- • 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.