Carbon monoxide. Sources include unvented fossil-fuel space heaters, unvented gas stoves and ovens, blocked chimneys or flues, idling cars or other engines in garages, and "backdrafting" from furnaces and water heaters.
Check out the Carbon Monoxide or Home IAQ Overview Instructional Modules from our Training Manual for more information, or read some Q&A below.

To protect yourself and your family from carbon monoxide, find out whether you're at risk. Here are some common questions and answers.

Q: How does carbon monoxide get into the home?
A: 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. 

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 by-products 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. 

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

Q: What signs can help me determine if carbon monoxide is affecting my health?
A: Carbon monoxide may be the problem if you feel bad only when you're inside the home and the symptoms gradually disappear after you have left, or if more than one person in the home has similar symptoms. Remember carbon monoxide-related symptoms are similar to those of the flu. 

Q: How can I reduce the risk from carbon monoxide?
A: 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.