How to Improve Indoor Air Quality in Schools

5 Key Indoor Air Quality Issues in Schools and Ways to Address Them

Improving indoor air quality (IAQ) is top of mind for schools as they continue their efforts to protect students, teachers and staff from Covid-19. However, did you know that the benefits of IAQ extend far beyond Covid-19? This article explores why schools should prioritize their IAQ, the negative consequences of poor IAQ, and the importance of clean air for student health and performance. We identify five key IAQ issues many schools face and provide four ways to address them.


Air Pollution Isn’t Just an Outdoor Problem

When we think about air pollution, we usually imagine the outdoor environment. However, the concentration of air pollutants can in fact be several times higher indoors compared to outside. Various factors in school settings – such as students spending long periods of time in close proximity to each other, the presence of pollutants from different activities throughout different school spaces, and limited budgets and resources to address indoor air quality issues, to name a few – create a unique environment for managing indoor air quality.


Importance of IAQ

Clean air is essential to our health. Air pollutants can contribute to a range of short-term symptoms, such as eye, nose and throat irritation and headaches, as well as long-term adverse health outcomes, such as diabetes, cardiovascular disease, lung cancer and respiratory issues. They can even play a role in premature mortality: air pollution is considered one of the greatest killers of our generation. Children are especially vulnerable to air pollution’s adverse effects due to their developing bodies and behaviors.

Healthy Air, Healthy Minds

Air quality isn’t just important for physical health. Growing evidence suggests that exposure to air pollution negatively affects children’s neurodevelopment. Research has also linked better air quality to higher productivity and better performance among students, such as improved concentration and test scores.


Air Quality Concerns in Schools

An estimated 41% of school districts need to update or replace heating, ventilation, and air conditioning (HVAC) systems in at least half of their schools, representing about 36,000 public schools (grades K-12) nationwide that need HVAC updates. According to the last School Health Policies and Practices Study (SHPPS) conducted by the CDC, only 48.9% schools reported implementation of indoor air quality management programs in 2016.

However, in response to the Covid-19 pandemic, many schools across the nation are now prioritizing IAQ and ventilation. The Center for Green Schools recently published a report detailing indoor air quality measures schools have implemented in response to the pandemic. The study found that among the 47 school districts and independent schools surveyed, 87% increased outdoor air supply through existing HVAC systems, 77% imposed a pre/post-occupancy flushing strategy and 70% upgraded their filters in at least some of their schools.


5 Common IAQ Issues in Schools

1. Infiltration of Ambient Air Pollution

IAQ is significantly influenced by outdoor air quality, due to the infiltration of air from the outside. Once inside, pollutants can accumulate, and research shows that the concentration of toxins, allergens and other pollutants can be up to five times higher indoors than it is outside. Outdoor air pollution can negatively influence students’ attendance and performance. For example, one study of public schools in Michigan found that schools located in areas with the highest air pollution levels had the lowest attendance rates and the highest proportion of students failing to meet state educational testing standards.

2. Allergens & Asthma Triggers

Indoor environmental exposures to substances such as pollen, dust mites and pests – which are commonly present in schools – can cause allergic reactions in many people. Common symptoms of allergic reactions are similar to those of a cold, including a runny nose and congestion, sneezing, and watery eyes. Asthma often accompanies allergies, and asthma symptoms in the lungs and airways can be triggered by the same allergens.

Seasonal pollen allergies are linked to poorer cognitive performance, which can affect educational outcomes. In fact, researchers have found that students score worse on tests when pollen counts are high or when they are experiencing allergy symptoms.

3. Dampness and Mold

Building dampness and mold in schools have been associated with increased respiratory health symptoms such as coughing, wheezing and allergic rhinitis; greater prevalence of asthma; and respiratory-related absenteeism. A study of over 1,000 school children found that the concentration of mold found in floor dust was associated with headache, dizziness, and concentration problems.

In the U.S., allergic rhinitis causes about two million – and asthma about seven million – lost school days per year among children and adolescents. In fact, asthma is the leading cause of school absenteeism in the U.S. due to chronic illness.

4. High Levels of Carbon Dioxide (CO2)

CO2 levels are a good indicator of how much fresh air there is in an indoor space; the higher the levels of CO2, the less fresh air there is. Without fresh air, it is harder for indoor pollutants to disperse, and their levels can build up. CO2 can also have a direct negative impact on cognitive performance; elevated levels of CO2 have been associated with increased student absence and symptoms of sick building syndrome, as well as wheezing among children attending daycare.

In classrooms, higher CO2 levels have also been linked to poorer concentration and cognitive performance, among other indicators of poor academic performance. A study conducted among students aged 10-11 found that increased levels of CO2 (from a mean of 690 ppm to a mean of 2,909 ppm) led to a decrease in “power of attention” of approximately 5%, which is similar to the impact a student might feel from skipping breakfast.

The American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) recommends that indoor CO2 concentrations be maintained below 1,000 parts per million. However, studies of CO2 levels in classrooms find that they often exceed recommended maximums. A 2017 review found that the average and median peak values of CO2 in schools across the world, in the time periods studied, were always over 1,000 ppm, and often over 2,000 ppm, while maximum peak values ranged from about 3,000 to 6,000 ppm.

5. Radon

Radon is a colorless, odorless, radioactive gas that is released from the breakdown of radioactive elements in rocks and soil, and can seep into buildings from cracks in floors, construction joints, and/or around service pipes. According to EPA estimates, radon is the number one cause of lung cancer among non-smokers, and is the second leading cause of lung cancer in the U.S. (after smoking), leading to 21,000 deaths a year.

Studies have shown that the risk of lung cancer due to exposure to radon in children may be up to three times higher compared to adults, due to differences in lung shape and size. The EPA estimates that 70,000+ schoolrooms in use today have high short-term radon levels.


How to Improve Indoor Air Quality in Schools

1. Ventilation

Ventilation systems can play an important role in diluting pollutant concentrations that have built up indoors by bringing in fresh air from the outdoors. Studies of schoolchildren suggest that increasing the outdoor air supply can meaningfully improve their academic performance at relatively low energy and capital costs. One experiment found that doubling the outdoor air supply rate to classrooms improved the speed of schoolwork performance by about 8%.

Increase ventilation by opening windows (using caution when outdoor air quality is poor) or disabling demand-controlled ventilation (DCV) controls that reduce air supply based on occupancy or temperature.

2. Purification

Air purifiers can help reduce the concentration of pollutants indoors by actively filtering indoor air. One study found that using four portable air purifiers in a school classroom reduced the concentration of aerosols by over 90% within a 30 minute period (with an air exchange rate 5.5 h−1), compared with a neighboring classroom without air purifiers.

Install portable air purifiers throughout the school (e.g., classrooms, cafeteria, nurses offices) for cleaner air. Delos Compact air purification units, for example, have patented technology that utilizes electrostatic precipitation combined with mechanical filtration to capture and deactivate bacteria and viruses, as well as trap particulate matter (PM2.5 and PM10). This technology is capable of capturing ultrafine particles as small as 0.007 microns at 99.99% efficiency.* To-date, Delos has provided over 150,000 Delos Compact air purification units to schools across the country.

3. Indoor Air Quality Monitoring

Indoor air quality monitors can track the levels of several types of air pollutants (e.g., PM2.5, PM10, TVOCs) and other air quality parameters (CO2, temperature, humidity) across the school. Depending on the IAQ issues identified, schools can work to determine what IAQ remediation efforts are needed to optimize their air quality. Many consumer-grade, easy-to-use monitors are available online.

4. Outdoor Air Quality Monitoring

Because outdoor air pollutants can easily get inside (e.g., through open windows and doors and/or cracks in walls, doors and window sealants), it is important to stay informed about local ambient air quality. Check resources like AirNow or Breezometer for real-time outdoor air quality information. If the outdoor air quality is poor, keep all classroom windows closed, and close the fresh-air intake of the AC unit (if applicable). That way, on days when outdoor air quality is poor, school buildings can offer better quality air inside (particularly if air purification is also utilized).


Delos IAQ School Solutions

Improving IAQ not only helps to protect students and staff from airborne diseases, such as Covid-19 and the flu, but can also improve student productivity and performance. The solutions provided in this article highlight actionable measures schools can take to remediate common IAQ issues. Cleaner air in schools can help to create learning environments where students and teachers alike can thrive.

For more information on indoor environmental factors that affect student health, well-being and performance, and steps that schools can take to address these factors, make sure to check out our white paper, Healthy Learning Environments. To explore our air purifiers, check out the Delos Shop and contact us to learn more about why our clean air technology is trusted by some of the largest school districts in the U.S., including the NYC Department of Education, Chicago, Miami-Dade County, Boston, Baltimore, and Portland Public Schools.


Edited by: Radhika Singh


* Individual particle sizes and specific particle ranges may have different filtration efficiency rates. SARS-CoV-2, the virus that causes Covid-19, ranges in size from 0.06-0.14 microns.