The Path Forward
Moving the needle on student achievement is notoriously difficult. Most educational interventions show modest effects despite substantial costs. Clean air represents a rare exception—a simple, affordable intervention with large, measurable benefits for learning, health, and equity.
The evidence supporting classroom air quality improvements is robust and growing. What's needed now is implementation at scale:
School Leaders
Can pilot air purifiers in high-need classrooms and expand based on results
Policymakers
Can establish indoor air quality standards and funding mechanisms
Communities
Can advocate for healthy learning environments as a basic educational right
Effective Solutions
Many schools think you need to do expensive HVAC upgrades. What people don't realize is that adding air purifiers to classrooms, especially in old schools with poor ventilation, is one of the most effective interventions available. You generally can't get enough equivalent air changes per hour (eACH) without them. And it's extremely affordable.
Portable Air Purifiers
Portable air purifiers represent the most cost-effective solution. At $500-1,000 per classroom with <$100 annual operating costs, they deliver cognitive and health benefits that would cost thousands through other educational interventions. Installation requires no special training—plug in, turn on, change filters annually.
The Case for Your District
- Minimal burden: Just plug in and change filters annually
- Maximum impact: Benefits all students, especially those near pollution sources
- Proven results: Growing evidence base across multiple countries
- Cost-effective: Few dollars per student yearly vs. expensive HVAC upgrades
Ventilation Improvements
Ventilation improvements provide additional longer-term solutions. Studies show direct correlations between ventilation rates and academic achievement, with measurable progress in math and reading when schools improve air exchange rates. However, they don't replace adding air purifiers.
Air Quality Monitoring
Air quality monitoring makes the invisible visible. Real-time CO₂ and particulate matter sensors help schools identify problems and verify solutions are working.
1. Choose Appropriate Air Cleaners
- Prioritize clean-air delivery rate (CADR): Choose units whose combined CADR meets or exceeds your calculated requirement, usually at least 750 CFM total per classroom. Multiple smaller units can be quieter and easier to place than a single large one.
- MERV 13–16 or HEPA filters: MERV 13 filters strike a good balance between particle removal and airflow. DIY Corsi-Rosenthal boxes using four or five MERV 13 filters deliver 300–400 cfm at low cost. Commercial HEPA purifiers provide high efficiency but often less airflow and cost more.
- Check noise ratings: Select products that operate below 50 decibels at the speed needed to meet CADR requirements. Students and teachers should be able to converse comfortably.
- Safety features: Ensure fans have fused plugs and guard grills. For DIY boxes, secure filters with tape or bungee cords and add a cardboard or 3D-printed shroud to improve performance.
2. Installation & Operation
- Placement: Position air cleaners centrally in the room away from walls, draperies and tall furniture. Leave at least 6–12 inches of clearance around the intake and exhaust. Avoid pointing the outlet directly at students.
- Number of units: Distribute multiple purifiers evenly to avoid dead zones. For long or oddly shaped rooms, place units at opposite ends. Avoid blocking both sides of box fans or placing heavy objects on top.
- Fan speed: Run purifiers continuously during occupancy on the highest comfortable speed. Note that teachers often turn units down if they're too loud, but this significantly reduces clean-air delivery rate—select quieter units to ensure they stay on high.
3. Maintenance & Filter Replacement
- Replace filters annually: Replace filters at least once a year.
- Retire aged equipment: Replace box fans after roughly five years of service. Always use units with modern safety features, including thermal fuses and tip-over protection.
Ready to improve air quality in your school?
Apply for our Spring 2026 Grant Cohort and get expert support for your district.