Creating Healthy Indoor Air Quality in Classrooms |
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Creating Healthy Indoor Air Quality in Classrooms

creating healthy indoor air classrooms

The effects of poor indoor air quality in classrooms has been known for years. Chronic illnesses, reduced cognitive abilities, sleepiness, and increased absenteeism have all been attributed to poor IAQ.

What's more concerning today is the direct effects of CO2 levels regarding poor air quality and how it effects children in classrooms.

Why is Indoor Air Quality important in schools?

Many are aware that their health can be impacted through outdoor air pollution. But what about indoor air pollution? Studies by the U.S. Environmental Protection Agency (EPA) indicate that indoor level pollutants are actually 5x times higher than outdoor air levels. This is a problem since most of us spend a good deal of our day indoors - at home, in an office, or in a classroom.

Research also shows that indoor air pollution is one of the five major environmental risks to the the public health.

This is especially an issue for children in the classroom. Young lungs are particularly vulnerable to air pollution. When exposed, many children start to experience chronic respiratory problems, asthma, fatigue, lack of focus, and become more susceptible to airborne viruses.

    Common sense would tell us that dust, mold, mildew, and airborne viruses like COVID-19 are not good for health. But many do not realize the importance of monitoring indoor CO2 levels.

    • High carbon dioxide levels are an easy-to-measure indicator of overall indoor air quality since high CO2 levels correlate with high levels of dust, mold, mildew and airborne viruses.
    • There is a correlation between high carbon dioxide levels and reduced attention and test scores.

    The American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) continues to be an invaluable resource in defining proper CO2 levels for commercial and residential buildings as well as schools, classrooms, and universities.

    Carbon Dioxide Levels in the Classroom

    This table shows different CO2 levels and their impact on human health. Note that while levels above 5,000ppm almost never occur, CO2 levels above 2,000ppm in closed classrooms are not uncommon.

    400ppm Normal outdoor air
    400-1,000ppm Typical CO2 levels found indoors
    1,000-2,000ppm  Common complaints of drowsiness or poor air quality
    2,000-5,000ppm Associated with headaches, fatigue, stagnant, stuffiness, poor concentration, loss of focus, increased heart rate, nausea
    > 5,000ppm Toxicity or oxygen deprivation may occur. This is the permissible exposure limit of the daily workplace exposure
    > 40,000ppm Immediately harmful due to oxygen deprivation


    The ASHRAE Standard 62-2001 “provide(s) indoor air quality standards that will be acceptable to human occupants and is intended to minimize the potential for adverse health effects.”

    Building codes in most states reference Standard 62, either in part or in its entirety, as part of their definition for minimum ventilation requirements.

    According to ASHRAE, the recommended CO2 level in buildings should be no more than 700 parts per million (ppm) above outdoor air. Since outdoor air is approximately 400ppm, indoor CO2 levels should be no more than 1,100 ppm.

    Note that this guideline is not designed to limit the amount of CO2, but rather to indicate that a proper level of clean air (15-20 CFM/person) is being distributed in indoor spaces like classrooms. And OSHA and the US Green Building Council have even tighter indoor CO2 recommendations.

    Following on the research already conducted on indoor air quality additional studies are now being formed like that at the University of Colorado focusing on how to control the transmission of airborne infectious diseases indoors, specifically in the classroom or university setting.

    Similar to to the CO2 research, the results demonstrate that once viruses are present in the classroom you have two choices:

    • Ventilate the building (bring fresh air in from outside) or 
    • Remove the virus from the air inside the building (filtration/HVAC systems)

    Currently, additional inspection criteria and standards are being developed, like that of the New York City Department of Health and Mental Hygiene. These standards are based on guidance by the CDC and WHO to ensure proper monitoring systems are in place in classrooms and group spaces to achieve sufficient ventilation. 

    The New York City standard states, "Proper air ventilation is key to stop the spread of airborne viruses."

    Per CDC guidance, it is highly recommended that schools:

    • Increase the amount of fresh air in classrooms 
    • Inspect, repair, and increase air filtration
    • Inspect and repair supply and exhaust fans
    • Deploy portable High-Efficiency Particulate Air (HEPA) filters
    • Install Indoor air quality monitoring devices
    • Ensure ventilation systems operate properly and provide acceptable indoor air quality for the current occupancy level for each space

    How common is poor IAQ and high CO2 levels?

    While exact figures are not known, according to the National Center for Education Statistics there are almost 99,000 public K-12 schools in America, and the average school building is at least 42 years old.

    Of these 30% reported heating systems, air conditioning systems, and ventilation/filtration systems to be in fair to poor condition.

    One of the reasons, is that many school buildings were built in the 1960s and 1970s to solve two problems: the increasing number of "baby boomer" children coming into the public school system, and the increasing cost of energy needed to heat or cool older school buildings.

    To solve these problems new schools built during those years used "modern" energy-saving features like windows that could not be opened. While "closing the envelope" reduced the cost to heat and cool the buildings, ironically, it resulted in sealed classrooms that trapped poor air quality, contaminants, and drove up CO2 levels past acceptable limits.

    Taking Action to Improve Air Quality in Schools

    Indoor Air Quality Monitors

    Pictured above: IAQMini CO2 Indoor Air Quality Monitor

    As more and more studies continue to show the negative effects of poor indoor air quality, not only does poor air circulation result in high levels of CO2 but also high levels of airborne illness.

    While studies have shown that high levels of carbon dioxide have reduced the amount of oxygen to the brain, studies have also shown that high levels of airborne illness tend to increase in rooms with poor levels of air circulation. Poor air circulation not only result in high levels of CO2 and viruses, but also high levels of dust, dander, germs, microbes, and other particles.

    The ideal indoor environment is one with (you guessed it) lots of outside, fresh air replacing the stale, contaminated air inside. In indoor environments such as classrooms, it is important that quality air quality monitors be placed to indicate should ventilation be required and further, eliminate potential pollutant exposure.

    Unfortunately, studies have shown that many universities, classrooms, and indoor learning centers do not have the proper ventilation rates to begin with. This has resulted in increases in child illness, lack of productivity, and uninterest in learning. Additionally, a review of referred archival journals commissioned by Berkeley Lab for their Scientific Findings Resource Bank concluded that:

    The available research provided “compelling evidence of an association of improved student performance with increased classroom ventilation rates.” Overall, eight out of 11 studies reported statistically significant improvements in at least some measures of student performance with increased ventilation rates or lower carbon dioxide concentrations, and a ninth study reported a statistically significant improvement in performance when applying a less stringent than typical criterion for statistical significance. Five of the studies were intervention studies that increased ventilation rates and measured changes in performance within students.
    Time-average carbon dioxide concentrations in classrooms, Berkeley Lab

    How to Improve Indoor Air Quality in Classrooms?

    The simplest solution is to talk to the building supervisor in your child’s school. Indoor air quality is normally monitored in all school buildings, and the results are available to the public. Additionally, you can research online "indoor air quality in schools (your state)" or visit

    For educators and administrators looking for an indication of proper indoor air quality, indoor air quality monitors such as the RAD-0302: IAQMini CO2 Monitor can be used to properly monitor and measure carbon dioxide, temperature, and relative humidity.

    IAQ Mini CO2 Monitor

    By utilizing an indoor air quality monitor such as the RAD-0302, you can rest assure that should classroom levels exceed the normal threshold, the device will provide a prompt indication.

    Additional advantages of the IAQMini CO2 Monitor include:

    1. Advanced sensor technology (using NDIR sensing capabilities)
    2. Large LCD display for teachers, students, faculty for real-time levels
    3. Vibrant 3-color code display (Green/Yellow/Red) to indicate CO2 levels
    4. Easy to use, "plug-and-play" capabilities, monitors in minutes
    5. ECO saving power function darkens the LCD during periods of non-use

    Benefits of Air Quality Monitors in Classrooms

    When reflecting on what is happening across the world as we still continue to battle the pandemic, it is important to improve the quality and health of indoor air for our teachers, students, faculty, and staff members.

    When you implement air quality monitoring you can ensure safe operation in schools and maintain healthy facilities that include adequate ventilation, mitigate risk of virus exposure, and create healthier learning environments.

    Currently, the RAD-0302 continues to be used across universities, research facilities, and classrooms to provide monitoring and benefits such as:

    • Determining the risk of airborne viruses within individual classrooms
    • Monitoring classrooms simultaneously for ventilation indication
    • Creating a more productive and focused environment for students
    • Making parents feel confident in the air quality their children are breathing
    • Enabling a safer and healthier "back-to-school" program 

    For further information on monitoring indoor air quality, and ventilation best practices in your home, school, or office space, contact 


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