Improving Indoor Air Quality in California Schools2


Children spend a large portion of their day indoors at school. As a consequence, indoor air particles can build up including Carbon Dioxide and indoor pollutants such as volatile organic compounds and respiratory aerosols exhaled by building occupants, including COVID-19. Ensuring that schools are properly ventilated and have good indoor air quality is critical to protecting and supporting the health and well-being of students and teachers.


Research has found that increased ventilation rates, and especially mechanical ventilation are associated with increased student performance, improved respiratory health, increased student attendance, and lower risk of transmission of airborne infectious diseases. We recommend that school districts take the following actions to improve classroom ventilation and indoor air quality:
Step One: Test and adjust HVAC
Complete commissioning and acceptance testing of new HVAC systems as required by Title 24.
Run HVAC fans when classrooms are occupied to bring in fresh air.
Step Two: Operate ventilation fans continuously during school day
Step 3. Use filters with MERV 13+
Replace filters 2-3 times per school year.
Monitor classroom CO2 concentrations. Thermostats with CO2 sensors and stand-alone sensors are widely available.
Step 4. Install sensors in classrooms
Step 5: Test ventilation rates in HVAC systems
Test ventilation rates in existing HVAC systems and make corrections when needed.


Call and Write

Share this information with other teachers, officials, parents and facilities. Ask them to implement these steps to ensure better, safer air quality for everyone!
Take action - call and write
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Sign the Petition

Show your support in the establishment of a Ventilation and Energy Efficiency Verification/Repair Program that would prepare schools for reopening during the COVID-19 crisis.


News Coverage

  • Local School Districts Improving Air Filtration As More Campuses Allowed To Reopen (2021 | CBS Los Angeles)
  • Sac City schools paid $6 million for costly air cleaners with unnecessary features (2021 | Sacramento Bee)
  • Air circulation can fight coronavirus transmission — or help it spread. Here’s how to spot a faulty system. (2020 | Business Insider)
  • Do Air Filters in HVAC Systems Offer Protection Against Coronavirus Indoors? It Depends (2020 | DISCOVER Magazine)
  • Bad Air in California Schools: How Clean is the Air Your Kids are Breathing in Class? (2020 | KCRA)
  • Carbon Dioxide: The Invisible Indoor Air Pollutant in California’s Classrooms (2019 | NBC)
  • Many CA Classrooms Have Insufficient Ventilation According to New UC Davis Study (2019 | KQED)
  • How California schools’ HVAC systems are ‘silently undermining’ your child’s chance at success (2019 | The Sacramento Bee)


  • SASH Webinar – Improving Indoor Air Quality in Classrooms (2022 | Webinar)
  • How to Improve Indoor Air Quality when Reopening K-12 Schools (2020 | Watch Webinar|Download Slides|Q&As)
  • Dreaming the Future: How Zero Net Energy Design can Transform the School Environment (2018 | Webinar)


  • Modeling Impacts of Ventilation and Filtration Methods on Energy Use and Airborne Disease Transmission in Classrooms (2022 | Academic Journal Paper)
  • Characterizing the performance of a do-it-yourself (DIY) box fan air filter (2022 | Academic Journal Paper)
  • Understanding Teachers’ Experiences of Ventilation in California K-12 Classrooms and Implications for Supporting Safe Operation of Schools in the Wake of the COVID-19 Pandemic (2022 | Academic Journal Paper)
  • Testing Different Configurations of Do-It-Yourself Portable Air Cleaners (2021 | Case Study)
  • Considerations for Use and Selection of Portable Air Cleaners for Classrooms (2021 | White Paper)
  • Improving Ventilation and Indoor Environmental Quality in California Schools (2020 | Project Report)
  • Testing, Adjusting and Balancing HVAC Systems: An Overview of Certification Agencies (2020 | Technical Report)
  • Proposed Ventilation and Energy Efficiency Verification/Repair Program for School Reopening (2021 | White Paper)
  • Ventilation rates in California classrooms: Why many recent HVAC retrofits are not delivering sufficient ventilation (2019 | Academic Journal Article)

Additional Resources

Contact the Project Manager