Classroom air quality in a randomized crossover trial with portable HEPA air cleaners

Abstract

Children living in communities with lower socioeconomic status and higher minority populations are often disproportionately exposed to particulate matter (PM) compared to children living in other communities. We assessed whether adding HEPA filter air cleaners to classrooms with existing HVAC systems reduces indoor air pollution exposure. From July 2022 to June 2023, using a block randomized crossover trial of 17 Los Angeles Unified School District elementary schools, classroom PM concentrations were monitored and compared for 99 classrooms with HEPA filter air cleaners and 87 classrooms with non-HEPA filter air cleaners. In HEPA classrooms, average school-year PM2.5 was 39.9% lower (0.581 µg/m³; p < 0.001) and infiltration of outdoor PM2.5 into classrooms was 13.8–82.4% lower than non-HEPA classrooms, depending on the school.