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Wisconsin Department of Health Services

Carbon Monoxide

Also known as: Carbonic Oxide, Flue Gas, CO Carbon Oxide
Chemical reference number (CAS): 630-08-0

What is Carbon Monoxide?

Carbon monoxide (CO) is an odorless, colorless gas. Itís formed during incomplete burning of fuels, such as gasoline, kerosene, natural gas, oil, coal, or wood.

Carbon monoxide is also found in cigarette smoke and vehicle exhaust. In homes, carbon monoxide can quickly build up from a poorly vented or malfunctioning heater, furnace, range or any fuel-powered appliance, or even from a car left idling in a garage.

Carbon monoxide is the most common cause of fatal poisonings. Wisconsin State Law (exit DHS; 23 KB) now requires carbon monoxide (CO) detectors in all residences in Wisconsin.

How can I be exposed to Carbon Monoxide?

People can be exposed to dangerous levels of CO when charcoal, gas, oil, or wood are burned in poorly ventilated areas. Breathing automobile exhaust in a closed area can also result in CO poisoning.

Gas-fueled furnaces and water heaters can produce dangerous CO levels if they are malfunctioning. Common situations for CO poisoning include: using gasoline powered generators indoors, idling automobiles in enclosed garages, using propane heaters indoors, and allowing children to ride inside enclosed truck beds. Smoke from tobacco products and wood fires also contains carbon monoxide.

About 50% of all CO poisonings occur in the home. Other common settings include cars, cabins, and tents. About 40% of CO poisonings are automobile-related and 10% occur at worksites. Work exposure is more likely where fuel-powered engines are used in enclosed areas.

What are the effects of Carbon Monoxide exposure?

Exposure to low levels of this odorless gas can produce a throbbing headache, dizziness, fatigue, mental confusion, and shortness of breath. Higher exposures result in severe headache, weakness, dizziness, nausea, irregular heartbeat, and unconsciousness.

Occasionally, these symptoms can be mistaken for symptoms of the flu. Exposure to very high levels of carbon monoxide can cause seizures, coma, respiratory failure, and death. Exposure during pregnancy is associated with birth defects and fetal death.

In addition to the toxic effects of CO, this gas is very flammable and high concentrations may be explosive.

In general, chemicals affect the same organ systems in all people who are exposed. However, the seriousness of the effects may vary from person to person. A person's reaction depends on several things, including individual health, heredity, previous exposure to chemicals including medicines, and personal habits such as smoking or drinking. Itís also important to consider the length of exposure to the chemical.

How can I avoid exposure?

  • Have your furnace, gas stove, and fireplace checked annually by a qualified professional. Have the professional check for proper ventilation and function.
  • All homes must be equipped with carbon monoxide detectors (exit DHS; PDF 23 KB). Carbon monoxide detectors function similarly to smoke detectors and are available at most hardware stores.
  • Make sure the exhaust system on your automobile is in good working condition.
  • Do not ride inside campers or trailers that are being towed by another vehicle.
  • Never run an engine in an enclosed space, such as a garage. This includes cars, snowmobiles, generators, and lawn mowers.
  • Never use a gas oven to heat a home.
  • Never use a charcoal grill indoors.

What do I do if I suspect a problem?

If your CO detector alarms or if you experience any of the above symptoms and suspect carbon monoxide exposure, take immediate action. Get fresh air immediately.  Call your local fire department and move everyone outdoors into fresh air.  Do not re-enter the building until it has been inspected and declared safe.  

Carbon monoxide is eliminated from the body over a period of hours.  Although CO levels can be measured in exhaled breath, urine, blood and other tissues, no reliable method exists to determine the level of your exposure.

For more information:

Environmental Health Home

Air Issues

Toxic Chemical Fact Sheets

Last Revised:  February 24, 2014