Real-World Effectiveness of Portable Air Cleaners in Reducing Home Particulate Matter Concentrations

Portable air cleaners (PACs) equipped with HEPA filters are gaining attention as cost-effective means of decreasing indoor particulate matter (PM) air pollutants and airborne viruses. However, the performance of PACs in naturalistic settings and spaces beyond the room containing the PAC is not well characterized. We conducted a single-blinded randomized cross-over interventional study of the homes of adults who tested positive for COVID-19. The intervention was air filtration with PAC operated with the HEPA filter installed (“filter” condition) versus removed (“sham” condition, i.e., control). Sampling was performed in 29 homes for two consecutive 24-hour periods in the primary room (containing the PAC) and a secondary room. PAC effectiveness, calculated as reductions in overall mean PM2.5 and PM10 concentrations during the filter condition, were for the primary rooms 78.8% and 63.9% (n=23), respectively, and for the secondary rooms 57.9% and 60.4% (n=22), respectively. Use of a central air handler (CAH) was associated with enhanced and statistically significant reductions of PM in the primary rooms over the entire 24-hour period as well as during the day and night analyzed separately; a similar trend was observed in the secondary rooms, but it was significant during the day only. This is the first study to evaluate the effects of PACs on a secondary room and to consider the impact of central air systems on PAC performance.