Air Quality in Schools: Why Monitoring Matters for Students and Staff

by Amanda Hawkins April 13, 2026

Modern school classroom with an air quality sensor on the windowsill

Last week, ninth-grader Rohan Seshan shared his interview with PurpleAir founder Adrian Dybwad right here on this blog. Rohan’s curiosity about air quality and environmental monitoring is exactly the kind of engagement that makes a difference, and it got us thinking about the places where students spend most of their time: school buildings.

The average American student spends about 1,000 hours per year inside a school. The quality of the air in those buildings affects everything from how well students concentrate in class to how many sick days they take. Yet indoor air quality in schools is often overlooked until a visible problem appears, like mold, a gas leak, or wildfire smoke outside.

What Makes School Air Quality Different

Schools face a unique combination of air quality challenges. Classrooms pack 20 to 30 people into a room for hours at a stretch, producing CO2 and generating particles from movement, supplies, and food. Many school buildings are decades old, with aging HVAC systems that struggle to keep up with ventilation demands. Art rooms, science labs, woodshops, and cafeterias each introduce their own mix of volatile organic compounds and particulate matter.

Budget constraints often mean that air filters are replaced on schedules driven by cost rather than performance, and portable air cleaners are rare outside of districts that have specifically invested in them. The result is that students and staff in many schools breathe air that would not meet the standards expected in a modern office building.

Outdoor air quality adds another layer. Schools located near highways, industrial areas, or agricultural operations are exposed to elevated levels of PM2.5, diesel particulates, or pesticides. During wildfire season, smoke can infiltrate buildings through open doors, windows, and ventilation intakes, raising indoor PM2.5 concentrations well above healthy levels.

Why It Matters for Learning

The connection between air quality and cognitive performance is well documented. A Harvard T.H. Chan School of Public Health study found that improved ventilation and lower pollutant concentrations led to significantly higher cognitive function scores in adults. The effects are even more pronounced for children, whose lungs are still developing and who breathe more air per pound of body weight than adults.

High CO2 levels, which accumulate quickly in poorly ventilated classrooms, are associated with drowsiness, reduced attention, and slower decision-making. Elevated PM2.5 has been linked to increased absences due to respiratory illness and asthma flare-ups. For the roughly 6 million children in the U.S. who have asthma, poor school air quality is not an abstract concern. It directly affects their ability to stay in the classroom.

How Monitoring Changes the Picture

The first step toward improving indoor air quality is knowing what’s actually in the air. Without data, decisions about ventilation, filtration, and building maintenance are based on assumptions or complaints rather than measurement.

Air quality sensors placed in classrooms, hallways, gyms, and cafeterias provide continuous visibility into conditions that would otherwise go unnoticed. When a sensor shows that PM2.5 is rising during a nearby wildfire, the school can close windows and turn on portable air cleaners before students start coughing. When CO2 readings spike in a packed classroom after lunch, it becomes clear that the ventilation system needs attention.

This data also helps schools make the case for funding. A semester of readings showing that certain rooms consistently exceed healthy air quality thresholds is far more persuasive in a budget meeting than a general request for “better air.”

What Schools Are Already Doing

Across the country, schools and districts are beginning to treat indoor air quality as a measurable, manageable priority:

Sensor networks in classrooms. Some districts have installed low-cost sensors in classrooms, giving teachers and administrators real-time visibility into PM2.5 and CO2 levels. When conditions deteriorate, teachers can adjust by moving activities outdoors, switching on air purifiers, or flagging rooms for HVAC review.
Wildfire smoke protocols. Schools in fire-prone regions are developing air quality action plans that specify when to cancel outdoor recess, when to turn on portable HEPA filters, and when to consider early dismissal. Real-time sensor data makes those decisions faster and more defensible.
Student-led monitoring projects. Programs that put sensors in students’ hands turn air quality into a hands-on STEM lesson. Students collect data, analyze patterns, compare indoor and outdoor readings, and present findings. The learning goes beyond science into civic engagement and environmental awareness.
Community partnerships. Schools that share their sensor data publicly, through platforms like the PurpleAir map, contribute to neighborhood-level air quality visibility. Parents, community members, and local officials can see conditions around schools alongside their own neighborhoods.

Getting Started

Improving air quality in a school does not require a full building renovation. Meaningful progress often starts with a few straightforward steps:

Measure first. Place air quality sensors in representative locations: a high-traffic classroom, the gym, the cafeteria, and near outdoor air intakes. Establish a baseline before making changes.
Address ventilation. Ensure HVAC systems are operating as designed. Increase outdoor air exchange rates where possible. In rooms with no mechanical ventilation, even opening windows on opposite sides of the room (cross-ventilation) makes a measurable difference.
Add filtration. Portable HEPA air cleaners in classrooms with high occupancy or poor ventilation reduce PM2.5 effectively. Corsi-Rosenthal boxes, made from box fans and MERV-13 filters, are a low-cost alternative that students can even build themselves.
Create a response plan. Define thresholds for action. What PM2.5 reading triggers a switch from outdoor to indoor recess? At what AQI level do portable cleaners get turned on? Written protocols remove guesswork.
Involve students. Air quality monitoring is a natural fit for science classes. Students who understand what they’re breathing tend to care about what they can do about it, as Rohan’s interview showed us.

The air inside a school building is not something most people think about, but it’s there every day, shaping how students feel, how they focus, and how often they get sick. Measuring it is the first step toward making it better.

PurpleAir Map · Air Quality Monitors · EPA Indoor Air Quality in Schools