Combustion Appliances

Sources of combustion pollutants:

  • furnaces or boilers, water heaters, space heaters, gas ranges and ovens, gas fryers, welding and soldering tools, exhaust from engines operating in attached garages or buildings, or from idling vehicles outside the building.
  • when appliances are not working properly
  • when they are not vented to the outside of the building, or fans are not working
  • when the fumes from outside enter the building through open windows or through the intakes of the HVAC system (for example, when flues or chimneys are not placed well or are too short)
  • when flues or chimneys become blocked
  • when furnaces or boilers have cracks or leaks or when they are not sealed properly from the rest of the building

Health effects:

  • can be mildly irritating to lethal
  • symptoms can include: headaches, dizziness, nausea, sleepiness, irritation to the eyes, difficulty breathing and respiratory problems, coma and death.

Gases released:

Gases released from combustion appliances include (but are not limited to): formaldehyde, nitric oxide, sulfur dioxide, carbon dioxide, carbon monoxide, nitrogen dioxide, and hydrogen cyanide.

  • Carbon monoxide (CO) is produced by any fuel that contains carbon. It is colorless, tasteless and odorless which is why it is such a deadly gas. It can kill before a person realizes what is happening. The symptoms of this gas are: headache, dizziness, weakness, confusion, nausea, vomiting and in extreme cases unconsciousness and even death.
  • Nitrogen dioxide (NO2) can be a respiratory irritant and can cause shortness of breath and increased incidences of respiratory illness. Individuals with asthma and other respiratory illnesses are at greater risk from NO2 exposure.
  • Sulfur dioxide (SO2) can also pose a risk for individuals with asthma. This gas is an eye, nose and respiratory tract irritant. It can also cause chest tightness, wheezing and breathing difficulties.


  • Warde, John. The Healthy Home Handbook: All You Need to Know to Rid Your Home of Health & Safety Hazards. Toronto: Random House Inc., 1997.
  • “What You Should Know About Combustion Appliances and Indoor Air Pollution.” American Lung Association, the US Consumer Product Safety Commission, the US Environmental Protection Agency. 1997.

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