Studying the efficiency of air cleaners at removing various indoor air impurities in classrooms and the relation to pupils’ symptoms

The existing knowledge on the effect of air cleaners in reducing different indoor impurities and health symptoms real-life applications is still insufficient. PUHHO study aimed to fill this gap with a blinded intervention 18 primary school classrooms. was conducted during 8 weeks 2 without cleaner, 3 cleaner full operation (filtration) moderate airflow (200 - 400 m /h) sham (air blowing filtration). latter two interventions were mixed setup. Small, but statistically non-significant reductions particulate matter levels (PM2.5; diameter less than 2.5 µm PM10; particles 10 µm) observed when comparing filtration recirculation alone (sham operation). use had no significant level total volatile organic compounds (TVOC). Air did not have microbial or microbiome Filtration by found significantly reduce upper (4.0%) lower airway (2.5%) other symptoms, nearly equivalent alone.