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. 2022 Sep 13;19(18):11517.
doi: 10.3390/ijerph191811517.

Efficacy of HEPA Air Cleaner on Improving Indoor Particulate Matter 2.5 Concentration

Chiu-Fan Chen  1 , Chun-Hsiang Hsu  1 , Yu-Jung Chang  2 , Chao-Hsien Lee  3 , David Lin Lee  1   4
Affiliations

Efficacy of HEPA Air Cleaner on Improving Indoor Particulate Matter 2.5 Concentration

Chiu-Fan Chen et al. Int J Environ Res Public Health. .

Abstract

High-efficiency particulate air (HEPA) filters is a potential tool used to remove fine particles and improve indoor air quality. This study aims to analyze the real-world efficacy of portable HEPA air cleaners in a household environment. Laser light dispersion PM2.5 sensors are used to continuously monitor the indoor and outdoor PM2.5 level before and after HEPA air cleaner filtration. Overall, HEPA air cleaners significantly reduce the indoor PM2.5 level (33.5 ± 10.3 vs. 17.2 ± 10.7 µg/m3, mean difference (MD) = -16.3 µg/m3, p < 0.001) and indoor/outdoor PM2.5% (76.3 ± 16.8 vs. 38.6 ± 19.8%, MD = -37.7%, p < 0.001). The efficacy to reduce PM2.5 is strongest in three machines with medium-flow setting group (indoor PM2.5 MD: -26.5 µg/m3, indoor/outdoor PM2.5 percentage MD: -56.4%). Multiple linear regression demonstrates that outdoor PM2.5, machine number, airflow speed, and window ventilation are significant factors associated with indoor PM2.5 concentrations (R = 0.879) and percentage of the indoor/outdoor PM2.5 ratio (R = 0.808). HEPA air cleaners can effectively improve indoor PM2.5 air pollution. Adequate air cleaner machine numbers, appropriate airflow, and window ventilation limitations are important to achieve the best efficacy of the HEPA air cleaner.

Keywords: HEPA; PM2.5; air cleaner; air pollution.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Flow chart of air cleaner study. For each experiment (24 h each time, totaling 3 times in each group), in the first 12 h the air cleaner is turned off. Then in the following 12 h, the air cleaner is turned on to evaluate the efficacy of indoor PM2.5 removal.
Figure 2
Figure 2
Overall changes in indoor and outdoor PM2.5 levels before and after air cleaner use: (A) outdoor PM2.5; (B) indoor PM2.5; and (C) indoor/outdoor PM2.5 percentage. * outliers.
Figure 3
Figure 3
Details of the changes in indoor/outdoor PM2.5 percentage of each study group before and after air cleaner use. Remarkable improvements of indoor/outdoor PM2.5 percentage are noted after air cleaner use, except for the 1 machine low flow group. * outliers.
Figure 4
Figure 4
Box plots of PM2.5 outcomes in the six groups: (A) indoor/outdoor PM2.5 percentage and (B) indoor PM2.5 levels. More air cleaner machines and higher flow speeds are significantly associated with better indoor PM2.5 level. * outliers.
Figure 5
Figure 5
Details on the influence of living room window ventilation on the efficacy of air cleaners in each study group. The efficacy of HEPA filter air cleaner is severely impaired during period of window open for ventilation. * outliers.
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