Mold in schools is surprisingly common. The EPA estimates that up to half of all schools have problems linked to indoor air quality, and mold is one of the most frequent culprits. Because school buildings are often older, large, and difficult to maintain, they create ideal conditions for mold growth, particularly in hidden spaces behind walls, above ceiling tiles, and inside ventilation systems.
How Common the Problem Really Is
Schools face a unique set of challenges when it comes to mold. Many buildings are decades old with aging roofs, outdated plumbing, and HVAC systems that struggle to keep up. Budget constraints often mean repairs get delayed, and a small leak can quietly feed mold growth for months before anyone notices. About 1 in 13 school-age children have asthma, making them especially vulnerable to the effects of mold exposure. Asthma is already one of the leading causes of school absences for children ages 5 to 17, accounting for an estimated 13.8 million lost school days each year. Mold is one of several indoor triggers that can make that worse.
Health Effects for Students and Staff
Mold triggers allergic reactions in many people. The most common symptoms include sneezing, a runny or stuffy nose, coughing, postnasal drip, itchy or watery eyes, and dry, itchy skin. These symptoms vary widely from person to person. Some people barely notice them, while others are miserable throughout the school day and feel better once they leave the building, a pattern that can be an important clue.
For students and staff with asthma, the stakes are higher. Mold spores can trigger asthma episodes that cause wheezing, shortness of breath, and coughing. In some people, exposure to certain types of mold can set off severe asthma attacks. Children are particularly vulnerable because they breathe faster relative to their body size, taking in more airborne spores per pound of body weight than adults.
Mold can also cause skin or mucous membrane infections in susceptible people, though this is less common. People with weakened immune systems or chronic lung conditions face the greatest risk of serious complications, including a lung reaction called allergic bronchopulmonary aspergillosis. For the average healthy person, mold exposure is unlikely to cause a systemic infection, but the allergic and respiratory symptoms alone are enough to disrupt learning and work performance.
Where Mold Grows in School Buildings
Mold needs only two things: moisture and an organic surface to feed on. It can begin growing on damp materials in just 48 hours. In schools, the most common moisture sources are roof leaks, pipe leaks, and condensation from HVAC systems.
Roof leaks are a leading cause of water intrusion. Even a tiny puncture from a fallen branch or a corroded fastener can let water slowly seep into ceiling materials for weeks before it becomes visible. Pipe leaks behind walls are similarly insidious because they stay hidden, feeding mold colonies that spread inside wall cavities where no one can see them.
HVAC systems deserve special attention. Condensation from cooling coils can drip into ceiling and wall materials or travel along ventilation ducts. When cooling coils become clogged with dirt, air speeds up through the remaining clean sections, carrying more moisture downstream into the ductwork instead of letting it drain properly. Worse, a dirty cooling coil stays continuously wet, creating a perfect surface for mold to colonize. Since cooling coils sit downstream of filters, any mold that grows there gets distributed directly through the duct system and into classrooms.
Other common problem spots include bathrooms, kitchens, locker rooms, basements, and any area where water pools or humidity builds up. Carpeted classrooms that experience even minor flooding are especially risky because porous materials trap moisture deep inside where it’s difficult to dry completely.
Signs That a School Has a Mold Problem
Visible mold is the most obvious sign, but it often hides behind walls, above drop ceilings, or inside ductwork. Musty or earthy odors in certain rooms are a strong indicator, even when nothing is visible. Water stains on ceiling tiles, bubbling or peeling paint, and warped or discolored walls all suggest ongoing moisture problems that likely support mold growth.
A pattern of health complaints can also point to a building issue. If multiple students or staff members in the same area of the school report allergy-like symptoms, headaches, or worsening asthma that improves on weekends and breaks, the indoor environment is a likely factor.
What Cleanup Looks Like
The EPA outlines several cleanup approaches for mold in schools, scaled to the size of the problem. Small areas can often be handled with damp wiping using water and detergent, followed by thorough drying. For larger contamination, the process becomes more involved. HEPA vacuuming is used after affected areas are completely dried, and the vacuum contents are sealed in plastic bags for disposal. Materials that can’t be fully cleaned, like waterlogged ceiling tiles, drywall, or carpeting, need to be removed, bagged while still in the work area, and discarded.
For significant mold contamination, containment is critical. This means sealing off the affected area with plastic sheeting from ceiling to floor, maintaining negative air pressure so spores don’t escape into the rest of the building, and blocking supply and return air vents within the work zone. Full-scale remediation requires two layers of sheeting, an airlock chamber, and filtered air exhausted directly outside the building. Workers wear protective equipment ranging from basic respirators and gloves for small jobs to full-body suits with face respirators for large-scale removal.
The most important part of any cleanup is fixing the moisture source. Removing visible mold without stopping the water intrusion guarantees the problem will return.
Preventing Mold in Schools
The EPA recommends keeping indoor relative humidity below 60%, with an ideal range of 30% to 50%. Staying within this range makes it very difficult for mold to establish itself, even on surfaces that would otherwise be hospitable.
Roof maintenance is a first line of defense. Pitched roofs should have overhangs with gutters and downspouts to direct water away from the building rather than letting it cascade down exterior walls. Flat roofs need clean, free-flowing drains that empty somewhere outside the building, not into interior spaces. Regular inspections catch small problems before they become large ones.
HVAC systems need consistent maintenance. Cooling coils should be kept clean to prevent the moisture bypass and mold growth described above. Filters need regular replacement, and condensate drain lines should be checked for clogs. Ventilation systems that bring in fresh outdoor air help dilute indoor pollutants, but during warm, humid weather, that incoming air may need to be dehumidified before distribution.
Building inspections ideally happen twice a year, typically at the beginning and end of the school year. Schools with ongoing moisture issues should assess more frequently. These inspections should include visual checks of known problem areas: rooflines, pipe chases, bathroom ceilings, HVAC closets, and any space where water damage has occurred before.
What Parents and Staff Can Do
If you suspect mold in your child’s school or your workplace, start by documenting what you see and smell, along with any health symptoms that follow a pattern tied to the building. Report your concerns in writing to school administration. Putting it in writing creates a record and typically prompts a faster response than a verbal complaint.
For school employees, OSHA sets expectations for employers to address mold-related hazards in the workplace. Employers have responsibilities under OSHA’s general industry standards to maintain safe working conditions, which includes addressing known mold contamination. If a school district is unresponsive, staff can file a complaint with OSHA, and parents can escalate concerns to the school board or local health department.
Many states and districts also have their own policies governing indoor air quality in schools. Requesting an indoor air quality assessment through formal channels often moves the process forward, particularly when multiple people report similar symptoms in the same part of a building.