Abstract:
The Healthy Air, Healthy Schools Project began in 2020 to better understand the impact of
portable air cleaners as an intervention in schools to reduce particulate matter of outdoor origin
and improve clean air equity. Populations who experience ethnic/racial and social disparities
bear a disproportionate burden of air pollution exposure which should be considered when
planning and implementing air quality interventions in schools. The ongoing second phase of the
project is collecting real-time air quality and HEPA air cleaner usage data across 17 participating
schools in King County, Yakima County, and Yakama Nation that serve a diverse population
including Hispanic youth and BIPOC youth. This report is based on the six-month preliminary
results of 10 study schools in King County and builds on the short-term HEPA results from
Phase 1 of the study. One portable air cleaner with a HEPA (high efficiency particulate air) filter
was deployed in five classrooms at every study school. Air quality data, including PM2.5, was
recorded inside the same five classrooms and one outdoor location at each school to measure the
impact of HEPA air cleaners. HEPA energy usage was collected with an energy logger to
monitor whether the HEPAs were used and how much they were used. The average infiltration
rate of outdoor particulate matter from February to August 2023 was 71.5% across the schools
with observed school differences. Over the observation period, the HEPA air cleaners were used
56.1% of the deployment time, though between school differences were also observed. When on,
the HEPAs were 46.2% effective at reducing PM2.5 in classrooms when the outdoor PM2.5
concentration was greater than 12 μg/m3, the Environmental Project Agency’s annual threshold
for good air quality. As Phase 2 of the project continues, the study team will further analyze the
effectiveness and pattern of HEPA air purifier usage to inform recommendations on improving
air quality in schools.