Key Findings: Portable HEPA cleaners reduced airborne virus concentrations by 37–60% and cut parental work absences due to child illness by 32% (5.53 vs 3.77 days; p=0.009).
Key Findings: 32% reduction in indoor PM₂.₅; 12.5% reduction in absenteeism (~1.3 fewer days per student per year). Largest effects in high-absence students.
Key Findings: Mean PM₂.₅ dropped from ~6 μg/m³ to ~1 μg/m³. Staff reported less coughing, allergies, and absenteeism.
Key Findings: Math scores rose +0.20 SD; English +0.18 SD.
Key Findings: PM₂.₅ lowered from ~40 → ~13 µg/m³; students scored significantly higher on English tests.
Key Findings: 0.21 SD increase in next-day cognitive index after nights with filtered air.
Key Findings: 45% reduction in PM₂.₅ exposure; FEV₁ improved 8.0%, PEF 16.5%; airway inflammation (exhaled NO) dropped 22.4%.
Key Findings: In poorly controlled cases, ACQ scores improved from 1.3 → 0.9 (p=0.003); quality-of-life improved (4.9 → 5.5, p=0.02).
Key Findings: Portable filtration reduced systolic BP by ~3.9 mmHg.
Key Findings: +12 min total sleep time; +19 min time in bed.
Key Findings: HEPA use may increase birth weight and child IQ at age 4.
Key Findings: Maternal purifier use linked to fewer low birth weight infants.
Key Findings: Mixed effects; some studies showed ≤60% reduction in transmission, others no effect.
Key Findings: Schools with better ventilation had 39% lower COVID incidence; ventilation + HEPA achieved 48% lower incidence.
Key Findings: Holidays cut transmission to children 20–29%, preventing 16–18% of seasonal flu cases.