Finding F-1661

“RESULTS: 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.”

Simona Classroom air quality in a randomized crossover trial with portable HEPA air cleaners… (2025). J Expo Sci Environ Epidemiol. Page 1. CKB 1367

Structure

Factor: Particulate matter (PM₂.₅ and PM₁₀)
Intervention: Air filtration and air purifiers
Setting: classroom, US
Study design: block randomised crossover trial in elementary school classrooms: 99 classrooms with HEPA filter air cleaners compared with 87 classrooms with non-HEPA air cleaners over a school year, with classroom particle concentrations monitored throughout (class 2)
Effect: difference 39.9
Caveat: the absolute difference is small because the classroom concentrations themselves are low

A Finding records what one published document states, verbatim and with its page. It is not a conclusion of Coridum; see the Claims that build on it.