Application of Short-Term Measurements to Estimate the Annual Mean Indoor Air Radon-222 Activity Concentration

In this work, a first trial of a method has been developed to estimate the average annual indoor radon activity concentration from three-week short-term measurements using active radon-222 measuring devices, considering relevant influencing parameters. 24 long-term measurements (6 months) and 50 short-term measurements (3 weeks) were carried out in 24 indoor spaces in private houses in four Austrian federal states between October 2022 and July 2023. At the same time as the short-term measurements, ambient parameters (outside and inside temperature, air pressure inside, outside, air humidity inside, outside, wind speed, wind direction, amount of precipitation) were also recorded to investigate their influence on the measured radon-222 activity concentrations. Building and usage data of the indoor spaces examined were also collected. Based on the evaluation of the radon-222 measurements carried out, a first guideline was developed for estimating the annual mean value of the radon-222 activity concentration from short-term measurements lasting around three weeks. Using further measurements and advanced physical-statistical methods, it would be possible to test, validate and improve the generalization of the method to indoor spaces and to further improve the functional relationships.