Indoor Air Quality at School

When children with asthma and allergies go to school each day, they carry more than just a backpack and lunch. They also tote a load of worries. Will they cough during the math test? Will they need their inhaler walking the halls between classes? Will they feel chest tightness riding the school bus?

It’s vital that schools identify and reduce or remove allergens and irritants in school buildings. The U.S. Environmental Protection Agency (EPA) says indoor levels of air pollutants may be 2-5 times higher than outdoor air quality. Research has shown that poor indoor air quality can be harmful to student performance in both academics and attendance.

Working together, parents, school nurses, teachers and other school staff can maintain clean indoor air and create a healthy learning environment.

Tween children in a classroom at their desks. Some of them are raising their hands.

School Conditions Affecting Indoor Air Quality

As of 2016, the average age of school buildings in the United States was 44 years old. Nearly a quarter of schools are in fair to poor condition. The age and condition of many school buildings is a problem that can affect schools’ indoor air quality. Other problems include:

  • Poor ventilation systems and filtration (31% of schools)

  • Heating (26%)

  • Air conditioning (28%)

  • Plumbing (26%)

In some cases, the design of the school building, the maintenance, and the materials used can cause poor air flow. Problems with poorly designed heating, ventilation and air conditioning (HVAC) systems and plumbing in schools can increase exposure to indoor pollutants.

The number of students and staff in each classroom or school building and the types of activities performed could also impact indoor air quality.

Maintained properly, the school’s air handling system should trap and filter many particles. It does not purify dirty, polluted air. If school buses or cars pick up and drop off students in the back of the school near air handling equipment, exhaust fume particles will travel throughout the school’s supply lines. And that’s not healthy for anyone.

HVAC professional cleaning and replacing air ducts.

Common allergens and irritants found in classrooms

Even perfectly maintained school buildings cannot protect students and staff from all allergens, irritants and other indoor air pollutants in the classroom.

  • mold (especially if there’s a sink in the classroom)
  • dust (including chalk dust)
  • dry erase markers (they may contain harmful chemicals)
  • paints and glues
  • animal dander, urine or saliva from classroom pets or visiting furry animals
  • animal dander brought in on clothing from pets at home
  • dust mites found in carpeting, mats, pillows or upholstered furniture
  • cockroaches, mice and rats
  • strong odors, such as perfumes or air fresheners
  • cleaning products used by janitorial staff
  • chemicals from science or art projects

If airborne pollutants get into the school’s air handling systems, they can move from one part of the school to another.

Allergens and irritants can also come inside from outdoor air. Open doors and windows may invite pollen to enter during the spring. Exhaust fumes from idling school buses outside the building may also seep into the school building.

Schools do not allow smoking on campus. But thirdhand smoke lingering on clothes can still be a problem and impact student health.

Clues that allergens and irritants are present in school buildings

Many factors affect indoor air quality in schools. It could be the size, type or age of the HVAC system. It could be the presence of mold. It could even be the number of students in each classroom. Sometimes it can be hard to tell if a school has poor indoor air quality. This is particularly the case if HVAC systems are poor or if there’s hidden mold or pests.

HVAC or air handling systems

Clues include:

  • Black or gray powdery dust on ceiling tiles or walls
  • Standing water underneath or near air conditioning
  • Dead animals or insects underneath or near HVAC systems
  • Bird nests near outdoor units


Clues include:

  • Black or brown spots in dark, warm humid areas: bathrooms, locker or shower rooms, basement, under sinks or utility areas and mechanical areas
  • Black or brown spots in closed-in areas: underneath and behind furniture, behind cabinets or in coat closets
  • Discolored or damp carpeting, especially near windows or under water fountains
  • Musty smell among stored papers or books


Clues include:

  • Black or brown pellets (mouse droppings)
  • Dead cockroaches or decaying insect parts
  • Nests
  • Urine stains or smell from pests
  • Dust clumps that have insect droppings and decaying insect parts in them
  • Greasy smears on walls (which could indicate possible rat runs)


A line of children with backpacks excitedly running towards their school

How to Improve Indoor Air Quality at School

Clean air is essential to living and learning. The first step to healthy indoor air quality in schools is to identify what is causing the indoor air pollution. Then take action to protect students and school staff.

Schools should assess indoor air quality regularly. Regular inspection, testing and maintenance are essential. Air quality monitoring devices are available to measure temperature, relative humidity, air flow, and carbon dioxide levels throughout the school. These measurements can set a baseline for where improvements are needed.

Many of our nation’s schools need to better maintain or upgrade inadequate ventilation systems. This will help improve circulation and filtration of fresh air. Some other HVAC recommendations include:

  • Keep ventilation units in classrooms free of clutter.

  • Install high efficiency particulate air (HEPA) filters or MERV-13 (or higher) filters for your HVAC system and air conditioning units.

  • Use a portable HEPA air cleaner to remove larger particles of allergens in classroom air.

  • Open windows on weekends and when pollen counts are low to bring in fresh air. This is natural ventilation.

  • Report any indoor air quality issues and maintenance problems occurring in classrooms and hallways.

In some cases, school buildings may need to replace HVAC systems.

If the school building was built before 1990, it is possible the building materials that were used contain and lead, formaldehyde, and asbestos. These chemicals are often difficult to detect. They can be absorbed into the body and cause a host of symptoms and diseases, including lung disease.

Clues that your school’s air handling system may need servicing:

  • Black or gray powdery dust on ceiling tiles, walls and vent covers 

  • Standing water underneath or near the air handling unit 

  • Dead animals, insects, bird or rodent nests in or near outdoor units


Photo of woman looking at mold on a wall

Repair or remove allergens or irritants at school

Schools should assess for potential allergens and irritants, including those that can trigger asthma and allergies. Parents of children with asthma should talk to the school nurse about removing or avoiding the trigger, if possible. They can also speak with the child’s teacher(s).

EPA developed a guide to address improving indoor air quality in schools – the Indoor Air Quality Tools for Schools Action Kit. The kit includes checklists for school staff, including teachers, school nurses or health officers, school administrators, and others in the school community. The checklists provide practical tools to improve indoor air quality.

Here are some recommendations to improve air quality in schools:


Schools should immediately fix the water or moisture problem, especially plumbing leaks. (The mold will return if you don’t.) Sometimes it’s just a matter of wiping the area around a sink. Other times it may require a plumber to fix a leaky faucet or pipe.

When cleaning, school janitorial staff should avoid using bleach as it can irritate breathing passages. They should use nontoxic, fragrance-free cleaning products. The janitor should wear a mask and goggles to shield nose, mouth and eyes from airborne mold.

Larger areas of indoor mold (greater than 10 square feet) should be cleaned by a professional.

Mold prevention is equally as important. If there’s water-damaged areas on school property, dry them out within 48 hours to prevent mold growth.


If there is an infestation of cockroaches, mice or rats, the school should call a professional exterminator. Chances are if there’s one cockroach, mouse or rat, there are others.

The school should also take steps to prevent these critters from entering the building. These steps may include:

  • Make sure to store food, water and other beverages in tightly closed containers in the classroom overnight. This includes items for class or science projects.

  • Fix plumbing leaks.

  • Seal cracks in walls or under sink areas where cockroaches, mice and rats can enter.

  • Remove unnecessary clutter where pests can hide.

  • Store dumpsters away from the school building.

  • Use poison baits, boric acid or traps before using pesticide sprays.

  • Prevent dust mites by allowing only washable stuffed animals in the classroom. Use a dust-mite proof nap pad or pillow for young students. If possible, replace upholstered furniture and remove carpeting in favor of hardwood floors or solid surface flooring.

Considering pesticides to remove an infestation? Here are some tips for schools to ensure it’s an efficient process:

  • Notify parents and school staff before applying pesticides. 

  • Schedule pesticide applications when areas will be unoccupied and can be well ventilated before occupants return.

  • Use pest control chemicals in strict accordance with regulations and follow instructions on the container.

Animal dander

Whether they live in the classroom or visit for show-and-tell, warm-blooded animals such as hamsters, birds, rabbits, cats and dogs can release dander. It’s best for schools to not allow furry animals in the classroom. Consider a classroom pet fish instead.

Secondhand smoke

Smoking is harmful to everyone’s health, but for people with asthma it can trigger symptoms. Schools should prohibit smoking on school grounds. This includes inside, outdoors, on school buses and at school events.


Additional recommendations for schools and parents

  • Transition away from chalkboards to dry-erase boards. Use no-scent or low-scent dry-erase markers.

  • Establish a “no perfume” classroom rule for students and school employees. This should include cosmetics with a strong scent.

  • Do not use scented air fresheners in the classroom as these can cause asthma flares.

  • Avoid using scented products – art markers, paints, crayons, and disposable wipes. However, even the unscented products may have masking fragrances that cover unpleasant odors. Masking scents added at low concentrations are not always listed on the label.

  • Establish a “no idling” policy for school buses. Exhaust fumes are not only dangerous in parking areas – they can enter school classrooms through ventilation systems.

  • Purchase portable air cleaners and install them in problem areas as needed.

  • Meet with the art and science teachers to ask about alternatives to class projects involving harsh chemicals. Formaldehyde, for example, can causing breathing problems in people with asthma and a burning sensation in the eyes and throat.

  • Keep indoor work or hobby spaces well ventilated and wear dust or vapor masks to protect the airways. Woodworking, sanding, using spray paints, sculpting and other creative hobbies can send tiny pieces of dust into the air. The ones that fall to the ground quickly are less of a problem than those that stay in air for longer periods.

Children in a single file line at the curb as the yellow schoolbus pulls up to pick them up.

Advocate for Healthy Indoor Air Quality at School

Get involved! Parents can partner with teachers and school staff to advocate for good indoor air quality. Attend school board meetings to discuss indoor air problems. Many school districts have an indoor air quality committee that you can join or attend meetings.

Remember to vote in local elections. Elected officials are often those making decisions affecting schools and school administration. There may be initiatives on your ballot to fund school improvements and address poor air quality in schools.

Reviewed by:
William E. Berger, MD, FACAAI, is a board-certified allergist and immunologist who serves as a media spokesperson and Chair of the Medical Advisory Council for Allergy & Asthma Network. He is a Distinguished Fellow and Past President (2002-03) of the American College of Allergy, Asthma & Immunology (ACAAI).