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

Abstract

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 between November 2020 and May 2021 in the homes of adults who tested positive for COVID-19. The intervention was air filtration with PAC operated with the HEPA filter set 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 PM_2.5 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. When a central air handler (CAH) was reported to be in use, filter-associated reductions of PM were statistically significant during the day (06:00-22:00) and night (22:01-05:59) in the primary rooms but only during the day in the secondary rooms. Our study adds to the literature evaluating the real-world effects of PACs on a secondary room and considering the impact of central air systems on PAC performance.

Keywords: Filtration effectiveness; Indoor air; Naturalistic study; Particulate matter; Portable air cleaner.

Fig. 1.

Flow diagram of the number of study participants.

Fig. 2.

Concentrations of PM_2.5 (Panel 1) and PM₁₀ (Panel 2) as stratified by room type, time period, and PAC state; mean PM concentrations noted with “X” marks; effectiveness values from Table 3 noted on the x-axis; * for p < 0.05, as per WSRT. Outliers: diamond (◇) for greater than Q3 + 3 IQRs or less than Q1 − 3 IQRs and circle (◯) for within Q3 + (1.5 to 3 IQRs) or within Q1 − (1.5 to 3 IQRs), where Q = quartile and IQR = interquartile range.

Fig. 3.

PAC effectiveness in reducing PM_2.5 (Panel 1) and PM₁₀ (Panel 2) in high-PM homes, as determined by paired approach and stratified by time period; mean PM concentrations noted with “X” marks.