By Dr. Marilyn Black
As K–12 schools plan to bring students and staff back for the fall term during the COVID-19 pandemic, administrators face unprecedented decisions focused on in-school health and safety. Reopening schools requires careful planning around classroom operations, public health measures, and building systems to reduce disease spread and protect students, teachers, and staff.
Across the United States, districts are adopting various models—fully remote learning, traditional in-person classes, or hybrid schedules where students alternate between classroom time and remote instruction. Each model presents different challenges for ensuring safe learning environments, but a common priority for all options is improving indoor air quality to reduce the potential for airborne transmission of SARS-CoV-2, the virus that causes COVID-19.
Emerging scientific evidence indicates that respiratory viruses can spread when infected people release aerosols while speaking, coughing, sneezing, or simply breathing. Small aerosol particles can remain suspended and travel farther than larger droplets, increasing the importance of ventilation and air cleaning in classrooms, offices, cafeterias, and other school spaces. For more technical background, see a technical brief by chemical and aerosol experts summarized by industry sources.
Although concern about airborne transmission has been amplified by the pandemic, good indoor air quality is always essential for health, learning, and comfort. Schools that focus on ventilation, filtration, humidity control, and safe cleaning practices will help reduce infection risk while supporting student concentration and staff well-being.
Consider the following practical strategies for improving indoor air quality and minimizing airborne exposure:
Put Proper Ventilation in Place
Professional organizations such as ASHRAE’s Epidemic Task Force have stated that adjustments to building operations—including heating, ventilation, and air-conditioning (HVAC) systems—can reduce airborne exposure to SARS-CoV-2. Schools should ensure HVAC systems are functioning as designed and maximize outdoor air intake to dilute any airborne virus particles. Increasing ventilation rates and prioritizing outdoor air exchange helps flush contaminants out of occupied spaces.
Where possible, minimize air recirculation by configuring systems to supply more fresh outdoor air. If recirculation is unavoidable, install the highest-efficiency filters compatible with the system—filters with higher MERV ratings capture more particles and reduce reintroduction of contaminants. Portable air cleaners equipped with true HEPA filtration can supplement central systems in classrooms, small offices, and workshops to reduce airborne particulates.
Maintain indoor relative humidity between about 40 and 60 percent, which supports respiratory health and occupant comfort, and promptly repair any water intrusion issues that could lead to mold or other indoor air quality problems.
Use Approved Disinfectants Only
Deep cleaning and disinfection are important elements of school reopening plans, but some disinfectant products contain volatile organic compounds (VOCs) that can harm respiratory health. Common ingredients such as alcohols, aldehydes, and glycols can evaporate into indoor air and cause short-term effects like eye and throat irritation, headaches, or nausea. With frequent or prolonged exposure, there may be risks to organs such as the liver or kidneys.
To reduce these hazards, school custodial teams should use only disinfectants and cleaning products approved for use against SARS-CoV-2 by the appropriate regulatory agency in the United States. Apply disinfectants in well-ventilated spaces, ideally where windows and doors can provide fresh air exchange during and after application. In areas with high VOC use, portable air cleaners that include activated carbon or other adsorption media may help reduce odor and VOC levels, though they will require more frequent filter maintenance under heavy chemical use.
Prioritize Indoor Air Quality During School Sessions
The upcoming school year is likely to look different from any before it. Still, by prioritizing indoor air quality—through improved ventilation, enhanced filtration, sensible humidity control, and prudent disinfectant use—schools can lower the risk of airborne disease transmission while supporting student performance and comfort. These measures, combined with established public health practices such as hand hygiene, mask use where appropriate, and physical distancing, create a layered approach that best protects occupants.
School leaders, facilities managers, and public health officials should communicate clearly with parents, staff, and students about the steps being taken to improve air quality and safety. Transparent plans and visible actions help build trust and ensure everyone understands how the school environment is being managed to protect health and learning.
About the author
Dr. Marilyn Black is vice president and senior technical advisor at Underwriters Laboratories, with expertise in indoor air quality, environmental health, and building systems.
This article was originally published by The Learning Counsel, a research institute and news media organization focused on the shift in education toward digital curriculum and learning models.