​​​​​​​​Having good ventilation and air filtration in schools is very important to reduce COVID-19 and other respiratory diseases that spread through the air. Improving indoor air quality also creates a healthier school environment by limiting exposure to harmful chemicals and wildfire smoke (PDF). In addition, cleaner air quality can increase student performance and attendance. Improve indoor air quality by using one or more of the following strategies:

Optimize or Upgrade Your Mechanical Ventilation (HVAC) System

The HVAC system reduces hazards in the air by pulling in outdoor air and circulating indoor air through filters. Work with facility managers to optimize the HVAC system by reviewing the California Department of Public Health (CDPH) Guidance for Ventilation. Work with indoor air quality or ventilation consultants to assess whether the HVAC system needs an upgrade.

Open Doors and Windows (Natural Ventilation)

While natural ventilation can be an important tool to improve air quality, it is not as easy to control as mechanical ventilation. Opening windows and hallway doors on opposite sides of the room creates a cross draft which is the best way to naturally introduce outside air. Use carbon dioxide (CO2) monitors to determine if enough outdoor air is being brought into a classroom from natural or mechanical ventilation. Levels above 800 parts per million (ppm) CO2 can indicate more outdoor air is needed.

Add Portable Air Cleaning Devices (PACs)

Place portable air cleaning devices in classrooms (PDF) to supplement mechanical and natural ventilation. PACs are recommended to be used during wildfire smoke events when windows an​​d doors need to be closed and outdoor air quality is poor. Purchase PACs that are sized appropriately and circulate air through High Efficiency Particulate Air or “HEPA” filters. HEPA filters remove infectious particles by filtering them out of the air. Avoid devices that advertise ionizer, ozone, or other cleaning methods that add chemicals to the air. Alternatively, a low-cost DIY PAC can be built and added to classrooms as a temporary alternative but not for permanent use. ​

For more detailed information on improving indoor air quality, review the CDPH Guidance for Ventilation.​

Resources

• CDPH - Interim Guidance for Ventilation, Filtration, and Air Quality in Indoor Environments
• CDPH - Wildfire Smoke: Considerations for California’s Public Health Officials (PDF)
  
• CDPH - Tips for Portable Air Cleaners (Image)
• CDPH - Information for School Districts on Purchase of Filtration and Air Cleaning Devices (PDF)
• CDC - Are do-it-yourself DIY air cleaners effective at reducing the risk of COVID-19 transmission indoors?
• CDC - CO2 Monitors to Assess Ventilation
• EPA - Research on DIY Air Cleaners to Reduce Wildfire Smoke Indoors | US EPA
  
• UC Davis Corsi - Rosenthal Box DIY​​