Air Quality in Schools

Kids spend roughly 1,000 hours a year in classrooms. Their lungs are still developing, they breathe more air per pound of body weight than adults, and they cannot control the building they sit in. Classroom air quality matters more than most parents and administrators realize, and it sits at the intersection of HVAC engineering, building age, location, and budget.

What's in classroom air

A typical classroom mix:

• Carbon dioxide (CO2) from breathing. Not toxic at typical indoor levels, but a proxy for how well the room is ventilated. Outdoor CO2 is around 420 ppm; classrooms regularly exceed 1,500 ppm and sometimes 3,000.
• PM2.5 infiltrating from outdoors, plus indoor sources (printers, art supplies, food prep).
• Volatile organic compounds (VOCs) from cleaning products, markers, glues, carpets, and furnishings.
• Mold spores in humid or water-damaged buildings.
• Allergens (dust mite, cockroach, mouse) in older buildings.
• Outdoor pollutants that intrude: ozone in summer, NO2 and PM from nearby traffic, smoke during fire season.

Ventilation and CO2

ASHRAE Standard 62.1 recommends at least 5 liters per second per person of outdoor air in classrooms, with an indoor CO2 target around 1,100 ppm (700 ppm above outdoor levels). California's Department of Public Health recommends staying below 800 ppm. Many real classrooms exceed both.

Why this matters beyond stale air:

• Studies show measurable cognitive decline above 1,000 ppm CO2 and 15 to 50 percent declines in some decision-making tasks at 1,500 ppm.
• Doubling outdoor air supply from 5 to 10 L/s per person cuts classroom CO2 roughly in half and shows up in test performance.
• High CO2 correlates with absenteeism in several large studies.

A low-cost CO2 monitor in each classroom is one of the highest-value interventions a school can make. It turns ventilation from invisible to obvious.

Local factors

• Building age. Pre-1978 buildings carry lead paint risk. Pre-1980s often have asbestos in floor tiles, ceiling tiles, and pipe insulation. Older HVAC systems may not meet current ventilation standards.
• Water damage and mold. Leaks in roofs, walls, or plumbing feed mold growth. Damp classrooms are linked to higher asthma rates.
• Site location. California SB 352 (2003) restricts new schools within 500 feet of a busy roadway. Roadway pollutants can affect health out to about 1,320 feet, and most US schools predate the law. Nearly 1 in 5 schools opened in 2014 to 2015 was built by a busy road.
• Fresh-air intake location. If intakes face a loading dock, bus line, parking lot, or kitchen exhaust, the "fresh" air is anything but.
• Portable classrooms. Often have weaker ventilation, more off-gassing materials, and higher CO2 than main buildings.

Who is most affected

Children with asthma, allergies, or chronic respiratory conditions feel poor classroom air first. Staff and teachers with longer cumulative exposure are at risk too. EPA estimates roughly half of US schools have indoor air quality problems serious enough to affect health and learning.

What to ask your school

If you're a parent, board member, or staffer, push for clear answers:

• What MERV rating is the HVAC filter? Aim for MERV 13 or higher. Many districts upgraded during COVID; some have reverted.
• Where are the fresh-air intakes located relative to traffic and loading docks?
• Is there CO2 monitoring in classrooms? If not, can the district pilot inexpensive sensors?
• What is the protocol for wildfire smoke, ozone alerts, and high-pollen days? Is recess automatically moved indoors?
• When was the building tested for radon, lead in water, lead paint, asbestos, and mold? Are reports public?
• Are there portable HEPA units in classrooms, particularly those nearest traffic or in poorly ventilated areas?

What you can do as a parent

• Ask for the school's most recent indoor air quality and HVAC inspection reports. EPA's IAQ Tools for Schools program offers a framework.
• Donate or fundraise for HEPA units if the district won't pay. A good filter for a classroom runs $200 to $500.
• Manage your child's exposure. If your child has asthma, work with the school nurse on an action plan that accounts for outdoor air quality alerts.
• Vote on school board issues that include HVAC capital projects. Ventilation upgrades are usually the highest health-return-per-dollar item in any school bond.
• For your own home, treat after-school hours as recovery time: low-VOC environment, good filtration, hydration, outdoor time when air is clean.

Sources

• ASHRAE Position Document on Indoor Carbon Dioxide
• Air Quality Monitoring in Schools, Ventilation and Cognitive Performance (PMC)
• California SB 352: Schoolsites Sources of Pollution
• EPA: Best Practices for Reducing Near-Road Pollution Exposure at Schools (PDF)
• EPA: IAQ Tools for Schools
• SCAQMD: Air Quality Guidance for Schools (PDF)
• Center for Public Integrity: The invisible hazard afflicting thousands of schools