Indoor Air Quality (IAQ)

EPA 402/F-08/008 | September 2008 | www.epa.gov/iaq

Care for Your Air: 

A Guide to Indoor 

Air Quality
Understand indoor air in 

homes, schools, and offices 

Most of us spend much of our time indoors. The 

air that we breathe in our homes, in schools, and 

in offices can put us at risk for health problems. 

Some pollutants can be chemicals, gases, and 

living organisms like mold and pests.

Several sources of air pollution are in homes, 

schools, and offices. Some pollutants cause health 

problems such as sore eyes, burning in the nose 

and throat, headaches, or fatigue. Other pollutants 

cause or worsen allergies, respiratory illnesses 

(such as asthma), heart disease, cancer, and 

other serious long-term conditions. Sometimes 

individual pollutants at high concentrations, such 

as carbon monoxide, cause death. 

Some pollutants in the air are 

especially harmful for children, 

elderly people, and those with 

health problems.
Learn about pollutants

Understanding and controlling some of the common 

pollutants found in homes, schools, and offices may help 

improve your indoor air and reduce your family’s risk of 

health concerns related to indoor air quality (IAQ).

Radon is a radioactive gas that is formed in the soil. It can 

enter indoors through cracks and openings in floors and 

walls that are in contact with the ground.

 Radon is the leading cause of lung cancer among 

nonsmokers, and the second leading cause of lung cancer 

overall.

Secondhand smoke comes from burning tobacco products. 

It can cause cancer and serious respiratory illnesses. 

 Children are especially vulnerable to secondhand smoke. 

It can cause or worsen asthma symptoms and is linked to 

increased risks of ear infections and Sudden Infant Death 

Syndrome (SIDS).

Combustion Pollutants are gases or particles that come 

from burning materials. In homes, the major source of 

combustion pollutants are improperly vented or unvented 

fuel-burning appliances such as space heaters, woodstoves, 

gas stoves, water heaters, dryers, and fireplaces. The types 

and amounts of pollutants produced depends on the type of 

appliance, how well the appliance is installed, maintained, 

and vented, and the kind of fuel it uses. Common 

combustion pollutants include:

 Carbon monoxide (CO) which is a colorless, odorless 

gas that interferes with the delivery of oxygen 

throughout the body. Carbon monoxide causes 

headaches, dizziness, weakness, nausea, and even death. 

 Nitrogen dioxide (NO2) which is a colorless, odorless 

gas that causes eye, nose and throat irritation, shortness 

of breath, and an increased risk of respiratory infection. 

Volatile organic compounds (VOCs) are chemicals found 

in paints and lacquers, paint strippers, cleaning supplies, 

varnishes and waxes, pesticides, building materials 

and furnishings, office equipment, moth repellents, air 

fresheners, and dry-cleaned 

clothing. VOCs evaporate into 

the air when these products are 

used or sometimes even when 

they are stored. 

 Volatile organic compounds 

irritate the eyes, nose and 

throat, and cause headaches, 

nausea, and damage to the 

liver, kidneys, and central 

nervous system. Some of them can cause cancer.

Asthma triggers are commonly found in homes, schools, 

and offices and include mold, dust mites, secondhand 

smoke, and pet dander. A home may have mold growing on 

a shower curtain, dust mites in pillows, blankets or stuffed 

animals, secondhand smoke in the air, and cat and dog 

hairs on the carpet or floors. Other common asthma triggers 

include some foods and pollutants in the air.

 Asthma triggers cause symptoms including coughing, 

chest tightness, wheezing, and breathing problems. An 

asthma attack occurs when symptoms keep getting worse 

or are suddenly very severe. Asthma attacks can be life 

threatening. However, asthma is controllable with the 

right medicines and by reducing asthma triggers.

Molds are living things that produce spores. Molds produce 

spores that float in the air, land on damp surfaces, and grow. 

 Inhaling or touching molds can cause hay fever-type 

symptoms such as sneezing, runny nose, red eyes, and 

skin rashes. Molds can also trigger asthma attacks.

www.epa.gov/iaq
Improving your air

Take steps to help improve your air quality and reduce your 

IAQ-related health risks at little or no cost by:

Controlling the sources of pollution: Usually the 

most effective way to improve indoor air is to eliminate 

individual sources or reduce their emissions. 

Ventilating: Increasing the amount of fresh air brought 

indoors helps reduce pollutants inside. When weather 

permits, open windows and doors, or run an air conditioner 

with the vent control open. Bathroom and kitchen fans that 

exhaust to the outdoors also increase ventilation and help 

remove pollutants. 

Always ventilate and follow manufacturers’ instructions 

when you use products or appliances that may release 

pollutants into the indoor air. 

Changing filters regularly: Central heaters and air 

conditioners have filters to trap dust and other pollutants in 

the air. Make sure to change or clean the filters regularly, 

following the instructions on the package.

Adjusting humidity: The humidity inside can affect the 

concentrations of some indoor air pollutants. For example, 

high humidity keeps the air moist and increases the 

likelihood of mold.

Keep indoor humidity between 30 and 50 percent. Use a 

moisture or humidity gauge, available at most hardware 

stores, to see if the humidity in your home is at a good 

level. To increase humidity, use a vaporizer or humidifier. 

To decrease humidity, open the windows if it is not humid 

outdoors. If it is warm, turn on the air conditioner or adjust 

the humidity setting on the humidifier.

Important tips that will help control indoor 

pollutants

• Test for radon and fix if there is a problem.

• Reduce asthma triggers such as mold and dust 

mites.

• Do not let people smoke indoors.

• Keep all areas clean and dry. Clean up any mold and 

get rid of excess water or moisture. 

• Always ventilate when using products that can 

release pollutants into the air; if products must be 

stored following use, make sure to close tightly. 

• Inspect fuel-burning appliances regularly for leaks, 

and make repairs when necessary.

• Consider installing a carbon monoxide alarm.
Remodeling old homes and building new homes 

While remodeling or improving the energy efficiency of 

your home, steps should be taken to minimize pollution 

from sources inside the home, either from new materials or 

from disturbing materials already in the home. In addition, 

residents should be alert to signs of inadequate ventilation, 

such as stuffy air, moisture condensation on cold surfaces, 

or mold and mildew growth. 

When building new homes, homebuyers today are 

increasingly concerned about the IAQ of their homes. 

Pollutants like mold, radon, carbon monoxide, and toxic 

chemicals have received greater attention than ever as 

poor IAQ has been linked to a host of health problems. 

To address these concerns, builders can employ a variety 

of construction practices and technologies to decrease the 

risk of poor IAQ in their new homes using the criteria from 

EPA’s Indoor airPLUS as a guide.

To help ensure that you will have good IAQ in your new or 

remodeled home:

 Ask about including radon-reducing features. 

 Provide proper drainage and seal foundations in new 

construction. 

 Consider installing a mechanical ventilation system. 

Mechanical ventilation systems introduce fresh air using 

ducts and fans, instead of relying on holes or cracks in 

the walls and windows. 

 When installing new appliances (like furnaces) make 

sure they are installed properly with a good vent or flue.
With nearly 56 million people, or 20 percent of the U.S. population, spending their days inside elementary and secondary 

schools, IAQ problems can be a significant concern. All types of schools—whether new or old, big or small, elementary 

or high school—can experience IAQ problems. School districts are increasingly 

experiencing budget shortfalls and many are in poor condition, leading to a host of 

IAQ problems. 

 EPA’s voluntary Indoor Air Quality Tools for Schools Program provides districtbased guidance to schools about best practices, industry guidelines, and practical 

management actions to help school personnel identify, solve, and prevent IAQ 

problems. 

 Children may be more sensitive to pollution, and children with asthma are 

especially sensitive. Asthma is responsible for millions of missed school days each 

year. Parents’ and caregivers’ involvement helps daycare facilities become aware 

of asthma triggers and the need to reduce them.

Schools

Office Buildings

Many office buildings have poor IAQ because of pollution sources 

and poorly designed, maintained, or operated ventilation systems. 

 Office workers help to improve the indoor air in their buildings 

by paying attention to environmental conditions including 

ventilation, temperature, and the presence of odors. Report any 

problems to facility managers immediately. 

 To improve IAQ, be careful not to block air vents or grilles, 

keep your space clean and dry, and do not bring in products that 

may pollute the indoor air. 

Unfold this brochure to find a poster that tells you how to improve the air you breathe in your home.

www.epa.gov/iaq
Take Action to Improve Air Quality in Every Room

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VOCs cause eye, nose, and throat irritation, headaches, 

nausea, and can damage the liver, kidney, and central 

nervous system.

Volatile organic compounds (VOCs): are chemicals that evaporate 

at room temperature. VOCs are emitted by a wide array of products 

used in homes including paints and lacquers, paint strippers, 

varnishes, cleaning supplies, air fresheners, pesticides, building 

materials, and furnishings. VOCs are released from products into the 

home both during use and while stored. 

 Read and follow all directions and warnings on common 

household products. 

 Make sure there is plenty of fresh air and ventilation (e.g., opening 

windows and using extra fans) when painting, remodeling, or 

using other products that may release VOCs. 

 Never mix products, such as household cleaners, unless directed to 

do so on the label. 

 Store household products that contain chemicals according to 

manufacturers’ instructions. 

 Keep all products away from children!

Carbon monoxide causes headaches, dizziness, 

disorientation, nausea and fatigue, and high levels can 

be fatal.

Nitrogen dioxide causes eyes, nose, and throat 

irritation, impairs lung function, and increases 

respiratory infections.

Sources include: indoor use of furnaces, gas stoves, unvented 

kerosene and gas space heaters, leaking chimneys, and tobacco 

products.

 Ventilate rooms where fuel-burning appliances are used.

 Use appliances that vent to the outside whenever possible.

 Ensure that all fuel-burning appliances are properly installed, used, 

adjusted, and maintained.

Asthma is a serious, sometimes life-threatening 

respiratory disease that affects the quality of life for 

millions of Americans. 

Environmental asthma triggers: are found around the home and 

can be eliminated with simple steps. 

 Don’t allow smoking in your home or car.

 Dust and clean your home regularly.

 Clean up mold and fix water leaks.

 Wash sheets and blankets weekly in hot water.

 Use allergen-proof mattress and pillow covers.

 Keep pets out of the bedroom and off soft furniture.

 Control pests—close up cracks and crevices and seal leaks; 

don’t leave food out.

Children are especially sensitive to secondhand 

smoke, which can trigger asthma and other 

respiratory illnesses. 

Secondhand smoke: smoke comes from burning tobacco 

products such as cigarettes, pipes, and cigars. 

 To help protect children from secondhand smoke, do not 

smoke or allow others to smoke inside your home or car.

Mold can lead to allergic reactions, asthma, and other 

respiratory ailments.

Mold: can grow anywhere there is moisture in a house. 

 The key to mold control is moisture control.

 If mold is a problem in your home, you should clean up the mold 

promptly and fix the water problem.

 It is important to dry water-damaged areas and items within 24-48 

hours to prevent mold growth.

Radon is the second leading cause of lung cancer.

Radon gas: enters your home through cracks and openings in 

floors and walls in contact with the ground. 

 Test your home with a do-it-yourself radon kit. If the test 

result indicates you should fix, call a qualified radon mitigation 

specialist. 

 Ask your builder about including radon-reducing features in 

your new home at the time of construction.