An Introduction to Indoor Air Quality (IAQ)
Sources of Combustion Products
Basic Information on Pollutants and Sources of Indoor Air Pollution
- Biological Pollutants
- Carbon Monoxide (CO)
- Formaldehyde/Pressed Wood Products
- Lead (Pb)
- Nitrogen Dioxide (NO2)
- Radon (Rn)
- Respirable Particles
- Secondhand Smoke/ Environmental Tobacco Smoke
- Stoves, Heaters, Fireplaces, and Chimneys
- Volatile Organic Compounds (VOCs)
In addition to environmental tobacco smoke, other sources of combustion products are unvented kerosene and gas space heaters, woodstoves, fireplaces, and gas stoves. The major pollutants released are carbon monoxide, nitrogen dioxide, and particles. Unvented kerosene heaters may also generate acid aerosols.
Combustion gases and particles also come from chimneys and flues that are improperly installed or maintained and cracked furnace heat exchangers. Pollutants from fireplaces and woodstoves with no dedicated outdoor air supply can be "back-drafted" from the chimney into the living space, particularly in weatherized homes.
- Health Effects of Combustion Products
- Reducing Exposure to Combustion Products in Homes
- Additional Resources
Health Effects of Combustion Products
Carbon monoxide is a colorless, odorless gas that interferes with the delivery of oxygen throughout the body. At high concentrations can cause a range of symptoms from headaches, dizziness, weakness, nausea, confusion, and disorientation, to fatigue in healthy people and episodes of increased chest pain in people with chronic heart disease. The symptoms of carbon monoxide poisoning are sometimes confused with the flu or food poisoning. Fetuses, infants, elderly people, and people with anemia or with a history of heart or respiratory disease can be especially sensitive to carbon monoxide exposures.
Nitrogen dioxide is a reddish brown, irritating odor gas that irritates the mucous membranes in the eye, nose, and throat and causes shortness of breath after exposure to high concentrations. There is evidence that high concentrations or continued exposure to low levels of nitrogen dioxide increases the risk of respiratory infection; there is also evidence from animals studies that repeated exposures to elevated nitrogen dioxide levels may lead, or contribute, to the development of lung disease such as emphysema. People at particular risk from exposure to nitrogen dioxide include children and individuals with asthma and other respiratory diseases.
Particles, released when fuels are incompletely burned, can lodge in the lungs and irritate or damage lung tissue. A number of pollutants, including radon and benzo(a)pyrene, both of which can cause cancer, attach to small particles that are inhaled and then carried deep into the lung.
Reducing Exposure to Combustion Products in Homes
- Take special precautions when operating fuel-burning unvented space heaters.
Consider potential effects of indoor air pollution if you use an unvented kerosene or gas space heater. Follow the manufacturer's directions, especially instructions on the proper fuel and keeping the heater properly adjusted. A persistent yellow-tipped flame is generally an indication of maladjustment and increased pollutant emissions. While a space heater is in use, open a door from the room where the heater is located to the rest of the house and open a window slightly.
- Install and use exhaust fans over gas cooking stoves and ranges and keep the burners properly adjusted.
Using a stove hood with a fan vented to the outdoors greatly reduces exposure to pollutants during cooking. Improper adjustment, often indicated by a persistent yellow-tipped flame, causes increased pollutant emissions. Ask your gas company to adjust the burner so that the flame tip is blue. If you purchase a new gas stove or range, consider buying one with pilot less ignition because it does not have a pilot light that burns continuously. Never use a gas stove to heat your home. Always make certain the flue in your gas fireplace is open when the fireplace is in use.
- Keep woodstove emissions to a minimum. Choose properly sized new stoves that are certified as meeting EPA emission standards.
Make certain that doors in old woodstoves are tight-fitting. Use aged or cured (dried) wood only and follow the manufacturer's directions for starting, stoking, and putting out the fire in woodstoves. Chemicals are used to pressure-treat wood; such wood should never be burned indoors. (Because some old gaskets in woodstove doors contain asbestos, when replacing gaskets refer to the instructions in the CPSC, ALA and EPA booklet, Asbestos in Your Home - www.epa.gov/asbestos/pubs/ashome.html, to avoid creating an Asbestos problem. New gaskets are made of fiberglass.)
- Have central air handling systems, including furnaces, flues, and chimneys, inspected annually and properly repair cracks or damaged parts.
Blocked, leaking, or damaged chimneys or flues release harmful combustion gases and particles and even fatal concentrations of carbon monoxide.
Strictly follow all service and maintenance procedures recommended by the manufacturer, including those that tell you how frequently to change the filter. If manufacturer's instructions are not readily available. change filters once every month or two during periods of use. Proper maintenance is important even for new furnaces because they can also corrode and leak combustion gases, including carbon monoxide.
EPA's Cookstoves Program
The World Summit on Sustainable Development in Johannesburg addressed the increased environmental health risk faced by more than 2 billion people in the developing world who burn traditional biomass fuels indoors for cooking and heating. According to the World Health Organization, their increased exposure results in an estimated 1.6 million premature deaths each year, largely among women and children. The mission of the Partnership is to improve health, livelihood, and quality of life by reducing exposure to air pollution, primarily among women and children, from household energy use. Read more about EPA's Cookstove Program.
EPA Fact Sheet Protect Your Family and Yourself from Carbon Monoxide Poisoning (PDF) (2 pp., 65 K, About PDF)
Proteja su vida y la de su familia: Evite el envenenamiento con monóxido de carbono (PDF) (3 pp., 63 K) The Carbon Monoxide fact sheet has also been translated into Vietnamese, Chinese and Korean languages.
National Fire Protection Association - www.nfpa.org
(Offers information on codes and standards, safety information, training and research.) Quincy, Massachusetts, Tel: (617) 770-3000 / Fax: (617) 770-0700