What Is Carbon Monoxide?

CARBON MONOXIDE (CO). CO is produced by unvented kerosene and gas space heaters; leaking chimneys and furnaces; back-drafting from furnaces, gas…

What Is Carbon Monoxide?

Carbon Monoxide, or CO, is produced by:

  • Unvented kerosene and gas space heaters
  • Leaking chimneys and furnaces
  • Backdrafting from furnaces, gas water heaters, woodstoves, fireplaces, gas stoves
  • Automobile exhaust from attached garages can also enter the home
  • Environmental tobacco smoke also produces CO


What is the effect of CO on your health?

At low concentrations, some of the effects of CO exposure are fatigue in healthy people and chest pain in people with heart disease. At higher concentrations, impaired vision and coordination; headaches; dizziness; confusion; nausea.
CO exposure can cause flu-like symptoms that clear up after leaving home.
CO is fatal at very high concentrations.

How does carbon monoxide get into the home?

Carbon monoxide buildup can occur several ways:

    • When flues or chimneys become blocked so exhaust cannot be vented to the outside


    • When a fuel burning furnace has a cracked or rusted heat exchanger, allowing combustion gases into the living spaces


    • When fuel-burning space heaters, ovens, ranges or grills are operated in the home without adequate ventilation


    • When car exhaust from an attached garage enters the home


    • When combustion equipment is not working properly and causes incomplete combustion


  • When there’s a negative pressure balance between the inside and outside of the home, preventing adequate venting of combustion gases.

What causes carbon monoxide to build to dangerous levels?

Harmful build-ups of these gases can occur when: exhaust from combustion equipment is not vented to the outside of the home, and when combustion equipment is not in good working order and is not regularly inspected for safe operation.

Some homes may have a problem with “backdrafting.” That’s when the air pressure inside the home is less than the air pressure outside, causing combustion biproducts from furnaces, water heaters, fireplaces and similar equipment to spill back into the room rather than being vented outside. Backdrafting can also occur when natural draft appliance exhaust is pulled back into the house by mechanical ventilation — like a down-draft kitchen power vent.

Is there a way to detect if my home has carbon monoxide build-up?

There are carbon monoxide alarms you can install, which will alert you to dangerous levels of carbon monoxide. It is important to choose and place an alarm wisely and maintain it to assure accurate sensing of carbon monoxide.

How can I reduce the risk from carbon monoxide?

  • The most important practice is to keep all combustion equipment well-maintained and inspected for safety.


  • Experts recommend having your combustion heating systems inspected by a trained professional every year. Such inspections should look for blocked openings to flues and chimneys; cracked or disconnected flue pipe; signs of soot around openings in your furnace or boiler; rust or cracks in the heat exchanger; soot or creosote build-up; and exhaust or gas odors.


  • Always operate combustion equipment for its intended purpose and make sure it has been installed correctly.


  • Never use unvented combustion appliances indoors.

What is NO2?

Nitrogen Dioxide, or NO2, is produced by kerosene heaters, unvented gas stoves and heaters. NO2 is also produced by smoking cigarettes, pipes and cigars (Environmental tobacco smoke).

What is the effect of NO2 on your health?

Exposure to NO2 may cause eye, nose, and throat irritation. It may also cause impaired lung function and increased respiratory infections in young children.


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