical Center had an average air exchange rate of 12 times per hour. The influx of fresh air into the room during the warm season may have contributed to the increase in the number of colonies counted in the chosen wards, as the air exchange rate per hour has increased in comparison to the cold season and the number of colonies counted in the open air during the warm season is higher than in the cold season. Figure 10 relates to the number of colonies counted on each plate after 24 and 48 hours of incubation in the outdoor air during the warm and cold seasons. The number of colonies counted after 24 hours in the outdoor air during the warm season is higher than in the cold season (Fig. 10 (a & b)). The reason for the increase in the number of colonies in the warm season compared to the cold season is the rise in temperature and humidity during the warm season. 3.5 The correlation between the concentration and the number of particles in the hospital air and the outdoor air After evaluating research similar to the current study at the Children's Medical Center, the majority of the studies employed Pearson correlation to establish the relationship between particle concentration in hospital air and outdoor air 40 , 41 . Pearson correlation applies when the data has a normal distribution. In this study at Children's Medical Center, we used Spearman correlation to assess the non-normality of the acquired data. According to the Fig. 11 , the more we move from lighter shades of purple to darker ones, the correlation increases. In this chart, the correlation between concentration and the number of particles in indoor air and outdoor air has been examined. The correlation between concentration and particle count in indoor air is close to one. The correlation between concentration and particle count in outdoor air is also close to one. The correlation values between the PM 1 , PM 2.5 , and PM 10 concentrations in indoor and outdoor air are 0.61, 0.59, and 0.59, respectively. A higher numerical value of correlation indicates that as the concentration of suspended particles in the outdoor air increases, their concentration in the indoor air also increases. 4. Limitations of the study and potential future perspectives This study does not consider daily, seasonal, and annual variations in pollutants, as well as hourly air exchange, and these measurements were conducted only over a limited time. The study was conducted cross-sectionally, and the long-term impact of air quality improvement measures has not been examined. The relationship between air quality and health outcomes for patients and staff has not been directly measured. In future studies, it is suggested to calculate the air changes per hour in different situations regarding the on and off states of the mechanical ventilation system and the opening or closing of windows. Additionally, more precise methods can be used in future studies, such as measuring the reduction of carbon dioxide concentration over time and then calculating the air changes per hour. 5. Conclusion The present study at the Children's Medical Center examined the impact of various environmental factors, including ventilation systems, temperature, humidity, number of people present, and types of activities, on the indoor air quality of the hospital. The results indicated that the average ACH in the warm season was higher than in the cold season. The increase in the air change rate per hour in the warm season may be related to the greater use of the natural ventilation system. Additionally, the number of colonies counted after 24 hours in the warm season has increased compared to the cold season. Since the temperature and humidity in the warm season are higher than in the cold season, it can lead to increased bacterial growth. The mechanical ventilation system with HEPA filters (in the linkage section) was highly effective in reducing suspended particles. The average PM 2.5 , PM 10 , and PM 1 concentration in the Children's Medical Center during the cold season (November to December) is higher than in the warm season (April to August). In the cold season, outdoor air pollution caused by phenomena such as temperature inversion and combustion activities (like fossil fuels) increases. This pollution may enter indoor air through ventilation systems and contribute to the increase in particle concentration in the indoor environment. Temperature inversion, as well as an increase in particle concentration and quantity, occur often in Tehran throughout the late fall and winter months. The results of this study showed that in places with higher population density, such as the emergency department and inpatient rooms, the concentration of pollutants is higher and the air quality in these areas is not acceptable. Environmental elements and ventilation system performance have a direct impact on the hospital's air quality. Additionally, the correct utilization and efficacy of these systems are compromised due to the fact that the patients in each sector are responsible for adjusting the ventilation system settings. Patients, on the other hand, do not feel comfortable or at peace with the room temperature when ventilation systems are turned on during the cold season, so they turn them off. Using effective ventilation systems and limiting the number of people in the wards can greatly improve air quality and create a safer environment for patients and staff. Declarations Competing interests The authors declare no competing interests. Funding The budget of this project has been provided by Center for Air Pollution Research (CAPR), Institute for Environmental Research (IER), Tehran University of Medical Sciences (Grant number: 1403-3-110-74055 ). Author Contribution N.D., M.S.H., A.S., M.T.M., S.J., and K.N. contributed to the conception and design of the study. N.D. and M.S.H. performed the experiments and collected data. A.S. and M.T.M. conducted data analysis and interpretation. S.J. assisted with methodology and validation. K.N. supervised the project and secured funding. N.D. and M.S.H. wrote the initial manuscript draft. All authors reviewed, edited, and approved the final manuscript. Acknowledgement The authors would like to acknowledge the Children's Medical Center, Tehran University of Medical Sciences for their collaborations. I would like to sincerely thank the managers and all the staff of the Children's Medical Center for their good cooperation. This research was financially supported by Center for Air Pollution Research (CAPR), Institute for Environmental Research (IER), Tehran University of Medical Sciences (Grant number: 1403-3-110-74055). Data Availability The file associated with the retrieved articles for this study is available through the corresponding author for a suitable reason. References Plazas, F. L. & de Tejada, C. S. Natural ventilation to improve indoor air quality (IAQ) in existing homes: The development of health-based and context-specific user guidelines. Energy Build. 314 , 114248 (2024). Jones, A. P. Indoor air quality and health. Atmos. Environ. 33 (28), 4535–4564 (1999). Wang, J. et al. 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07:13:54","extension":"xml","order_by":57,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":140617,"visible":true,"origin":"","legend":"","description":"","filename":"ee49124e3f544bfeaa0c9a1f5af8c7051structuring.xml","url":"https://assets-eu.researchsquare.com/files/rs-7810595/v1/a66df2655d9048c47bdfd386.xml"},{"id":96242918,"identity":"e84faa8c-71bf-4198-9bbb-6c97c8fc09e0","added_by":"auto","created_at":"2025-11-19 07:14:51","extension":"html","order_by":58,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":156761,"visible":true,"origin":"","legend":"","description":"","filename":"earlyproof.html","url":"https://assets-eu.researchsquare.com/files/rs-7810595/v1/66012497c035fa579831721f.html"},{"id":95895523,"identity":"20c8b9a4-43b2-4583-87cf-beee4730d42f","added_by":"auto","created_at":"2025-11-14 07:13:11","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":273473,"visible":true,"origin":"","legend":"\u003cp\u003eLocation of the Children's Medical Center in District 6, Tehran Province\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-7810595/v1/467f397e72dc9f91c8099afc.png"},{"id":95895524,"identity":"9b38b488-7b3b-49dc-82ce-3bed11662492","added_by":"auto","created_at":"2025-11-14 07:13:11","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":162142,"visible":true,"origin":"","legend":"\u003cp\u003eMap of selected wards of the Children's Medical Center for sampling\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-7810595/v1/f367b75bf1071a88c7e85015.png"},{"id":96242954,"identity":"3f4a7fc5-654e-43f9-b6a4-417962ddc001","added_by":"auto","created_at":"2025-11-19 07:15:01","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":268685,"visible":true,"origin":"","legend":"\u003cp\u003ePLANTOWER PMS 5003 device\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-7810595/v1/c167092e894c7825a07d2a47.png"},{"id":96242038,"identity":"c56b60e1-455e-4e24-ab32-73947824faed","added_by":"auto","created_at":"2025-11-19 07:11:53","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":80471,"visible":true,"origin":"","legend":"\u003cp\u003ePM \u003csub\u003e1\u003c/sub\u003e ,PM\u003csub\u003e2.5 \u003c/sub\u003e,PM\u003csub\u003e10\u003c/sub\u003e\u0026nbsp; concentration in selected departments of the Children's in the warm and cold season\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-7810595/v1/a1b9df8cc062e5e6894fda52.png"},{"id":95895530,"identity":"fa4967b5-6d23-456a-8bb0-6a2553ce0dbb","added_by":"auto","created_at":"2025-11-14 07:13:12","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":135473,"visible":true,"origin":"","legend":"\u003cp\u003eParticles less than 10 , 2.5 , 1µm in selected departments of the Children's hospital in the warm and cold season\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-7810595/v1/810a557ce56fd44c9c6d9401.png"},{"id":96243292,"identity":"74976cf2-e01d-41fc-8ed7-8d61588aa022","added_by":"auto","created_at":"2025-11-19 07:15:59","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":33097,"visible":true,"origin":"","legend":"\u003cp\u003ePM\u003csub\u003e1\u003c/sub\u003e ,PM\u003csub\u003e2.5 \u003c/sub\u003e,PM\u003csub\u003e10\u0026nbsp; \u003c/sub\u003econcentration in outdoor air in hot and cold season\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-7810595/v1/898ef2f34d8941bd94c0f983.png"},{"id":96243900,"identity":"8352380c-305e-4510-a5be-b12fccb07e28","added_by":"auto","created_at":"2025-11-19 07:17:16","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":41157,"visible":true,"origin":"","legend":"\u003cp\u003eParticles less than 10, 2.5, 1 µm in outdoor air in hot and cold season\u003c/p\u003e","description":"","filename":"7.png","url":"https://assets-eu.researchsquare.com/files/rs-7810595/v1/d99cb258a0b340429cb6e58d.png"},{"id":95895539,"identity":"0257b9e5-add9-4377-aeca-8e9d98a3de92","added_by":"auto","created_at":"2025-11-14 07:13:12","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":91706,"visible":true,"origin":"","legend":"\u003cp\u003eAir changes per hour in selected wards in a children's hospital during a) warm season and b) cold season\u003c/p\u003e","description":"","filename":"8.png","url":"https://assets-eu.researchsquare.com/files/rs-7810595/v1/861bc9827c98d9402ab8428e.png"},{"id":95895535,"identity":"cd7c9c94-1b21-4f82-8f04-42fbfa10fe46","added_by":"auto","created_at":"2025-11-14 07:13:12","extension":"png","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":47379,"visible":true,"origin":"","legend":"\u003cp\u003eCarbon dioxide concentration in selected departments of the Children's hospital a) in the warm season, b) in the cold season\u003c/p\u003e","description":"","filename":"9.png","url":"https://assets-eu.researchsquare.com/files/rs-7810595/v1/117be2a5ef94a3050523dfe4.png"},{"id":96241982,"identity":"2426b40a-ec98-4596-af42-51df453ccac6","added_by":"auto","created_at":"2025-11-19 07:11:49","extension":"png","order_by":10,"title":"Figure 10","display":"","copyAsset":false,"role":"figure","size":38381,"visible":true,"origin":"","legend":"\u003cp\u003eBox plot of temperature in selected wards of a children's hospital a) in the warm season, b) in the cold season\u003c/p\u003e","description":"","filename":"10.png","url":"https://assets-eu.researchsquare.com/files/rs-7810595/v1/125c92a0e3482dd479591218.png"},{"id":96244133,"identity":"3396e612-b1c0-4bf6-8177-2170be388a95","added_by":"auto","created_at":"2025-11-19 07:17:50","extension":"png","order_by":11,"title":"Figure 11","display":"","copyAsset":false,"role":"figure","size":42156,"visible":true,"origin":"","legend":"\u003cp\u003eBox plot of humidity in selected wards of a children's hospital a) in the warm season, b) in the cold season\u003c/p\u003e","description":"","filename":"11.png","url":"https://assets-eu.researchsquare.com/files/rs-7810595/v1/458f4e058a0b1fb28d3b5be6.png"},{"id":96242071,"identity":"755f9ca8-a9ef-4784-b0e0-a563bcbc2c12","added_by":"auto","created_at":"2025-11-19 07:11:54","extension":"png","order_by":12,"title":"Figure 12","display":"","copyAsset":false,"role":"figure","size":58419,"visible":true,"origin":"","legend":"\u003cp\u003eNumber of colonies counted after 24 and 48 hours of incubation in selected sections a) in the cold season, b) in the warm season\u003c/p\u003e","description":"","filename":"12.png","url":"https://assets-eu.researchsquare.com/files/rs-7810595/v1/e035c2169b054d4f8cd91945.png"},{"id":96242286,"identity":"402b9a31-61a0-49ae-a8fa-6671e5df2320","added_by":"auto","created_at":"2025-11-19 07:12:33","extension":"png","order_by":13,"title":"Figure 13","display":"","copyAsset":false,"role":"figure","size":20032,"visible":true,"origin":"","legend":"\u003cp\u003eNumber of colonies counted after 24 and 48 hours of incubation a) in the warm \u0026nbsp;season, b) in the cold season\u003c/p\u003e","description":"","filename":"13.png","url":"https://assets-eu.researchsquare.com/files/rs-7810595/v1/586fe14cfb8a4641507a79c4.png"},{"id":96242625,"identity":"7cab54c4-ad19-4029-b09f-7b9b0f5d4738","added_by":"auto","created_at":"2025-11-19 07:13:48","extension":"png","order_by":14,"title":"Figure 14","display":"","copyAsset":false,"role":"figure","size":715668,"visible":true,"origin":"","legend":"\u003cp\u003eThe correlation between the concentration and the number of particles in the hospital air and the outdoor air over the entire sampling period.\u003c/p\u003e","description":"","filename":"14.png","url":"https://assets-eu.researchsquare.com/files/rs-7810595/v1/24221a041361a9262eb9987b.png"},{"id":98774801,"identity":"4842094a-a96e-4d2e-a6de-98f45ad08494","added_by":"auto","created_at":"2025-12-22 12:14:34","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":3110615,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7810595/v1/c7dad650-a633-4080-9f44-7b3b6e3c58de.pdf"},{"id":95895522,"identity":"8dc28f1a-7cff-42fe-b098-3ac285cc87f4","added_by":"auto","created_at":"2025-11-14 07:13:11","extension":"png","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":207481,"visible":true,"origin":"","legend":"\u003cp\u003eGraphical abstract\u003c/p\u003e","description":"","filename":"Graphicalabstract.png","url":"https://assets-eu.researchsquare.com/files/rs-7810595/v1/69910a60caa7491416e84ea0.png"}],"financialInterests":"No competing interests reported.","formattedTitle":"An overview of ventilation and indoor air quality in selected wards of the Children's Medical Center","fulltext":[{"header":"Highlights","content":"\u003cp\u003eAir exchange rate per hour was significantly lower in the cold season.\u003c/p\u003e\u003cp\u003eCO₂ concentration was higher during the cold season (390 ppm vs. 270 ppm).\u003c/p\u003e\u003cp\u003eAverage indoor temperature and humidity were slightly higher in the warm season.\u003c/p\u003e\u003cp\u003eMicrobial pollution index increased during the warm season (21 vs. 17 CFU/plate/h).\u003c/p\u003e\u003cp\u003ePM, PM, and PM concentrations were higher in the cold season.\u003c/p\u003e"},{"header":"1. Introduction","content":"\u003cp\u003eIn European countries, people currently spend more than 70 percent of their time indoors \u003csup\u003e\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e. Additionally, it is expected that this percentage will increase with the aging population and remote work. Good indoor air quality is a crucial aspect of a healthy environment and is influenced by several factors, including the ventilation system, the physical features of the home, its location, cooking appliances, lighting and heating, the style of furniture, cleaning supplies, and the habits of the inhabitants, such as smoking. \u003csup\u003e1\u003c/sup\u003e. Residing in a residence with inadequate indoor air quality can lead to several harmful health consequences, such as allergies, respiratory issues, a compromised immune system, irritation of the skin, eyes, nose, and throat, and cancer \u003csup\u003e\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003eIn the past few decades, significant modifications have occurred in how buildings are designed and operated. In response to rising fuel costs and the push for greater energy efficiency, modern homes are now constructed with improved insulation. As a result, air exchange rates have decreased\u0026mdash;from approximately 1 air change per hour in older buildings to just 0.2\u0026ndash;0.3 air changes per hour in many modern homes \u003csup\u003e\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u003c/sup\u003e. While these advancements reduce energy consumption, they also contribute to a significant increase in the concentration of indoor air pollutants. This is particularly alarming because individuals typically stay inside for over 80\u0026ndash;90% of their time. Inside spaces can have higher pollution levels compared to the outdoors because of different sources of pollution present indoors \u003csup\u003e\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003eChildren who have not yet started school spend more than 85% of their time indoors \u003csup\u003e\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e\u003c/sup\u003e. On the other hand, pregnant women also spend most of their time indoors, which leads to fetal exposure to indoor air \u003csup\u003e\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e\u003c/sup\u003e.Young children are more vulnerable to environmental stressors due to their higher metabolic rate, greater air intake per unit of body weight, and the ongoing development of their respiratory systems \u003csup\u003e\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e\u003c/sup\u003e. Asthma and allergies are among the most common childhood diseases globally, posing a major health concern due to their high economic burden and negative impact on quality of life \u003csup\u003e\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e\u003c/sup\u003e. Given the importance of indoor air quality and its effects on health, assessing indoor air quality is a vital issue for protecting the health of the general public and should be prioritized in sensitive environments such as hospitals \u003csup\u003e\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e\u003c/sup\u003e. Studies have shown that 80\u0026ndash;90% of hospital infections are transmitted through direct contact, with 10\u0026ndash;20% of them are airborne \u003csup\u003e\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e\u003c/sup\u003e. It has been reported that 14 to 17 percent of all hospital infections are associated with poor air quality \u003csup\u003e\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e\u003c/sup\u003e. Pollutants such as PM\u003csub\u003e2.5\u003c/sub\u003e (Particulate matter with aerodynamic diameter less than 2.5 micrometers(, VOCs) Volatile organic compounds(, and CO₂)Carbon dioxide( are more common indoorair pollutants, and these pollutants are more closely associated with indoor activities \u003csup\u003e\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e\u003c/sup\u003e. Particles, including fine particles (PM\u003csub\u003e2.5\u003c/sub\u003e), are released indoors due to people's walking and outdoor sources \u003csup\u003e\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e\u003c/sup\u003e. Bioaerosols, a class of airborne pollutants, are often linked to biological compounds. This definition encompasses mycotoxins, peptidoglycans, viruses, high molecular weight allergens, pollen, and any other harmful or harmless bacteria and fungi, whether they are alive or dead \u003csup\u003e\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e\u003c/sup\u003e. Bioaerosols are able to travel great distances via the wind because of their tiny size and light weight, which might result in both acute and chronic illnesses in people, plants, and animals. The majority of bioaerosols are either produced by human activities or originate naturally \u003csup\u003e\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003eContaminants can enter interior spaces through ventilation systems when outdoor air pollution rises, having a big impact on indoor air quality. The design and operation of these systems are essential to maintaining healthy indoor environments \u003csup\u003e\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e\u003c/sup\u003e. The term ventilation refers to the process by which indoor air pollutants are diluted and removed, resulting in clean, breathable air \u003csup\u003e\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e\u003c/sup\u003e. There are three main types of ventilation systems used in hospitals: natural, mechanical, and combination \u003csup\u003e\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e\u003c/sup\u003e. Natural ventilation makes use of environmental forces, such as wind and temperature differences between indoor and outdoor air, to move air through openings such as windows and doors \u003csup\u003e\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e\u003c/sup\u003e. Mechanical ventilation employs fans to supply or exhaust air and can be set up in windows, walls, or duct systems \u003csup\u003e\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e\u003c/sup\u003e. Combined ventilation combines both natural and mechanical techniques to maximize airflow. This hybrid strategy has a number of benefits, such its ability to adapt to different climates, its energy efficiency, and its system flexibility \u003csup\u003e\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003eThe air exchange rate is an important factor for evaluating the efficiency of the ventilation system \u003csup\u003e\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e\u003c/sup\u003e. The ventilation rate in healthcare facilities is expressed in terms of air change per hour (ACH) and indicates how quickly the air inside the building is replaced with outside air (or processed air). The air change rate (ACH) is defined as the airflow inside the room divided by the volume of that space \u003csup\u003e\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e\u003c/sup\u003e. For example, if the amount of incoming and outgoing air in one hour equals the total volume of the space, it is said that one air change per hour has occurred in that space \u003csup\u003e\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003eThe healthcare facility is considered a critical area. Compared to other public places, the air quality within its various wards is more important since workers, particularly patients, are exposed to chemical and biological pollutants due to their weakened immune systems. Rezaei and colleagues \u003csup\u003e\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e\u003c/sup\u003e conducted a study to determine the density of airborne bacteria at the Children's Medical Center. In this study, only the infectious, pediatric surgery, blood, and oncology wards were examined. They only examined the microbial quality of the air inside the hospital. Dehghani and colleagues \u003csup\u003e\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e\u003c/sup\u003e examined the concentration of suspended particles in outdoor and indoor air and determined the correlation between them at Hafiz Hospital in Shiraz. Previous studies have only examined one of the parameters related to indoor air quality. Additionally, previous studies have not examined the type of ventilation system, the measurement of air changes per hour, and their impact on indoor air quality. Because there is little information about the quantity and quality of pollutants present in the indoor air of the children's medical center, and given the importance of examining the ventilation status in the hospital, particularly in areas such as the isolation room, operating room, and so on, conducting this study seems necessary. The aim of this study is to examine the indoor air quality and ventilation status of the hospital wards. In this study, we examine bioaerosols, PM\u003csub\u003e10\u003c/sub\u003e, PM\u003csub\u003e2.5\u003c/sub\u003e, and PM\u003csub\u003e1\u003c/sub\u003e concentration, as well as their quantity in the air, air exchange rate per hour and the CO\u003csub\u003e2\u003c/sub\u003e concentration in the air.\u003c/p\u003e"},{"header":"2. Materials and methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\u003ch2\u003e2.1. Study area and schedule\u003c/h2\u003e\u003cp\u003eThe construction of the Children's Medical Center was proposed in 1958 and opened in 1967. Initially, the hospital operated with departments for infectious diseases, nephrology, hematology, endocrinology, surgery, emergency, and specialized clinics. Gradually, departments for cardiology, neonatology, rheumatology, neurology, and others were added to this complex. Today, the Children's Medical Center operates as a reference hospital for children with over 350 active beds. This hospital is located in the Imam Khomeini Hospital Complex. The Imam Khomeini Hospital Complex is situated in the southwest of District 6 of Tehran city, Iran, at coordinates 35\u0026deg;42'21\" N and 51\u0026deg;22'57\" W (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). The surrounding areas of the Imam Khomeini Hospital Complex are mostly residential. The entrance to this hospital is located on Dr. Gharib Street.. The first sampling phase began on May 6, 2024. The second phase of sampling began on November 1, 2024. In this study, the Testo 440 device was used to determine the concentration of carbon dioxide gas in ppm, temperature in \u003csup\u003eo\u003c/sup\u003eC, and humidity in percentage \u003csup\u003e\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e\u003c/sup\u003e. In this study, the first sampling phase (from May to August) and the second sampling phase (from November to December) will be referred to as the warm and cold seasons for convenience.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec4\" class=\"Section2\"\u003e\u003ch2\u003e2.2. Data collection form\u003c/h2\u003e\u003cp\u003eTo conduct this study, the necessary arrangements were first made with the Children's Medical Center located in the Imam Khomeini Hospital Complex. A data collection form was prepared for each sampling point. This data collection form, designed to assess the indoor air quality at the Children's Medical Center, records the sampling date, sampling location, sampling time, carbon dioxide concentration, temperature, humidity, area of the sampling location, height of the sampling location, type of ventilation system used, window area, Window opening area, number of people present in the room, air flow rate due to natural ventilation if present, air flow rate due to mechanical ventilation if present, area of the air intake vent (in mechanical ventilation, these vents are usually installed on walls or ceilings, and in natural ventilation, this area is the same as the window area), and the shape of the air intake vent.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec5\" class=\"Section2\"\u003e\u003ch2\u003e2.3. Selected wards\u003c/h2\u003e\u003cp\u003eThe selected wards in this research include the endocrinology and nephrology department, hemodialysis, and infectious diseases department located in building number one; the general and cardiac operating rooms, emergency room, NICU, and heart and lung department located in building number two; and the bone marrow transplant and immunology and rheumatology department located in building number three. In selecting the sampling locations, efforts were made to choose wards from all three buildings of the Children's Medical Center based on their importance and high traffic. Additionally, the type of ventilation system used in these wards and whether the building is old or new were considered. In each ward, isolation rooms, if available, and then the busiest and most frequented inpatient rooms were selected for sampling. Figure\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e shows the map of selected wards for sampling at the Children's Medical Center.\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"No\" id=\"Taba\" border=\"1\"\u003e\u003ccolgroup cols=\"6\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eCharacteristics of selected wards for sampling\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003ewards\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eThe floor\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eBuilding\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eNumber of people\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003eType of ventilation system\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c6\"\u003e\u003cp\u003eDate of sampling\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eHeart and lung ward\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eFourth\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003eNatural and mechanical\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e16 June 2024, 26 November 2024\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eEmergency Room\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003ebasement\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e80\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003eNatural and mechanical\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e12 May 2024,\u003c/p\u003e\u003cp\u003e3 November 2024\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eOperating Room\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eSecond\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003emechanical\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e22 June 2024, 4 December 2024\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eNewborns\u003c/b\u003e\u003c/p\u003e\u003cp\u003e\u003cb\u003eintensive Care Unit\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eFourth\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e11\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003eNatural and mechanical\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e20 May 2024,\u003c/p\u003e\u003cp\u003e28 October 2024\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003ebone marrow transplant\u003c/b\u003e\u003c/p\u003e\u003cp\u003e\u003cb\u003eward\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eFirst\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003emechanical\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e30 June 2024, 23 December 2024\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eimmunology and rheumatology ward\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eThird\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003eNatural\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e11 June 2024,\u003c/p\u003e\u003cp\u003e16 November 2024\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eendocrinology and nephrology ward\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eSecond\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e6\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003eNatural\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e22 October 2024,\u003c/p\u003e\u003cp\u003e6 May 2024\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003einfectious diseases ward\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eFirst\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e6\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003eNatural and mechanical\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e16 June 2024, 20 November 2024\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003ehemodialysis\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eSecond\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e12\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003eNatural\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e22 October 2024,\u003c/p\u003e\u003cp\u003e6 May 2024\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec6\" class=\"Section2\"\u003e\u003ch2\u003e2.4. Air Quality Measurment\u003c/h2\u003e\u003cp\u003eFor this study, the equipment was taken to the Children's Medical Center every 6 days, and each ward was examined on the respective date.\u003c/p\u003e\u003cdiv id=\"Sec7\" class=\"Section3\"\u003e\u003ch2\u003e2.4.1. ACH\u003c/h2\u003e\u003cp\u003eTo calculate the air changes per hour, the length, width, and height of the room or sampling location must be measured in meters. To calculate the flow rate of air entering the space through a window or air handling unit, the area of the window or air inlet to the room must also be determined based on its geometric shape by measuring its length and width or calculating the diameter or radius of a circle. After calculating the dimensions of the room and the air inlet to determine the flow rate entering or exiting the room, it is necessary to measure the air velocity in m/s. For this purpose, we used the VT 115 KIMO Hotwire thermo-anemometer, which measures air velocity in m/s \u003csup\u003e22\u003c/sup\u003e. To increase the accuracy of measuring air flow speed, we performed this operation in the corners, at the edges of the window at every 10 cm interval, and at the center of the window at 10 cm intervals. Additionally, to measure the airflow velocity exiting the vents, we also took measurements at the center and edges. Then we calculate the average of the measured values for each window or air inlet.\u003c/p\u003e\u003cp\u003eAfter calculating the air flow velocity in meters per second, we use the following formula to calculate the inlet or outlet flow rate (Eq.\u0026nbsp;1).\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"No\" id=\"Tabb\" border=\"1\"\u003e\u003ccolgroup cols=\"2\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cem\u003eQ(m\u0026sup3;/s)\u0026thinsp;=\u0026thinsp;V(m/s) \u0026times; Area (m\u0026sup2;)\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e(Eq.\u0026nbsp;1)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eAfter calculating the flow rate, we can determine the air change per hour by calculating the volume of the room or space in equation (Eq.\u0026nbsp;2).\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"No\" id=\"Tabc\" border=\"1\"\u003e\u003ccolgroup cols=\"2\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cem\u003eRoom volume (m\u0026sup3;)\u0026thinsp;=\u0026thinsp;length (m) \u0026times; width (m) \u0026times; height (m)\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e(Eq.\u0026nbsp;2)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eThen, according to the following formula (Eq.\u0026nbsp;3), we calculate ACH \u003csup\u003e\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e, \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e\u003c/sup\u003e:\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"No\" id=\"Tabd\" border=\"1\"\u003e\u003ccolgroup cols=\"2\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:ACH=\\frac{Q\\left(\\frac{{m}^{3}}{\\text{s}}\\right)}{\\:\\text{R}\\text{o}\\text{o}\\text{m}\\:\\text{v}\\text{o}\\text{l}\\text{u}\\text{m}\\text{e}\\left({m}^{3}\\right)\\:\\:\\:}\\)\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e(Eq.\u0026nbsp;3)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec8\" class=\"Section3\"\u003e\u003ch2\u003e2.4.2. Temp, CO\u003csub\u003e2\u003c/sub\u003e, Humidity\u003c/h2\u003e\u003cp\u003eTo measure temperature, relative humidity, and CO₂ concentration, the Testo 440 device was used. The Testo 440 device can measure various environmental parameters depending on the type of probe used \u003csup\u003e\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec9\" class=\"Section3\"\u003e\u003ch2\u003e2.4.3. PM measurement\u003c/h2\u003e\u003cp\u003eIn this study, the PLANTOWER PMS 5003 device (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e) was used to measure the concentration and number of particles \u003csup\u003e\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e\u003c/sup\u003e. This device is capable of reporting the PM\u003csub\u003e10\u003c/sub\u003e, PM\u003csub\u003e2.5\u003c/sub\u003e, and PM\u003csub\u003e1\u003c/sub\u003e concentration in micrograms per cubic meter. It also reports the number of particles smaller than 0.5, 1, 2.5, 5, and 10 micrometers in terms of number per liter \u003csup\u003e\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e\u003c/sup\u003e. The principle of laser scattering is applied in these sensors. This means they shine a laser on particles in the air, then gather the scattered light to a certain degree, eventually creating a graph that shows how the intensity of scattered light changes over time. Finally, the equivalent diameter of the particles and the number of particles with different diameters per unit volume can be calculated based on MIE theory (Mie theory, commonly referred to as Lorenz-Mie theory, is a mathematical approach used to explain how electromagnetic waves scatter when they encounter spherical particles.) by a microprocessor \u003csup\u003e\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e\u003c/sup\u003e. The manufacturer determines the particle size using an unidentified algorithm. The PMS5003's fan forces air through it at 0.1 L m-1, and its laser runs at 680 nm \u003csup\u003e24\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eThese sensors were placed at a height of 100\u0026ndash;150 centimeters from the ground during sampling. To prevent underestimating the concentration of particles, these sensors were not placed in front of air vents, windows, or air conditioning ducts.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec10\" class=\"Section3\"\u003e\u003ch2\u003e2.4.4. Bioaerosol measurement\u003c/h2\u003e\u003cp\u003eIn this study, we also used TSA culture medium. To prepare the desired culture medium, we followed the instructions mentioned on the container holding the culture medium. To prepare 1000 milliliters of TSA culture medium, it is necessary to dissolve 40 grams of it in 1000 milliliters of distilled water. The culture medium used in this study was powdered. According to the manufacturer's instructions, it is necessary to heat the culture medium in distilled water for one minute after it has dissolved. This step was performed using a heater. After completing this stage, we transfer the culture medium into screw-cap bottles. We place the bottle inside the autoclave and set it at a temperature of 121 \u003csup\u003eo\u003c/sup\u003eC and a pressure of 15 psi for 15 minutes. After 15 minutes, the culture medium has been sterilized. For passive sampling in this method, we used a 9-centimeter diameter plate. After the temperature of the prepared culture medium decreased, we disinfected the work surface with 70% alcohol. In this study, all steps of distributing the culture medium were performed under the hood. After evenly spreading the culture medium in the plates, we wait for the agar to solidify. Then, we placed the lid on the culture medium and stored it upside down in a sterile refrigerator until use.\u003c/p\u003e\u003cp\u003eAfter preparing the plates containing the desired culture medium under sterile conditions, we randomly selected a few of them and placed them in the incubator at a temperature of 37 \u003csup\u003eo\u003c/sup\u003eC for 24 hours. The plates were transferred to the sampling site under sterile conditions. After the sampling was completed, the culture media used for sampling were transferred to the laboratory in a cooler with ice at a temperature between 0 and 4 \u003csup\u003eo\u003c/sup\u003eC. The plates were immediately placed upside down in an incubator at 37 \u003csup\u003eo\u003c/sup\u003eC, and after 24 and 48 hours, the colonies formed on the culture medium were counted and examined using a colony counter.\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv id=\"Sec11\" class=\"Section2\"\u003e\u003ch2\u003e2.5. Statistical analysis\u003c/h2\u003e\u003cp\u003eIn this study, we reported only one value for the number of counted colonies, the concentration of benzene, toluene, ethylbenzene, and xylene. However, since the sensors used for measuring concentration and particle count provide us with 5 data points per minute, we used the mean, maximum, minimum, and standard deviation indices to better report the obtained results.\u003c/p\u003e\u003cp\u003eFor air change per hour, we also calculated the mean, minimum, and maximum air changes per hour. Additionally, to examine the correlation between concentration, particle count, and the number of colonies counted in the hospital air and outdoor air, we first need to check the normality of the data in question. To check the normality of the data, we used the Shapiro-Wilk test. This test checks whether a dataset follows a normal distribution or not. After conducting this test, it was determined that the obtained data do not follow a normal distribution. As a result, Spearman correlation, which does not require a linear relationship or normal data distribution, was used to examine the correlation.\u003c/p\u003e\u003cp\u003eTo calculate the Spearman correlation coefficient and also to perform the Shapiro-Wilk test and other statistical analyses, we used R software version 4.2.1 and Microsoft Excel 2021.\u003c/p\u003e\u003c/div\u003e"},{"header":"3. Results and Discussion","content":"\u003cp\u003eIn order to enhance the reporting of the findings, we organized the chosen wards according to their utilization within the hospital. During the warm season, the classification according to utilization comprises the emergency department, patient admission rooms, critical care units, sterile transplant facilities, surgical suites, nursing stations, diagnostic laboratories, and hemodialysis units. During the winter season, the classification according to utilization encompasses the emergency department, patient admission rooms, critical care unit, sterile transplant facilities, surgical suite, and hemodialysis units.\u003c/p\u003e\u003cp\u003eAccording to Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e ( a\u0026amp;b), the highest average PM\u003csub\u003e1\u003c/sub\u003e concentration is observed in the emergency ward (18 \u0026micro;g/m\u0026sup3;) and inpatient rooms (26 \u0026micro;g/m\u0026sup3;) during the warm and cold seasons, respectively.In the warm season, after the emergency ward, the highest PM\u003csub\u003e1\u003c/sub\u003e concentration is in the inpatient rooms (12 \u0026micro;g/m\u0026sup3;), which could be due to the density of people, poor ventilation and the opening and closing of doors and windows.In the cold season, after the inpatient rooms, the emergency ward (25 \u0026micro;g/m\u0026sup3;) has the highest PM\u003csub\u003e1\u003c/sub\u003e concentration. Additionally, the lowest average concentration of PM\u003csub\u003e1\u003c/sub\u003e in both the warm and cold seasons was observed in the clean rooms of the transplant unit (0 \u0026micro;g/m\u0026sup3;). The reason for the decrease in PM\u003csub\u003e1\u003c/sub\u003e concentration in the clean rooms of the transplant ward is the presence of a high-efficiency HEPA filter under the air intake vent to the ward. Additionally, the clean rooms had positive pressure, and the airflow direction in these spaces was from the interior of the ward toward the hallways and other areas.The distribution of data in the emergency room and inpatient room is broader, indicating high variance in particle concentration. This issue could indicate fluctuations in ventilation performance or high population density. The average PM\u003csub\u003e1\u003c/sub\u003e concentration in the winter season in the emergency ward and inpatient rooms is higher than the average PM\u003csub\u003e1\u003c/sub\u003e concentration in the summer season in the same areas.The reason for the increase in PM\u003csub\u003e1\u003c/sub\u003e concentration in the cold season may be related to the increase in the concentration of suspended particles, including PM\u003csub\u003e1\u003c/sub\u003e, in the outdoor air.\u003c/p\u003e\u003cp\u003eFurthermore, the emergency room (30 \u0026micro;g/m\u0026sup3;) has the highest average PM\u003csub\u003e2.5\u003c/sub\u003e concentration during the warm season, while the inpatient rooms (44 \u0026micro;g/m\u0026sup3;) have the highest average PM\u003csub\u003e2.5\u003c/sub\u003e concentration during the cold season (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e (c \u0026amp; d)). Due to the large number of patients and regular disinfection in the emergency room, the PM\u003csub\u003e2.5\u003c/sub\u003e concentration is probably higher than in other areas. The emergency room (39 \u0026micro;g/m\u0026sup3;) has the highest average PM\u003csub\u003e10\u003c/sub\u003e concentration during the warm season, while the inpatient rooms (53 \u0026micro;g/m\u0026sup3;) have the highest average concentration of PM\u003csub\u003e10\u003c/sub\u003e during the cold season (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e (e \u0026amp; f)). In the pediatric surgery, operating room, and emergency room of the hospital, Shahid Uz Zaman and colleagues reported the average PM\u003csub\u003e1\u003c/sub\u003e, PM\u003csub\u003e2.5\u003c/sub\u003e, and PM\u003csub\u003e10\u003c/sub\u003e concentrations during the warm season to be 48.25 \u0026micro;g/m\u0026sup3;, 64.00 \u0026micro;g/m\u0026sup3;, and 73.75 \u0026micro;g/m\u0026sup3;, respectively; 44.50 \u0026micro;g/m\u0026sup3;, 59.25 \u0026micro;g/m\u0026sup3;, and 68.25 \u0026micro;g/m\u0026sup3;; and 29.17 \u0026micro;g/m\u0026sup3;, 39.00 \u0026micro;g/m\u0026sup3;, and 45.17 \u0026micro;g/m\u0026sup3; \u003csup\u003e26\u003c/sup\u003e. Shahid Uz Zaman and colleagues found that the average concentrations of PM\u003csub\u003e1\u003c/sub\u003e, PM\u003csub\u003e2.5\u003c/sub\u003e, and PM\u003csub\u003e10\u003c/sub\u003e were higher during the warm season than in the current investigation. The PM\u003csub\u003e2.5\u003c/sub\u003e concentration in the indoor environment of each hospital is positively correlated with the PM\u003csub\u003e2.5\u003c/sub\u003e concentration in the outdoor environment. The concentration may also be influenced by factors like the number of people present, the ambient temperature, the size of the room, and the number of windows and doors. Furthermore, the concentration of suspended particles in both indoor and outdoor settings may depend on wind speed \u003csup\u003e\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e\u003c/sup\u003e. Hand washing at sinks, utilizing medical sprays, carrying out nebulizations, making beds, and cleaning activities are examples of actions that can directly impact the concentration of airborne particles inside hospitals \u003csup\u003e\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003eThe average PM\u003csub\u003e2.5\u003c/sub\u003e concentration in the hospitals they studied was reported as 52.28 \u0026micro;g/m\u003csup\u003e3\u003c/sup\u003e and 222.353 \u0026micro;g/m\u003csup\u003e3\u003c/sup\u003e in the fall and winter seasons, respectively \u003csup\u003e\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e\u003c/sup\u003e. The average PM\u003csub\u003e2.5\u003c/sub\u003e concentration in the cold and warm seasons at the Children's Medical Center was 32 \u0026micro;g/m\u0026sup3; and 22 \u0026micro;g/m\u0026sup3;, respectively, which was lower compared to the study by Shahid Uz Zaman and colleagues. In a study, the median PM\u003csub\u003e2.5\u003c/sub\u003e concentration in the warm season was higher than in the cold season \u003csup\u003e\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e\u003c/sup\u003e. The results of this study differ from the current study in the children's hospital. During the warm season, work areas in the hospital, including the clinic, clinic waiting area, reception, lobby, staff office, hallway, meeting room, and ophthalmology patient room, had PM\u003csub\u003e2.5\u003c/sub\u003e concentration levels higher than the standard recommended by WHO (25 \u0026micro;g/m\u003csup\u003e3\u003c/sup\u003e). The elevated levels of PM2. 5 and PM10 during the warm season can be linked to the presence of regional dust storms, as well as the increased population density and human activities in these locations \u003csup\u003e\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003eDerikvand and colleagues reported an average PM\u003csub\u003e2.5\u003c/sub\u003e concentration of 20\u0026ndash;233 \u0026micro;g/m\u0026sup3; in public places in Tehran. The highest average PM\u003csub\u003e2.5\u003c/sub\u003e concentration (233\u0026micro;g/m\u0026sup3;) was found in hookah cafes. The lowest average PM\u003csub\u003e2.5\u003c/sub\u003e concentration (20 \u0026micro;g/m3) was found in sports clubs. In this study, the average PM\u003csub\u003e2.5\u003c/sub\u003e concentration in the hospital was 21 \u0026micro;g/m\u0026sup3; \u003csup\u003e29\u003c/sup\u003e. The average PM\u003csub\u003e2.5\u003c/sub\u003e concentration in the cold and warm seasons at the Children's Medical Center was 32 \u0026micro;g/m\u0026sup3; and 22 \u0026micro;g/m\u0026sup3;, respectively, which was higher compared to the study by Derikvand et al \u003csup\u003e29\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003eThe number of particles less than 10, 2.5, and 1 micrometer in diameter per liter of indoor air during the warm and cold seasons is represented by the Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e. In the emergency room and inpatient rooms, respectively, the maximum number of particles less than 10, 2.5, and 1 micrometer per liter of air are found during the warm and cold seasons. Following that, the emergency department and inpatient rooms have the greatest number of particles in the warm and cold seasons that are less than 10, 2.5, and 1 micron in size per liter of air, respectively. In the transplant department's clean rooms, the fewest particles smaller than 10, 2.5, and 1 micron are seen in the warm and cold seasons (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e (a, b, c, d, e \u0026amp; d)). In every ward, the average number of particles smaller than 10 micrometers per liter of air is higher in the cold season than in the warm season. The temperature inversion in the cold season, followed by an increase in airborne suspended particles, is the cause of the higher concentration of suspended particles during the cold season as opposed to the warm one.\u003c/p\u003e\u003cp\u003eIn a study conducted in Malaysia, the number of particles smaller than 10, 5, and 0.5 micrometers per cubic meter of air was measured in 4 operating rooms. The number of particles smaller than 10 micrometers in the 4 operating rooms was reported as 225, 53, 293, and 41 particles per cubic meter of air, respectively \u003csup\u003e\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e\u003c/sup\u003e. In a study in the city of Qazvin, the number of particles smaller than 2.5 and 0.3 micrometers per cubic meter of air was measured in different sections of a hospital. They reported the highest number of particles smaller than 2.5 and 0.3 micrometers per cubic meter of air in the women's surgery and emergency sections \u003csup\u003e\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cdiv id=\"Sec13\" class=\"Section2\"\u003e\u003ch2\u003e3.1. The quantity and concentration of particles in the outdoor air\u003c/h2\u003e\u003cp\u003eThe PM\u003csub\u003e1\u003c/sub\u003e, PM\u003csub\u003e2.5\u003c/sub\u003e, and PM\u003csub\u003e10\u003c/sub\u003e concentration in the ambient air, measured in micrograms per cubic meter, is shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e. In the warm and cold seasons, the average PM\u003csub\u003e1\u003c/sub\u003e concentration is 12 \u0026micro;g/m\u003csup\u003e3\u003c/sup\u003e and 34 \u0026micro;g/m\u003csup\u003e3\u003c/sup\u003e, respectively. The average PM\u003csub\u003e2.5\u003c/sub\u003e concentrations during the warm and cold seasons are 18 \u0026micro;g/m\u003csup\u003e3\u003c/sup\u003e and 56 \u0026micro;g/m\u003csup\u003e3\u003c/sup\u003e, respectively. The average PM\u003csub\u003e10\u003c/sub\u003e concentration is 20 \u0026micro;g/m\u003csup\u003e3\u003c/sup\u003e during the warm season and 66 \u0026micro;g/m\u003csup\u003e3\u003c/sup\u003e during the cold season. The average PM\u003csub\u003e1\u003c/sub\u003e, PM\u003csub\u003e2.5\u003c/sub\u003e, and PM\u003csub\u003e10\u003c/sub\u003e concentration has been higher during the cold season than during the warm season. The higher concentration of airborne suspended particles in outdoor air during the cold season may be due to the air inversion in the cold season and the increase in the concentration of airborne suspended particles. Shahid Uz Zaman and colleagues reported the average concentrations of PM\u003csub\u003e1\u003c/sub\u003e, PM\u003csub\u003e2.5\u003c/sub\u003e, and PM\u003csub\u003e10\u003c/sub\u003e in outdoor air during the warm and cold seasons in three hospitals as 49.05 \u0026micro;g/m\u0026sup3;, 65.47 \u0026micro;g/m\u0026sup3;, and 75.47 \u0026micro;g/m\u0026sup3; and 188.80 \u0026micro;g/m\u0026sup3;, 248.92 \u0026micro;g/m\u0026sup3;, and 288.33 \u0026micro;g/m\u0026sup3;, respectively \u003csup\u003e\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e\u003c/sup\u003e. In comparison to the current study conducted at the children's hospital, Shahid Uz Zaman and colleagues' research conducted across three hospitals in the warm and cold seasons yielded superior results.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eFigure\u0026nbsp;4 relates to the number of particles smaller than 10, 2.5, and 1 micrometer per liter of air during the warm and cold seasons in the open air. The average number of particles smaller than 10, 2.5, and 1 micrometer per liter of air during the cold season is higher than in the warm season.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec14\" class=\"Section2\"\u003e\u003ch2\u003e3.2. Air change per hour(ACH)\u003c/h2\u003e\u003cp\u003eTable\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e displays the minimum, average, and maximum air changes per hour (ACH) for specific areas in the children's hospital, tracked during both warm and cold seasons. The most notable average ACH during the warm season was noted in the Intensive Care Unit (ICU), followed closely by the clean rooms in the transplant ward. Conversely, the emergency department reported the lowest average ACH for this period (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e5\u003c/span\u003e (a)).\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eMinimum, average and maximum air changes per hour in selected wards during the warm and cold season in a children's hospital\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"11\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c9\" colnum=\"9\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c10\" colnum=\"10\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c11\" colnum=\"11\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003esection\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colspan=\"2\" nameend=\"c3\" namest=\"c2\"\u003e\u003cp\u003eACH\u003csub\u003emin\u003c/sub\u003e\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e\u003cp\u003eACH\u003csub\u003eave\u003c/sub\u003e\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colspan=\"2\" nameend=\"c7\" namest=\"c6\"\u003e\u003cp\u003eACH\u003csub\u003emax\u003c/sub\u003e\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colspan=\"3\" nameend=\"c10\" namest=\"c8\"\u003e\u003cp\u003eType of ventilation system\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colspan=\"1\" nameend=\"c11\" namest=\"c11\"\u003e\u0026nbsp;\u003c/th\u003e\u003c/tr\u003e\u003ctr\u003e\u003cth align=\"left\" colspan=\"10\" nameend=\"c10\" namest=\"c1\"\u003e\u003cp\u003eWarm season\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colspan=\"1\" nameend=\"c11\" namest=\"c11\"\u003e\u0026nbsp;\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eEmergency\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c3\" namest=\"c2\"\u003e\u003cp\u003e3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e\u003cp\u003e5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c7\" namest=\"c6\"\u003e\u003cp\u003e9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"3\" nameend=\"c10\" namest=\"c8\"\u003e\u003cp\u003eNatural and mechanical\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"1\" nameend=\"c11\" namest=\"c11\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eInpatient rooms\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c3\" namest=\"c2\"\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e\u003cp\u003e18\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c7\" namest=\"c6\"\u003e\u003cp\u003e116\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"3\" nameend=\"c10\" namest=\"c8\"\u003e\u003cp\u003eNatural and mechanical\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"1\" nameend=\"c11\" namest=\"c11\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eOperating rooms\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c3\" namest=\"c2\"\u003e\u003cp\u003e1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e\u003cp\u003e9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c7\" namest=\"c6\"\u003e\u003cp\u003e21\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"3\" nameend=\"c10\" namest=\"c8\"\u003e\u003cp\u003emechanical\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"1\" nameend=\"c11\" namest=\"c11\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eclean rooms\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c3\" namest=\"c2\"\u003e\u003cp\u003e6\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e\u003cp\u003e46\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c7\" namest=\"c6\"\u003e\u003cp\u003e121\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"3\" nameend=\"c10\" namest=\"c8\"\u003e\u003cp\u003emechanical\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"1\" nameend=\"c11\" namest=\"c11\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eIntensive Care Unit\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c3\" namest=\"c2\"\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e\u003cp\u003e51\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c7\" namest=\"c6\"\u003e\u003cp\u003e429\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"3\" nameend=\"c10\" namest=\"c8\"\u003e\u003cp\u003eNatural and mechanical\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"1\" nameend=\"c11\" namest=\"c11\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eHemodialysis\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c3\" namest=\"c2\"\u003e\u003cp\u003e2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e\u003cp\u003e16\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c7\" namest=\"c6\"\u003e\u003cp\u003e46\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"3\" nameend=\"c10\" namest=\"c8\"\u003e\u003cp\u003enatural\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"1\" nameend=\"c11\" namest=\"c11\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colspan=\"10\" nameend=\"c10\" namest=\"c1\"\u003e\u003cp\u003e\u003cb\u003eCold season\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"1\" nameend=\"c11\" namest=\"c11\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eEmergency\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c3\" namest=\"c2\"\u003e\u003cp\u003e1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e\u003cp\u003e4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c7\" namest=\"c6\"\u003e\u003cp\u003e7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"3\" nameend=\"c10\" namest=\"c8\"\u003e\u003cp\u003eNatural and mechanical\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"1\" nameend=\"c11\" namest=\"c11\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colspan=\"3\" nameend=\"c3\" namest=\"c1\"\u003e\u003cp\u003eInpatient rooms\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c7\" namest=\"c6\"\u003e\u003cp\u003e3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c9\" namest=\"c8\"\u003e\u003cp\u003e31\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u003cp\u003eNatural and mechanical\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"1\" nameend=\"c11\" namest=\"c11\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colspan=\"3\" nameend=\"c3\" namest=\"c1\"\u003e\u003cp\u003eOperating rooms\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c7\" namest=\"c6\"\u003e\u003cp\u003e1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c9\" namest=\"c8\"\u003e\u003cp\u003e2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u003cp\u003emechanical\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"1\" nameend=\"c11\" namest=\"c11\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colspan=\"3\" nameend=\"c3\" namest=\"c1\"\u003e\u003cp\u003eclean rooms\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e\u003cp\u003e1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c7\" namest=\"c6\"\u003e\u003cp\u003e22\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c9\" namest=\"c8\"\u003e\u003cp\u003e72\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u003cp\u003emechanical\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"1\" nameend=\"c11\" namest=\"c11\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colspan=\"3\" nameend=\"c3\" namest=\"c1\"\u003e\u003cp\u003eIntensive Care Unit\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e\u003cp\u003e5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c7\" namest=\"c6\"\u003e\u003cp\u003e44\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c9\" namest=\"c8\"\u003e\u003cp\u003e115\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u003cp\u003eNatural and mechanical\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"1\" nameend=\"c11\" namest=\"c11\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colspan=\"3\" nameend=\"c3\" namest=\"c1\"\u003e\u003cp\u003eHemodialysis\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e\u003cp\u003e1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c7\" namest=\"c6\"\u003e\u003cp\u003e5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c9\" namest=\"c8\"\u003e\u003cp\u003e13\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u003cp\u003enatural\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"1\" nameend=\"c11\" namest=\"c11\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eDuring the cold season, the ICU and clean rooms again recorded the highest average ACH, whereas the operating room experienced the lowest (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e5\u003c/span\u003e (b)\u003cb\u003e)\u003c/b\u003e. In general, the average ACH across all selected wards was higher in the warm months than in the cold months.\u003c/p\u003e\u003cp\u003eElements such as the size of the rooms, the number and size of openable windows, and their arrangement played a crucial role in enhancing the ACH. In this research, the choice of utilizing natural ventilation was left up to the patients. With favorable weather from May to August, windows could be fully opened, greatly boosting the ACH during warmer months.\u003c/p\u003e\u003cp\u003eAlthough natural ventilation can significantly improve ACH, it may also lead to the ingress of particles and other outdoor pollutants into the indoor environment. Additionally, an ACH that exceeds 20 times per hour could result in too much airflow disruption and raise ventilation expenses. Reliable sources suggest that an ideal ACH should be around 12 times per hour \u003csup\u003e\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003eAs a result, during the warm season, the average ACH in both the emergency ward and operating room fell short of the suggested value. In the cold season, the emergency ward, inpatient rooms, operating room, and hemodialysis unit also had an average ACH that was below the recommended limit.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eThe average air exchange rate per hour in selected wards of the Children's Medical Center during the warm season was 24 times per hour. Additionally, the average air exchange rate per hour in selected wards of the Children's Medical Center during the cold season was 12 times per hour. In comparison to the warm season, the average air exchange rate per hour fell during the cold season. The reason for the decrease in the air exchange rate per hour in the cold season compared to the warm season is the lack of natural and mechanical ventilation in the ward due to the drop in temperature. The recommended air exchange rate per hour for the operating room is 15 times per hour \u003csup\u003e\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e, \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e\u003c/sup\u003e. The hourly air exchange rate in the operating room during both the cold and warm seasons fell short of the suggested standards.\u003c/p\u003e\u003cp\u003eThe simultaneous use of natural and mechanical ventilation in hospital wards, although it increases the air exchange rate per hour, will lead to energy waste and increased costs related to cooling and heating systems in each ward. Since only the transplant and operating room wards use return air from the ward for re-ventilation, not using return air will result in a significant waste of energy. Since the air entering the air handling system requires cooling in the summer and heating in the winter, increased use of mechanical ventilation will lead to energy waste \u003csup\u003e\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e\u003c/sup\u003e. Huiyi Tan and colleagues reported the air exchange rates per hour for operating rooms 1, 2, 3, and 4 as 40, 33, 29, and 32, respectively \u003csup\u003e\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e\u003c/sup\u003e. The average air changes per hour in the operating room in the present study were 8.8 and 0.7 air changes per hour in the warm and cold seasons, respectively. The average air exchange per hour in the study by Huiyi Tan and colleagues was higher compared to the present study.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec15\" class=\"Section2\"\u003e\u003ch2\u003e3.3. Temperature, humidity, and carbon dioxide concentration\u003c/h2\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eChart 6 shows the concentration of CO2 in various hospital wards during the warm and cold seasons. During the warm season, the highest average concentration is observed in the emergency ward (436 ppm), followed by inpatient rooms (355 ppm), and the lowest in clean transplant rooms (65.8 ppm) (Fig 6 (a)). During the cold season, carbon dioxide average concentration rise in inpatient rooms (490 ppm) and fall to their lowest point in the hemodialysis (67 ppm) (Fig 6 (b)). The low concentration of carbon dioxide in the clean transplant rooms could be attributed to the small number of occupants - only one person is usually present. Furthermore, the presence of opposing windows and a larger air exchange rate per hour in the hemodialysis part contribute to the area's lower CO2 levels.\u003c/p\u003e\u003cp\u003eThe average CO\u003csub\u003e2\u003c/sub\u003e concentration at the Children's Medical Center during the warm season was 270 ppm. Additionally, the average CO\u003csub\u003e2\u003c/sub\u003e concentration at the Children's Medical Center during the cold season was 390 ppm. The average CO\u003csub\u003e2\u003c/sub\u003e concentration in the children's medical center during the warm season was lower compared to the cold season. The reason for the increase in CO\u003csub\u003e2\u003c/sub\u003e concentration in the cold season is that the average air exchange rate per hour in the cold season has decreased compared to the warm season. The average CO\u003csub\u003e2\u003c/sub\u003e concentration in the winter and summer seasons in the Rennes and Nancy hospitals in France is 498 ppm and 411 ppm and 548 ppm and 479 ppm, respectively \u003csup\u003e\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e\u003c/sup\u003e. The average CO\u003csub\u003e2\u003c/sub\u003e concentration in the Children's Medical Center during the warm season was 270 ppm, which was lower compared to the Rennes and Nancy hospitals. The average CO\u003csub\u003e2\u003c/sub\u003e concentration in the Children's Medical Center during the cold season was 390 ppm, which was lower compared to the Rennes and Nancy hospitals.\u003c/p\u003e\u003cp\u003eChamseddine A and colleagues \u003csup\u003e\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e\u003c/sup\u003e found that the hospital clinic area had the highest concentration of carbon dioxide gas throughout both the warm and cold seasons. They also found the lowest concentration of carbon dioxide gas in the pediatric rooms and emergency department during the warm and cold seasons, respectively \u003csup\u003e\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e\u003c/sup\u003e. The findings of Chamseddine A's study do not correspond to the current study at the Children's Medical Center. The average number of people present in the selected departments during the warm season was 11. During the cold season, the selected sections had an average population of 12 persons. During the cold season, the average number of individuals in each region increased compared to the warm season, potentially contributing to the rise in CO\u003csub\u003e2\u003c/sub\u003e concentrations.\u003c/p\u003e\u003cp\u003eCarbon dioxide is a byproduct of human metabolism and is present in large amounts in human exhalation. The average concentration of carbon dioxide in the exhaled air of individuals is around 40,000 ppm. The concentration of carbon dioxide gas is directly related to the ventilation rate in enclosed spaces. In a clinical space with good ventilation, the CO\u003csub\u003e2\u003c/sub\u003e concentration in most areas is less than 400 ppm \u003csup\u003e\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e\u003c/sup\u003e. The concentration of CO\u003csub\u003e2\u003c/sub\u003e gas should not exceed 1000 ppm, and its average concentration should be less than or equal to 500 ppm \u003csup\u003e\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e\u003c/sup\u003e. Since the number of people in the emergency ward and inpatient rooms is high, the concentration of carbon dioxide gas in these areas increases.\u003c/p\u003e\u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e7\u003c/span\u003e shows the temperature in \u003csup\u003eo\u003c/sup\u003eC in selected wards during the warm and cold seasons. The highest average temperature in the warm season is observed in the clean rooms of the transplant ward (31\u003csup\u003eo\u003c/sup\u003eC). Additionally, the lowest average temperature in the warm season is observed in the hemodialysis ward (24 \u003csup\u003eo\u003c/sup\u003eC) (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e7\u003c/span\u003e (a)). The highest average temperature in the cold season is observed in the emergency ward (37 \u003csup\u003eo\u003c/sup\u003eC), and the lowest average temperature in the cold season is observed in the operating room(22 \u003csup\u003eo\u003c/sup\u003eC) (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e7\u003c/span\u003e (b)). To ensure the thermal comfort of patients in the hospital, maintaining temperature and humidity within specified ranges is important. The recommended values by ASHRAE 170 for temperature and humidity are 21\u0026ndash;24 \u003csup\u003eo\u003c/sup\u003eC and 40\u0026ndash;60%, respectively \u003csup\u003e\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e\u003c/sup\u003e. The average temperature in selected wards of the Children's Medical Center during the warm season has been 27\u0026deg;C. The average temperature in the cold season was 25\u0026deg;C. The average temperature in the cold season has been lower than in the warm season because the second sampling phase was conducted in the fall and winter, when the temperature is lower. Overall, the average temperature in the cold and warm seasons was higher than the standard amount.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eThe average temperature in the summer and winter seasons at the Rennes and Nancy hospitals was reported as 23.8\u0026deg;C and 23 \u003csup\u003eo\u003c/sup\u003eC, and 24.5 \u003csup\u003eo\u003c/sup\u003eC and 22 \u003csup\u003eo\u003c/sup\u003eC, respectively \u003csup\u003e\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e\u003c/sup\u003e. The average temperature measured in hospitals in France is lower than the average temperature measured at the children's medical center.\u003c/p\u003e\u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e8\u003c/span\u003e illustrates the humidity in selected wards during the warm and cold seasons. The highest and lowest average humidity in the warm season was observed in the operating room (40%) and intensive care unit (22%), respectively (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e8\u003c/span\u003e (a)). Also, the highest and lowest average humidity in the cold season was observed in the Inpatient rooms (36%) and hemodialysis unit (18%), respectively (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e8\u003c/span\u003e (b)).\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eThe average humidity in the selected sections of the Children's Medical Center during the warm season was 32%. The average humidity in the cold season was 31%. The typical humidity during the warm months is greater than that in the colder months, as the initial sampling took place in the spring and summer seasons.\u003c/p\u003e\u003cp\u003eThe measured humidity levels in hospitals A, B, C, and D were reported as 56.9\u0026ndash;72.6%, 52.6\u0026ndash;59.9%, 62.9\u0026ndash;77.9%, and 52.9\u0026ndash;67.8%, respectively \u003csup\u003e\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e\u003c/sup\u003e. The average humidity measured at the Children's Medical Center was lower compared to the four hospitals in Malaysia.\u003c/p\u003e\u003cp\u003eThe average humidity measured in the two hospitals, Rennes and Nancy, in the winter and summer seasons was 35.4% and 24.4% and 44.1% and 55.4%, respectively \u003csup\u003e\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e\u003c/sup\u003e. The average humidity in the warm season at the Children's Medical Center was lower compared to the two hospitals, Rennes and Nancy. The average humidity in the cold season at the Children's Medical Center was lower than at Rennes Hospital but higher than at Nancy Hospital.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec16\" class=\"Section2\"\u003e\u003ch2\u003e3.4. Bioaerosols\u003c/h2\u003e\u003cp\u003eFigure\u0026nbsp;9 relates to the number of colonies counted on each plate after 24 and 48 hours in selected wards of the Children's Medical Center during the warm and cold seasons. The highest number of colonies counted after 24 hours in both the warm and cold seasons is observed in the inpatient rooms (Fig.\u0026nbsp;9 (a \u0026amp; b)). The number of colonies counted in the inpatient rooms increased in the warm season compared to the cold season. Additionally, the lowest number of colonies counted after 24 hours in both the warm and cold seasons is observed in the clean transplant rooms (Fig.\u0026nbsp;9 (a \u0026amp; b)). The number of colonies counted after 24 hours in the clean transplant rooms increased in the warm season compared to the cold season.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eFive classes of the Airborne Microbial Pollution Index (IMA) have been defined: 0\u0026ndash;5 very good, 6\u0026ndash;25 good, 26\u0026ndash;50 moderate, 51\u0026ndash;75 poor, and more than 76 very poor. Another ranking has also been proposed for this index, where values of 5, 25, and 50 indicate moderate, high, and very high risk, respectively \u003csup\u003e\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e\u003c/sup\u003e. The average number of colonies counted in the cold and warm seasons at the Children's Medical Center is in good condition compared to the standards.\u003c/p\u003e\u003cp\u003eMara Di Giulio and colleagues reported the average number of colonies counted per plate during the period from April to June in buildings A, B, and C as 1.1\u0026ndash;8.41 CFU/plate/h, 0.5\u0026ndash;3.8 CFU/plate/h, and 1.1\u0026ndash;20.3 CFU/plate/h, respectively. The average number of colonies counted per plate during the October to December period in buildings A, B, and C were 0\u0026ndash;11 CFU/plate/h, 2.1\u0026ndash;5.7 CFU/plate/h, and 1.3\u0026ndash;17 CFU/plate/h, respectively. All measurements taken pertain to the morning time period \u003csup\u003e\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003eThe results of the study by Mara Di Giulio and colleagues showed that the microbial pollution index in the warm season was higher compared to the cold season. Since the temperature and relative humidity are higher in the warm seasons, it can lead to an increase in the air microbial pollution index during these periods. The microorganisms found in indoor air come not only from the activities of the people living there but also from polluted building materials and air from outside \u003csup\u003e\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e\u003c/sup\u003e. The results of the present study at the Children's Medical Center also showed that the average microbial pollution index in the warm season (21CFU/plate/h) was higher compared to the cold season (17CFU/plate/h), which is consistent with the study by Mara Di Giulio and colleagues.\u003c/p\u003e\u003cp\u003eErsel Sonmez and colleagues reported the number of bacterial colonies counted in the spring and summer before, during, and after the autopsy as 9.1 CFU/plate/h, 51.1 CFU/plate/h, 21.6 CFU/plate/h, 27.4 CFU/plate/h, 60.9 CFU/plate/h, and 19.7 CFU/plate/h, respectively. The results of this study showed that the number of bacterial and fungal colonies in the air of the autopsy room during the autopsy was significantly higher than before and after the autopsy. The temperature and humidity of the autopsy room had a significant impact on the growth of fungal colonies. In the summer, the temperature was higher and the humidity lower, which was associated with reduced fungal growth. The number of people present in the room and the number of autopsies had a direct impact on the number of bacterial colonies \u003csup\u003e\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e\u003c/sup\u003e. Buildings with a higher number of people have higher levels of suspended particles (PM), bacteria, and fungi. The increase in the number of people in an enclosed space leads to a significant rise in the concentration of bioaerosols (biological particles suspended in the air), with these concentrations reported to be 1.2 to 3.5 times higher than in conditions without people present \u003csup\u003e\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003eIn the present study at the Children's Medical Center, during the first and second sampling phases conducted in the warm and cold seasons, respectively, the number of counted colonies in the inpatient rooms increased with a higher number of patients. The results of both studies indicate that temperature and humidity play a significant role in the growth of microbial colonies. In the summer, higher temperatures were associated with increased bacterial growth and decreased fungal growth. In both studies, the number of individuals present in the room and the level of activity (such as the number of hospitalized patients or autopsies) were directly related to the increase in the number of microbial colonies.\u003c/p\u003e\u003cp\u003eDuring the summer season, the chosen areas of the Children's Medical Center had an average air exchange rate of 24 times per hour. Furthermore, during the cold season, the chosen areas of the Children's Medical Center had an average air exchange rate of 12 times per hour. The influx of fresh air into the room during the warm season may have contributed to the increase in the number of colonies counted in the chosen wards, as the air exchange rate per hour has increased in comparison to the cold season and the number of colonies counted in the open air during the warm season is higher than in the cold season.\u003c/p\u003e\u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e10\u003c/span\u003e relates to the number of colonies counted on each plate after 24 and 48 hours of incubation in the outdoor air during the warm and cold seasons. The number of colonies counted after 24 hours in the outdoor air during the warm season is higher than in the cold season (Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e10\u003c/span\u003e (a \u0026amp; b)). The reason for the increase in the number of colonies in the warm season compared to the cold season is the rise in temperature and humidity during the warm season.\u003c/p\u003e\u003cp\u003e\u003cb\u003e3.5 The correlation between the concentration and the number of particles in the hospital air and the outdoor air\u003c/b\u003e\u003c/p\u003e\u003cp\u003eAfter evaluating research similar to the current study at the Children's Medical Center, the majority of the studies employed Pearson correlation to establish the relationship between particle concentration in hospital air and outdoor air \u003csup\u003e\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e, \u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e\u003c/sup\u003e. Pearson correlation applies when the data has a normal distribution. In this study at Children's Medical Center, we used Spearman correlation to assess the non-normality of the acquired data.\u003c/p\u003e\u003cp\u003eAccording to the Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e11\u003c/span\u003e, the more we move from lighter shades of purple to darker ones, the correlation increases. In this chart, the correlation between concentration and the number of particles in indoor air and outdoor air has been examined. The correlation between concentration and particle count in indoor air is close to one. The correlation between concentration and particle count in outdoor air is also close to one. The correlation values between the PM\u003csub\u003e1\u003c/sub\u003e, PM\u003csub\u003e2.5\u003c/sub\u003e, and PM\u003csub\u003e10\u003c/sub\u003e concentrations in indoor and outdoor air are 0.61, 0.59, and 0.59, respectively. A higher numerical value of correlation indicates that as the concentration of suspended particles in the outdoor air increases, their concentration in the indoor air also increases.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e"},{"header":"4. Limitations of the study and potential future perspectives","content":"\u003cp\u003eThis study does not consider daily, seasonal, and annual variations in pollutants, as well as hourly air exchange, and these measurements were conducted only over a limited time. The study was conducted cross-sectionally, and the long-term impact of air quality improvement measures has not been examined. The relationship between air quality and health outcomes for patients and staff has not been directly measured. In future studies, it is suggested to calculate the air changes per hour in different situations regarding the on and off states of the mechanical ventilation system and the opening or closing of windows. Additionally, more precise methods can be used in future studies, such as measuring the reduction of carbon dioxide concentration over time and then calculating the air changes per hour.\u003c/p\u003e"},{"header":"5. Conclusion","content":"\u003cp\u003eThe present study at the Children's Medical Center examined the impact of various environmental factors, including ventilation systems, temperature, humidity, number of people present, and types of activities, on the indoor air quality of the hospital. The results indicated that the average ACH in the warm season was higher than in the cold season. The increase in the air change rate per hour in the warm season may be related to the greater use of the natural ventilation system. Additionally, the number of colonies counted after 24 hours in the warm season has increased compared to the cold season. Since the temperature and humidity in the warm season are higher than in the cold season, it can lead to increased bacterial growth. The mechanical ventilation system with HEPA filters (in the linkage section) was highly effective in reducing suspended particles. The average PM\u003csub\u003e2.5\u003c/sub\u003e, PM\u003csub\u003e10\u003c/sub\u003e, and PM\u003csub\u003e1\u003c/sub\u003e concentration in the Children's Medical Center during the cold season (November to December) is higher than in the warm season (April to August). In the cold season, outdoor air pollution caused by phenomena such as temperature inversion and combustion activities (like fossil fuels) increases. This pollution may enter indoor air through ventilation systems and contribute to the increase in particle concentration in the indoor environment. Temperature inversion, as well as an increase in particle concentration and quantity, occur often in Tehran throughout the late fall and winter months. The results of this study showed that in places with higher population density, such as the emergency department and inpatient rooms, the concentration of pollutants is higher and the air quality in these areas is not acceptable. Environmental elements and ventilation system performance have a direct impact on the hospital's air quality. Additionally, the correct utilization and efficacy of these systems are compromised due to the fact that the patients in each sector are responsible for adjusting the ventilation system settings. Patients, on the other hand, do not feel comfortable or at peace with the room temperature when ventilation systems are turned on during the cold season, so they turn them off. Using effective ventilation systems and limiting the number of people in the wards can greatly improve air quality and create a safer environment for patients and staff.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003ch2\u003eCompeting interests\u003c/h2\u003e\u003cp\u003eThe authors declare no competing interests.\u003c/p\u003e\u003c/p\u003e\u003ch2\u003eFunding\u003c/h2\u003e\u003cp\u003eThe budget of this project has been provided by Center for Air Pollution Research (CAPR), Institute for Environmental Research (IER), Tehran University of Medical Sciences (Grant number: \u003cspan type=\"Underline\" class=\"Underline\" name=\"Emphasis\"\u003e1403-3-110-74055\u003c/span\u003e).\u003c/p\u003e\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eN.D., M.S.H., A.S., M.T.M., S.J., and K.N. contributed to the conception and design of the study. N.D. and M.S.H. performed the experiments and collected data. A.S. and M.T.M. conducted data analysis and interpretation. S.J. assisted with methodology and validation. K.N. supervised the project and secured funding. N.D. and M.S.H. wrote the initial manuscript draft. All authors reviewed, edited, and approved the final manuscript.\u003c/p\u003e\u003ch2\u003eAcknowledgement\u003c/h2\u003e\u003cp\u003eThe authors would like to acknowledge the Children's Medical Center, Tehran University of Medical Sciences for their collaborations. I would like to sincerely thank the managers and all the staff of the Children's Medical Center for their good cooperation. This research was financially supported by Center for Air Pollution Research (CAPR), Institute for Environmental Research (IER), Tehran University of Medical Sciences (Grant number: 1403-3-110-74055).\u003c/p\u003e\u003ch2\u003eData Availability\u003c/h2\u003e\u003cp\u003eThe file associated with the retrieved articles for this study is available through the corresponding author for a suitable reason.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003ePlazas, F. L. \u0026amp; de Tejada, C. S. Natural ventilation to improve indoor air quality (IAQ) in existing homes: The development of health-based and context-specific user guidelines. \u003cem\u003eEnergy Build.\u003c/em\u003e \u003cb\u003e314\u003c/b\u003e, 114248 (2024).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eJones, A. P. Indoor air quality and health. \u003cem\u003eAtmos. 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Med.\u003c/em\u003e \u003cb\u003e21\u003c/b\u003e (1), 39 (2014).\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Indoor air quality, Hospital, ACH, Ventilation, PM","lastPublishedDoi":"10.21203/rs.3.rs-7810595/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7810595/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eIn this study, number and concentrations \u0026nbsp;of PM\u003csub\u003e2.5\u003c/sub\u003e, PM\u003csub\u003e10\u003c/sub\u003e, and PM\u003csub\u003e1\u003c/sub\u003e in indoor and outdoor air, temperature, humidity, and CO\u003csub\u003e2\u003c/sub\u003e concentration, and air exchange per hour were examind in selected wards of the Children's Medical Center in Tehran city. To measure number and concentrations of indoor and outdoor particles and air velocity, the PLANTOWER PMS 5003 sensor and KIMO VT 115 (Hotwire thermo-anemometer) was used, respectively. Furthermore To measure temperature, humidity, and carbon dioxide concentration, the Testo 440 device was used. The average air exchange rate per hour in selected wards of the Children's Medical Center during the warm season (April to August) and the cold season (November to December) in 2024 was 24 and 12 times per hour, respectively. The average concentration of PM\u003csub\u003e2.5 \u003c/sub\u003eand PM\u003csub\u003e10\u003c/sub\u003e in the cold season (November to December) and the warm season (April to August) at the Children's Medical Center was 32 µg/m³ and 22 µg/m³ and 39 µg/m³ and 28 µg/m³, respectively. The average CO₂ concentration in the Children's Medical Center during the warm season was 270 ppm, which is lower compared to the cold season (390 ppm). Installing and upgrading mechanical ventilation systems using HEPA filters in all wards, especially sensitive areas like NICU, CICU, and operating rooms, can significantly impact the air quality within the wards.\u003c/p\u003e","manuscriptTitle":"An overview of ventilation and indoor air quality in selected wards of the Children's Medical Center","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-11-14 07:13:06","doi":"10.21203/rs.3.rs-7810595/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"0d089c40-6621-4d28-bc48-5a3605779e17","owner":[],"postedDate":"November 14th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[{"id":57935695,"name":"Earth and environmental sciences/Environmental sciences"},{"id":57935696,"name":"Health sciences/Health care"}],"tags":[],"updatedAt":"2025-12-17T06:38:49+00:00","versionOfRecord":[],"versionCreatedAt":"2025-11-14 07:13:06","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-7810595","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7810595","identity":"rs-7810595","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}