Essential Indoor Air Quality Tools for Reopening Schools

Essential Indoor Air Quality Tools for Reopening Schools

During the first half of 2020, the novel coronavirus pandemic radically changed how we live. Mandatory closures were implemented to slow the spread of the disease, but as we move into the second half of the year, we are beginning to see reopening plans put into effect, with mixed success.

In no space is reopening more controversial than schools, where close and prolonged proximity is inevitable. Many parents worry that their children will fall behind without in-person instruction, especially after these parents need to return to work. On the flip side, school environments are notorious breeding grounds for all kinds of illnesses, and COVID-19 is no expectation.


It is clear that, for schools that do decide to reopen to fully in-person or hybrid educational experiences, additional steps need to be taken to secure the health and safety of students, teachers, and staff. We have discussed some IAQ strategies for reopening already, but we wanted to address schools specifically, as schools face particular air quality issues that could impact COVID-19 transmission.

Indoor Air Quality Challenges for Schools

Solving indoor air quality issues in schools has been a long-standing issue, a result of several features unique to schools. Some of these challenges include:

  1. 1.Occupant density and proximity: Schools often have four times as many people occupying the same space when compared to office buildings.
  2. 2.Varied pollutant sources: indoor air pollutants in schools come from both outdoors and indoors, with different pollutants arising from science and art classes, gyms, home economics classes, industrial and vocational classes, and more.
  3. 3.Large HVAC systems: As school budgets are reduced, maintenance costs are often cut, and the large HVAC systems in schools may not receive proper maintenance and repair.
  4. 4.Unsuitable add-ons: As schools expand, they may add buildings that were not designed for the unique requirements of schools, and may not receive proper ventilation or maintenance.

The combination of the above circumstances makes it difficult to diagnose and solve IAQ issues, and some of these challenges will even carry over to the reopening process.

Indoor Air Quality Tools for Combating COVID-19 in Schools

For schools, there are four crucial IAQ tools to keep in mind: boosting ventilation, installing a proper air filtration system, maintaining healthy relative humidity levels, and implementing continuous air quality monitoring.


Even before the coronavirus pandemic, proper ventilation has been a stumbling block for many schools. Ventilation rates in schools often fall short of recommended ventilation rate minimums, and carbon dioxide levels, which serve as a proxy unit of ventilation, show a widespread failure to ventilate properly.

Ventilation, already a significant health issue because of its relationship with indoor air quality, is more important than ever in today’s pandemic. Recirculated air can carry coronavirus droplets, and possibly viral particles, that are introduced to the environment by infected individuals.

COVID-19 rendering cdc

There is increasing evidence that COVID-19 can transmit through aerosolized particles. 

Increasing the quantity of outdoor air used to ventilate schools will cut down on airborne and droplet transmissionRead more about this in our dedicated article., as the fresh air will not carry nearly as many droplets or particles. Likewise, monitoring carbon dioxide levels in schools will ensure that ventilation rates do not drop below optimal levels and will also enable students to learn at their best.

Air Filtration

Of course, if ambient air pollution levels are high, simply pumping in outdoor air isn’t the answer. Many schools use low-efficiency filters (MERV 1-4) to eliminate minimal levels of particulate matter, which may not be enough.

While the science isn’t clear whether enhanced air filtration systems will sufficiently capture the novel coronavirus, installing proper air filtration systems will at least protect students from exposure to airborne particulates produced outdoors and indoors. Any viral particles picked up by the filter will lower indoor concentrations, as an added benefit.

Relative Humidity

The third strategy we will discuss is optimizing relative humidity, which has to do with the transmission efficacy of the novel coronavirus. Viruses can spread more easily through dry air, and cilia, a hair-like organelle that helps protect our airways, do not function nearly as well in dry conditions.

Humid air isn’t the answer, however, as viruses like the novel coronavirus can remain viable for longer periods of time in humid air and on surfaces. It is crucial to strike a balance between dry and saturated, limiting both its spread and viability.

winter rockefeller plaza

Humidification is particularly needed during the wintertime, as relative humidity declines when cold air is heated. 

Current research supports a band of relative humidity, between 40% and 60%, where viral transmission is minimized, and occupant comfort is maximized. Keeping relative humidity in schools in this range, and monitoring it, will go a long way in combating COVID-19 in schools.

Continuous Air Quality Monitoring

Rounding off the list of indoor air quality tools for schools to use during reopening is continuous air quality monitoring.

First of all, air quality monitoring can be a big help to the three tools we’ve already discussed. By monitoring carbon dioxide levels, which are often used to measure ventilation, you can ensure that school interiors are introducing enough outdoor air into the ventilation system, thus preventing the spread of COVID-19 through recirculated air. Likewise, particulate matter readings can be used to assess the effectiveness of your air filtration system, and a relative humidity monitor is invaluable for maintaining optimal indoor relative humidity levels.

Additionally, air quality monitoring can provide further health benefits to students attending school in person. As schools reopening, cleaning efforts will be ramped up to render any SARS-CoV-2 viruses lingering on surfaces inert. While these cleaners and disinfectants are necessary, they can also release enormous quantities of volatile organic compounds into the indoor environment, which can be dangerous to students.

Keeping tabs on air quality parameters like particulate matter, TVOC, carbon dioxide, and relative humidity helps tie all of our IAQ strategies together, demonstrating to teachers and parents alike that schools will be as safe as possible during reopening.

This article was created by Dianna Smith.

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