Healthy School Facilities: Indoor Air Quality

^{Redding School of the Arts, California Green Ribbon School}

The California Department of Education (CDE) recognizes indoor air quality (IAQ) as a major factor in indoor environmental quality and that IAQ can significantly affect academic achievement in schools and classrooms. To understand how IAQ affects student learning, it is necessary to examine how it affects student health.

When it comes to indoor learning environments, children have special needs, sensitivities, and vulnerabilities that uniquely affect their health.¹ Students’ lungs are still developing. They have narrower airways and they breathe larger volumes of air relative to their body size.² Providing good IAQ for learning environments includes knowledge that common indoor air contaminants can be concentrated at significantly higher levels than those found outdoors, particularly when ventilation rates are lower than recommended.³

The U.S. Environmental Protection Agency (EPA) points to findings in studies performed by the EPA and their Science Advisory Board that rank indoor air pollution among the top five environmental risks to public health.⁴

IAQ is Affected by the Following Elements:

1. Ventilation rate refers to the flow of outdoor air into the building and air recirculation within the building. One indicator of ventilation is the concentration level of Carbon Dioxide (CO₂), which is exhaled by building occupants. High CO₂ levels suggest that there is poor ventilation and movement of indoor air, which may lead to increased levels of various irritants. If there is not enough fresh air coming into the building, the combination of high CO₂ levels and stagnant air can make it difficult for building occupants to concentrate.
   
   
2. Humidity is an important element that can greatly affect IAQ. Humidity is the amount of water vapor in the air. High levels of humidity create the conditions where biological contaminants thrive. In addition, humidity rises with temperature because warm air can hold more moisture than cold air. Appropriate ventilation generally reduces indoor moisture levels. Ensuring proper ventilation, monitoring humidity levels, and preventing water intrusions into the building are important strategies for improving IAQ.⁵
   
   
3. Biological contaminants can include bacteria, viruses, mold, pollen and even droppings from rodents or pests. These may be small enough to be inhaled and may lead to illness. Without proper maintenance, ventilation and filtration, these biological contaminants may become concentrated in the air, affecting IAQ and human health.⁶
   
   
4. Chemical contaminants can come from art materials, cleaning products, building materials, science labs, auto and wood shops, air fresheners, perfumes, and other sources. These can affect occupants and especially those with asthma, compromised immune systems, and chemical sensitivities. Like biological contaminants, they can become more concentrated in the air with inadequate ventilation rates. The California Office of Environmental Health Hazard Assessment (OEHHA) outlines regulations with Guidelines for Purchasing and Safe Use of Art and Craft Materials for Schools.⁷ The California Healthy Schools Act defines requirements for cleaning products and Integrated Pest Management (IPM).⁸

Consistent attention to the four IAQ elements is vital. School facilities that provide adequate ventilation in all classrooms reduce student and teacher absenteeism and the transmission of infectious diseases while improving test scores and students’ academic performance.⁹

What Can Schools Do to Improve Indoor Air Quality?

Learn about IAQ

Learning about indoor air quality can help governing boards, district and school administrators, teachers, and staff understand the importance of IAQ. Free online training and staff development programs are available including comprehensive guidance from the EPA’s Tools for Schools Action Kit.¹⁰ The EPA also offers an on-demand IAQ Master Class Professional Training Webinar Series designed to assist school district staff in implementing an IAQ management program.¹¹ Clean Air in Schools is a self-guided, interactive introductory training course on school indoor air quality management offered by the U.S. Green Building Council.¹² In addition, the College of Engineering at the University of California, Davis and the California Department of Public Health (CDPH) created in-depth video lessons that can help teachers and school leaders manage and improve IAQ.¹³

District Policy

Governing boards can pass resolutions to design and build new construction and modernization projects with green building standards that promote IAQ. They can also establish policies to use programs and practices like EPA Tools for Schools that prioritize IAQ and proper maintenance of their current and proposed school facilities.¹⁴ School administrators can enforce policies to promote green cleaning products, eliminate air fresheners and perfumes in classrooms, and implement state regulations from organizations such as OEHHA. Local education agencies can consider the use of CO₂ monitors to help determine whether enough fresh air is being supplied to indoor learning environments.

School Facility Design

School and district administrators can encourage design professionals to specify less harmful building materials with low or no Volatile Organic Compounds (VOCs) and to avoid other indoor pollutants that can affect IAQ like radon, lead, asbestos, PCBs, pesticides, and more.¹⁵ Leaders can provide adequate ventilation and help to keep contaminants out of the building. Facility designs may include operable windows for fresh air, walk-off mats in the entrances, and locating parking areas away from building entrances. Providing adequate classroom storage also keeps clutter and dust to a minimum, important for maintaining good indoor air quality in learning spaces.

Maintenance and Operations

Regular replacement of heating, ventilation, and air conditioning (HVAC) filters help to keep contaminants out of classrooms. School leaders should carry out work orders received by teachers and staff to ensure that the buildings and grounds are properly maintained and to support healthy IAQ for students. Regular and adequate cleaning is essential. Using cleaning materials that do not emit VOCs and aggravate conditions like asthma are also an important component of a cleaning program. Maintenance staff should regularly test HVAC systems to ensure that there is adequate outdoor air intake and no obstructions in the ventilation systems.¹⁶

The evidence is clear - good indoor air quality, access to fresh air, and adequate ventilation rates improve student health, attendance, and academic performance.^17,18 District policies, school design choices, and effective operational practices are key to systemic improvements to indoor air quality in schools. When policies are successfully implemented and aligned with professional development, efforts to improve indoor air quality can enhance the safety, health, and success of all students.

Notes

1. Harvard T.H. Chan School of Public Health. 2018. Schools for Health: Foundations for Student Success (PDF). Harvard University.
   
   
2. See note 1.
   
   
3. American Society of Heating, Refrigeration, and Air-Conditioning Engineers (ASHRAE). 2022. Standard 62.1.b. Ventilation for Acceptable Indoor Air Quality .
   
   
4. U.S. Environmental Protection Agency. 2024. Why Indoor Air Quality is Important to Schools .
   
   
5. Seppänen, Olli and Jarek Kurnitski. 2009. Moisture control and ventilation: WHO Guidelines for Indoor Air Quality: Dampness and Mould . Geneva: World Health Organization.
   
   
6. U.S. Environmental Protection Agency. 2025. Reference Guide for Indoor Air Quality at Schools .
   
   
7. California Office of Environmental Health Hazard Assessment. 2019. Art Hazards. Guidelines for Purchasing and Safe Use of Art and Craft Materials for Schools .
   
   
8. California Department of Pesticide Regulation. 2024. California School Integrated Pest Management. The Healthy Schools Act Factsheet .
   
   
9. U.S. Environmental Protection Agency. 2012. Student Health and Academic Performance Quick Reference Guide (PDF).
   
   
10. U.S. Environmental Protection Agency. 2025. Indoor Air Quality Tools for Schools Action Kit .
    
    
11. U.S. Environmental Protection Agency. 2024. The Indoor Air Quality (IAQ) Master Class Professional Training Webinar Series .
    
    
12. United States Green Building Council (USGBC). 2025. Clean Air in Schools: Introductory Training Course on school indoor air quality management best practices . Center for Green Schools, U.S. Department of Energy, U.S. Environmental Protection Agency.
    
    
13. U.C. Davis and California Department of Public Health. October 2024. Indoor Air Quality Overview Videos and In-depth Lesson Videos .
    
    
14. U.S. Environmental Protection Agency. 2025. Indoor Air Quality Tools for Schools Preventative Maintenance Guidance Documents .
    
    
15. See note 14.
    
    
16. See note 14.
    
    
17. California Department of Education (CDE), Chronic Absenteeism and School Facilities: Research and Best Practices for Improving Student Attendance (PDF). Sacramento: California Department of Education, 2024.
    
    
18. American Lung Association. 2025. Clean Air at School: Resources to protect indoor air at school .