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Indoor Air Quality at School

Children spend much of their youth inside the walls of a classroom — more than 15,000 total hours by high school graduation, to put it in perspective.1 Schools emphasize the importance of education, but what if we told you that the stuffy and polluted air could be the barrier to academic success?

41% of school districts need HVAC repairs and upgrades in at least half of their schools, which is equivalent to about 36,000 buildings nationwide.2 Schools with outdated HVAC systems and, therefore, poor ventilation and indoor air quality, are putting the health and performance of students and staff at risk. High levels of carbon dioxide (CO₂) and the spread of pathogens in classrooms can ultimately affect performance, concentration, physical health and well-being of occupants. It’s not a conversation about comfort, but rather the safety of children in our communities.

What’s in the air?

Common air contaminants in schools include:

Carbon Dioxide (CO₂)

An odorless and colorless gas. Human metabolic processes, like exhaling air, are common when a classroom is full, and outside air can contain CO₂ from the combustion of carbon fuels like those in cars and buses.


Exhaled air can contain bacteria and virus particles and without proper ventilation and humidity control, airborne pathogens can increase transmission of diseases, such as COVID-19 or the flu.

Volatile Organic Compounds (VOCs)

Building materials such as vinyl and other plastic surfaces, new glues, and even wallpapers can off-gas formaldehyde and other volatile organic compounds (VOCs) into the air.3

If classroom windows are left open, outdoor pollutants like pollen and fumes from school buses or cars can flow inside.

Carbon Dioxide in the Classroom

Significant amounts of CO₂ negatively impact the mind and body, and children are especially vulnerable as they’re still in early development stages. The highest concentration of CO₂ in classrooms derives from exhaled air4 when classrooms are full. The American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) recommends that CO₂ levels in classrooms be no more than 700 parts per million (ppm), and they set the maximum limit around 1,000 ppm.5 Any level above 2,000 ppm can result in physical symptoms like sleepiness, headaches, nausea and increased heart rate, and can alter cognitive abilities and attention span.

Consider the following:
  • 90% of schools do not meet the minimum ventilation standards.6

  • Asthma is triggered by exposure to indoor allergens, like dust, dirt and mold — commonly found in classrooms with poor ventilation. Asthma is one of the leading causes of missed school days and is connected to more than 10 million absences per year. Nearly 1 in 13 school-aged children are diagnosed with this chronic condition.7

  • There’s a 15% performance improvement when increased ventilation or lower CO₂ concentrations are present.8

  • Reducing CO₂ in classrooms from 2,100 ppm to 900 ppm can improve performance on tests and tasks by 12% in regard to speed and 2% in regard to accuracy.9

  • Lowering the CO₂ concentration from 4,200 ppm to 1,000 ppm would increase daily attendance by 2.5%, and reducing CO₂ from 2,400 ppm to 900 ppm would raise performance of national tests and school-leaving examinations by 5%.10

  • Dust mites thrive in homes with high humidity levels of 70% to 80% and can trigger symptoms for those with asthma and allergies.11

Schools are the foundation for our education system, but without adequate ventilation, they can be health hazards. School building owners and leadership need to take action to protect their students and staff long term, and turn an unhealthy environment into a safe haven for our kids.

How to Improve Ventilation in Schools

It doesn’t take a lot to improve the ventilation in your school. School building operators should hire a certified professional to conduct a Ventilation Verification. Through this non-invasive process, an HVAC professional will check filtration, ventilation rate, air distribution, CO₂ monitoring and more key functions for building health. From there, they will recommend any necessary repairs and upgrades to protect the health of occupants.

The Design Guidance for Education Facilities11, developed by ASHRAE Technical Committee 9.7, is a great tool for contractors and design professionals to sit down with school districts and discuss options to increase both energy efficiency and indoor air quality (IAQ).

Find an HVAC Professional

It takes a highly trained HVAC professional to conduct a Ventilation Verification, test and balance an HVAC system, or repair and replace it. If you care about the air you and your tenants breathe, your search for cleaner air starts here.