The Medical Minute: Carbon monoxide is a silent killer

December 22, 2004

By John Messmer
Department of Family and Community Medicine
Penn State Milton S. Hershey Medical Center
Penn State College of Medicine

Carbon monoxide is a gas produced when something is burned. In the home, fuel-burning appliances, whether gas, oil or wood, are sources of carbon monoxide as are charcoal and propane grills. Electric appliances do not produce carbon monoxide.

As long as the burning substance has enough air to provide oxygen and the combustion vents properly, the gas need not be a worry. So why is it the No. 1 cause of unintentional poisoning death in the world? Carbon monoxide kills about 500 people in the United States annually, while another 4,000 are treated for carbon monoxide poisoning, according to the Centers for Disease Control. Many times people are harmed or killed by carbon monoxide because of something they overlooked or because of a simple error in judgment.

Carbon monoxide has no odor or color, making it difficult for people to notice. Do not be misled by associating carbon monoxide with the smell of auto exhaust. The odor is caused by residual gasoline byproducts, not carbon monoxide.

The gas can cause headache, fatigue, dizziness, nausea, vomiting and confusion. In people with respiratory or cardiac illness, it can cause chest pain and shortness of breath. Carbon monoxide poisoning is not always immediate. Often the symptoms come and go, making it difficult to determine the cause. However, if levels get high enough, the gas can cause loss of consciousness and death, sometimes without warning during sleep. If several members of the household are experiencing symptoms, suggest carbon monoxide poisoning to a doctor as a possible cause.

To avoid carbon monoxide poisoning, have heaters, chimneys and flues inspected and serviced according to the manufacturer's recommendations. Be sure there is adequate interior ventilation for any inside burning particularly the newer unvented pellet stoves and kerosene space heaters. Never heat a room or house with a gas stove or oven. Do not let a car idle in an attached garage even if the garage door is open as fumes can move into living spaces quickly. In winter, check that the tailpipe is cleared of snow or carbon monoxide in exhaust can back up into the car. Charcoal is a source of carbon monoxide, so never use a charcoal grill indoors and do not use charcoal in a fireplace.

An additional precaution is the use of a carbon monoxide detector for appliances, tools or heaters that burn any type of fuel. A detector is not a substitute for adequate maintenance of the appliance, and it is not the same as a smoke detector. The technology for carbon monoxide detectors is still developing and some are more reliable than others. Check for Underwriters Laboratories (UL) approval and consult an independent review such as Consumers Union for information on brands.

Be sure to position and maintain a carbon monoxide detector according to instructions and change the battery annually at least. Test carbon monoxide and smoke detectors regularly, and if an alarm is heard, be sure it is not the smoke alarm. The smoke alarm should prompt individuals to leave immediately. When the carbon monoxide alarm sounds, check everyone in the house. If anyone is unconscious or confused, get them out of the house and call 911. Otherwise get fresh air and contact a doctor or go to an emergency room for evaluation.

Carbon monoxide can be deadly. But by following a few basic precautions, carbon monoxide deaths and related injuries are generally avoidable.

For more information on carbon monoxide, go to or

The Consumer Products Safety Council ( has information on recalled carbon monoxide monitors, by searching "carbon monoxide."

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Last Updated March 19, 2009