Sources of Indoor Air Pollution - Respirable Particles/Combustion Products

Stoves, Heaters, Fireplaces, and Chimneys

Health Effects of Combustion Products
Sources of Combustion Products
Health Effects
Levels in Homes
Reducing Exposure to Combustion Products in Homes
Steps to Reduce Exposure to Respirable Particles
Subject-Specific Publications

[This information originates from the EPA publication, "The Inside Story - A Guide to Indoor Air Quality."]

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

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 colorless, odorless 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.

Sources of Combustion Products

Fireplaces, wood stoves, and kerosene heaters. Environmental tobacco smoke.

Health Effects

Eye, nose, and throat irritation; respiratory infections and bronchitis; lung cancer.

Levels in Homes

Particle levels in homes without smoking or other strong particle sources are the same as, or lower than, outdoor levels.

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 pilotless 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, 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.  Read the booklet What You Should Know About Combustion Appliances and Indoor Air Pollution to learn more about combustion pollutants.

Steps to Reduce Exposure to Respirable Particles

• Vent all furnaces to outdoors; keep doors to rest of house open when using unvented space heaters.
• Choose properly sized woodstoves, certified to meet EPA emission standards; make certain that doors on all woodstoves fit tightly.
• Have a trained professional inspect, clean, and tune-up central heating system (furnace, flues, and chimneys) annually.  Repair any leaks properly.
• Change filters on central heating and cooling systems and air cleaners according to manufacturer's directions.

Subject-Specific Publications

Should You Have the Air Ducts In Your Home Cleaned? October 1997 (402-K-97-002)

This EPA publication is intended to help consumers answer this often confusing question. The guide explains what air duct cleaning is, provides guidance to help consumers decide whether to have the service performed in their home, and provides helpful information for choosing a duct cleaner, determining if duct cleaning was done properly, and how to prevent contamination of air ducts.

Indoor Air Fact Sheet No. 7 - Residential Air Cleaners, February 1990 (20-A-4001)

Discusses air cleaning as a method of reducing pollutants in indoor air. Lists types of air cleaners for the home, factors to consider in selecting an air cleaner, and sources of additional information. U.S. EPA, Office of Air and Radiation, EPA Document Number 20A-4001, February 1990.

Indoor Air Fact Sheet No. 8 - Use and Care of Home Humidifiers, February 1991 (402-F-91-101)

Explains that some types of home humidifiers can disperse microorganisms from their water tanks into the indoor air. Describes the different types of humidifiers and provides recommendations for their use and maintenance.

Ozone Generators That Are Sold As Air Cleaners, April 1998

The purpose of this document (which is only available via this web site) is to provide accurate information regarding the use of ozone-generating devices in indoor occupied spaces. This information is based on the most credible scientific evidence currently available.

Residential Air-Cleaning Devices: A Summary of Available Information, February 1990 (400/1-90-002)

Describes the general types of residential air cleaners and their effectiveness in reducing pollutants such as particles and gaseous contaminants. This detailed booklet discusses additional factors to consider when deciding whether to use an air cleaner, and provides guidelines to compare them.

What You Should Know About Combustion Appliances and Indoor Air Pollution, 1993 (400-F-91-100)

Answers commonly-asked questions about the effect of combustion appliances (e.g., fuel-burning furnaces, space heaters, kitchen ranges, and fireplaces) on indoor air quality and human health. Describes other sources of combustion pollutants in and around the home. Suggests ways to reduce exposure to such pollutants and encourages proper installation, use, and maintenance of combustion appliances. This brochure was prepared by the U.S. Consumer Product Safety Commission, the American Lung Association, and the EPA.