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  • Writer's pictureJosh Veblen

Hold Your Breath. The Critical Need to Improve Indoor Air Quality in U.S. Schools

Updated: Jan 7

Nearly 57.5 million students, teachers, and staff enter U.S. classrooms every day. According to estimates from the Environmental Protection Agency, approximately 50% of those are exposed to air polluted with toxic chemicals, mold, viruses, bacteria, asbestos, pesticides, smog, exhaust fumes, and more.

The culprit? Indoor air pollution.

The EPA's Science Advisory Board (SAB) ranks indoor air pollution among the top five environmental risks to public health. Poor indoor air in schools frequently results from:

  • Improper HVAC installation and TAB (testing, adjusting, and balancing)

  • Deferred or inadequate maintenance on HVAC filters, belts, and drainage

  • Classroom occupancy changes

  • Nearby contaminated buildings or polluting facilities

  • Toxic construction materials, cleaning supplies, and pesticides

"Even before the COVID-19 pandemic, outdated and hazardous school buildings were undermining the quality of public education and putting students and educators at risk.”

Bobby Scott, Chairman of the House Education Committee

Neglecting indoor air quality problems can increase long- and short-term health effects for students and staff, such as:

  • Irritation of the eyes, nose, and throat

  • Headaches, dizziness, and fatigue

  • Respiratory diseases, heart disease, and cancer

Beyond the immediate health problems, poor indoor air quality has proven to:

  • Negatively impact student attendance, comfort, and performance

  • Reduce teacher and staff performance

  • Generate negative publicity for the district

  • Impact community trust

  • Create liability problems

How does improving air quality benefit schools?

The EPA asserts that “Good indoor air quality is shown to promote a pleasing learning and working environment, along with promoting a sense of welfare. A positive working and learning environment assists schools in providing the most efficient education for students.”

Specifically, improving indoor air quality in schools has proven to:

  • Improve test scores. A study of 100 U.S. schools found that measurable progress in math and reading scores were observed when indoor air quality was improved.

  • Improve student performance including addition skills, number comparison, reading, and comprehension

  • Reduce absenteeism due to respiratory diseases such as asthma. (Asthma is one of the leading causes of school absenteeism causing an estimated 13.8 million lost school days in children ages 5-17)

  • Protect occupants from outdoor air pollutants such as diesel fumes from busses, wildfires, and smog

What can be done?

Building engineers say that the most important air quality regimen is to make sure that air turns over frequently, is mixed with lots of fresh air, and that it passes through filters that remove viruses.

Ventilation systems for school buildings can vary, but most rely on the same basic principles. Here are a few recommendations for ensuring healthy air quality in classrooms.

1. Assess Current Equipment

Conduct a ventilation verification assessment of the existing HVAC system. This assessment should include a thorough examination of each piece of mechanical equipment to gauge total airflow, coil performance, demand control ventilation, filter installation, and CO2 monitoring. The results of the assessment will identify if any repairs, upgrades, or replacements are required.

2. Ensure Ventilation Rates Meet Industry Standards

Proper installation, operation, and maintenance of HVAC systems are key to proper ventilation in classrooms. Unfortunately, ventilation rates in classrooms routinely fall below minimum standardsand HVAC systems in many U.S. schools are failing.

A new report from the U.S. Government Accountability Office (GAO) shows that 54% of U.S. schools need to update or replace their ventilation systems. (This is up from 41% in their 2020 report.)

The American Society of Heating, Refrigeration, and Air Conditioning Engineers (ASHRAE) specifies a minimum ventilation rate for classrooms of 15 cubic feet per minute per person.

In California, the 2016 Building Energy Efficiency Standards (Title 24) have the same ventilation requirement for classrooms.

A recent study conducted by the UC Davis Energy and Efficiency Institute found that only 15% of California’s classrooms met the ventilation standard.

3. Upgrade and Replace Filters

Most airborne pathogens are microscopically small. The coronavirus particle is approximately 80 – 160 nanometers (about 500 times smaller than the width of a human hair). Such small virus particles stay airborne and can travel long distances carried by airflows in the extract air ducts of ventilation systems.

Most school buildings utilize a Minimum Efficiency Reporting Value (MERV) of 5 to 11 for filtration. ASHRAE recommends that schools should install a MERV 13 or better filtration wherever possible. If MERV 13 filters cannot be used without adversely impacting equipment, then the highest MERV-rated filter should be installed. HEPA filters are another option. Unfortunately, HEPA filters are very thick, require large amounts of energy, and since most large buildings weren’t designed for this type of equipment, they can be a challenge to install and expensive to operate. A possible workaround includes using stand-alone HEPA units in classrooms and other high-occupancy areas.

And finally, filters need to be replaced every 3 to 4 months during the school year to ensure sufficient airflow.

4. Increase Natural Ventilation if Possible

In addition to reducing energy consumption, natural ventilation provides higher air exchange rates and, in turn, a greater dilution factor.The Centers for Disease Control and Prevention recommends that schools should increase ventilation of outside air by opening windows and doors unless it creates concerns for students with asthma.

5. Control Humidity

We’ve known for years that damp conditions and mold increase the risk of respiratory issues by as much as 30% to 50%.

Since schools have such high occupancy levels (approximately four times as many occupants as office buildings with the same amount of floor space) vast amounts of outdoor air needs to be circulated throughout the building to ensure optimum ventilation. Even small amounts of moisture in outdoor air can lead to too much moisture indoors. This is especially prevalent during the spring, summer, and fall in states east of the Rocky Mountains.

Alternately, indoor air can become too dry in northern and mountain states during the heating season. While most schools are equipped with heating and cooling equipment to control indoor air temperatures, very few are designed with equipment dedicated to controlling moisture. As a result, indoor relative humidity in U.S. schools can range from less than 10% to over 90%.

Research suggests that keeping humidity between 40% to 60% may help to limit the spread of viruses within buildings while minimizing the risk of mold growth. The humidity in classrooms can be managed through the use of ventilation fans, repairing leaky pipes, and using a dehumidifier.

6. Optimize Temperature

In addition to ventilation, classroom temperature is proven to impact student performance. The U.S. Department of Education recommends that classroom temperatures should be maintained between 68 and 75 degrees Fahrenheit during the winter months, and between 73 degrees and 79 degrees Fahrenheit during the summer months.

A recent study discovered that:

  • Approximately 60% of classrooms were warmer than the recommended average maximum temperature

  • 30% of the teachers were dissatisfied or very dissatisfied with the temperature in their classroom

  • Approximately 10% of teachers said that the classroom temperature interfered “a lot with the learning environment"

7. Carefully Monitor CO2 Levels

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 400 ppm, indoor CO2 levels should be no more than 1,100 ppm.

There is extensive evidence that prolonged exposure to concentrated levels of CO2 is detrimental to a child’s ability to perform optimally in school. For example:

  • A Harvard study discovered that increasing indoor CO2 levels by 400 ppm results in a decrease in cognitive functioning by 21%.

  • Classrooms that are not properly ventilated may have CO2 levels as high as 3000 ppm. With CO2 levels that high, students could experience up to an 80% decrease in cognitive functions.

Monitoring carbon dioxide levels is an efficient way to monitor ventilation. CO2 sensors should be installed in classrooms to continually monitor the air quality. If there is an unexpected ventilation malfunction, the CO2 sensor will alert occupants.

Breathing Easier. U.S. Schools are Taking Action

New federal and state funding programs are helping school districts upgrade outdated HVAC systems and address a critical backlog of deferred maintenance, and much-needed infrastructure repairs, to improve indoor air quality in their schools.

The good news is that a recent report from the Center for Green Schools shows that schools in all 50 states are prioritizing indoor air quality over other facility upgrades. Key report findings include:

  • Nearly 50% of the school districts surveyed are committing funding to:

    • Upgrade or improve air filtration/HVAC

    • Repair systems to reduce the risk of illness

    • Replace windows, doors, and roofs and/or

    • Install UV lights for disease mitigation

  • Of all the funding categories tracked in the data set, air filtration/HVAC was the second-highest category for district-planned spending.

  • District interviewees noted that where HVAC upgrades were made in their schools, they were able to keep energy usage and costs to a minimum compared to schools with outdated systems.

And finally, the EPA is reporting that interest in the agency's 'Creating Healthy Indoor Air Quality in Schools' reference guide and tool kits has skyrocketed over the last year. "What we are seeing is this moment turning into a movement for improving indoor air quality in schools and creating healthier learning spaces,"

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Matthew Critchley
Matthew Critchley
4 days ago

Thanks to the HVAC Contractor Stuart company for recognizing the importance of indoor air quality and taking actionable steps to address it. Educating customers about the significance of clean air and offering personalized recommendations for their specific needs showcase a customer-centric approach to business.


Zak Crawley
Zak Crawley
Jan 15

Thank you for shedding light on the crucial need to improve indoor air quality. The information provided by the HVAC Repair Diamond Bar company is not only enlightening but also underscores the importance of investing in solutions that prioritize our well-being.

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