Effectiveness of enhanced filtration interventions for improving indoor air quality in child-serving facilities

Indoor air quality (IAQ) in schools and other child-serving facilities is crucial for the health and development of children, a large and vulnerable population. Interventions to improve IAQ, e.g., enhancing HVAC system filtration and deploying portable air cleaners (PACs), are especially needed at facilities located in polluted areas. Evidence of the actual effectiveness of these interventions, however, is limited and the reported performance is inconsistent. The objectives of this study, a component of a larger community-based participatory research partnership, were to evaluate the effectiveness of, and factors influencing, interventions using enhanced filtration; compare standard school buildings with other child-serving facilities such as nurseries, community centers, and childcare houses; and to identify IAQ improvement challenges and suggest relatively low-cost and effective mitigation methods. We evaluated 33 spaces in 12 facilities that served children from daycare through high school ages. Week-long baseline and follow-up measurements and teacher/staff surveys were obtained before and after the filter interventions. In most facilities, thermal comfort was acceptable, but ventilation rates were low (air change rates from 0.9-1.4 h^-1). At baseline during school hours, indoor levels of PM_2.5 averaged 2.2-6.3 μg/m³ and indoor PM₁₀ averaged 5.7-26.9 μg/m³. Standard schools saw the highest particulate matter (PM) levels. The intervention reduced PM_2.5 and PM₁₀ concentrations in the standard schools and nursery (by 45 to 54% for PM_2.5), but had little effect at childcare houses. A linear mixed-effects model (LMM) indicated a ∼51% reduction of indoor PM_2.5 levels by the PACs. For standard school classrooms and the nursery, the effectiveness of filtration strategies could be predicted using single-zone mass balance models, but predictions were inconsistent for portable buildings, facilities containing very large rooms, and houses repurposed for childcare. Overall, enhanced filtration can improve IAQ in child-serving facilities, but the long-term effectiveness, energy and economic costs require consideration. We recommend that teachers and staff acquire appropriate training and education to support and sustain effective and cost-efficient IAQ improvements.