Particle removal efficiency of a household portable air cleaner in real-world residences: A single-blind cross-over field study.

• A single-blinded cross-over study was conducted in 20 urban residences in China. • Efficiencies of HEPA air cleaners at reducing indoor particles were evaluated. • Particle-reduction efficiency was ∼40% over 48 h under normal living conditions. • Particle-reduction efficiency had a significant association with the room volume. • Residences with large rooms should use multiple cleaners to achieve healthy air. Portable air cleaners are commonly used to reduce indoor air particles in China, but few studies have evaluated the treatment efficiency under real living conditions. We aimed to evaluate the efficiency of a portable air cleaner in common residences under normal living conditions. A single-blind cross-over field study was conducted in 20 urban residences in Chongqing, China. In each residence, one portable air cleaner was operated without a high-efficiency particulate air (HEPA) filter (sham filtration) for the first 48 h and with a HEPA filter (true filtration) for the next 48 h in the living room. Concentrations of PM 1.0 , PM 2.5 , respirable suspended particulate matter (RESP), PM 10 , and total suspended particulate matter (TSP) were measured simultaneously in indoor and ambient outdoor air. Compared to sham filtration, the average concentrations of indoor air particles were significantly lower when true filtration was used according to paired-sample t -tests (all p -values <0.05). However, indoor concentrations of PM 2.5 in 16 (80%) residences were still higher than the World Health Organization's (WHO) air quality guideline during true filtration. The removal efficiencies of the portable air cleaners with HEPA filters for these particles were about 40%. The removal efficiencies for PM 1.0 , PM 2.5 , and RESP had significant associations with the room volume, but not with the residence district, season, age of the building, floor level of the apartment, or ambient weather. Our results indicate that a portable air cleaner is effective in improving household air quality, but is not enough to ensure the air quality meeting WHO guideline in all real-world residences in polluted areas. [ABSTRACT FROM AUTHOR]