Carbon Monoxide | American Lung Association

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Carbon Monoxide

What is carbon monoxide?

Carbon monoxide (CO) is an odorless, colorless, but dangerous gas. Carbon monoxide is produced when fuels are burned, such as gasoline, natural gas, oil, kerosene, wood or charcoal. Breathing CO reduces the blood's ability to carry oxygen. It can reach dangerous levels indoors or outdoors.

Sources include:

  • Gas appliances (furnaces, ranges, ovens, water heaters, clothes dryers, etc.)
  • Fireplaces, wood stoves
  • Coal or oil furnaces
  • Space heaters or oil or kerosene heaters
  • Charcoal grills, camp stoves
  • Gas-powered lawn mowers and power tools
  • Automobile exhaust fumes

What are the health effects of carbon monoxide?

Once inhaled, CO attaches to the hemoglobin in the red blood cells. Hemoglobin normally carries oxygen throughout the body. When CO attaches, it blocks the oxygen the body must have, creating a wide range of health problems.

Breathing low levels of CO can cause:

  • Headache
  • Nausea
  • Dizziness
  • Weakness
  • Confusion
  • Disorientation 1

Many of these symptoms are similar to the flu, food poisoning or other illnesses. So you may not suspect CO poisoning. If symptoms persist, and especially if they get better after you leave the building, CO may be the cause.

Breathing higher levels of CO causes flu-like symptoms such as headaches, dizziness and weakness in healthy people.

Breathing high levels of CO also can cause:

  • Sleepiness
  • Nausea
  • Anxiety or depression
  • Vomiting
  • Confusion
  • Impaired vision
  • Impaired coordination
  • Disorientation 2

Breathing CO at low levels regularly may cause permanent mental or physical problems. At very high levels, it causes loss of consciousness and death. 2

Approximately 430 people die each year from CO exposure related to fuel-burning, residential appliances. Thousands more became ill or sought medical attention. 3 CO poisoning is estimated to cause more than 50,000 emergency room visits in the United States each year. 2

In addition, outdoor air can have too much CO, especially near roads where tailpipe emissions can build up.4 Carbon monoxide can also react with other gases to form ozone pollution.

How can you protect yourself from carbon monoxide?

After an emergency or power outage, be sure to remember these steps so you don't risk your family’s health. Too many people are poisoned by CO after bad weather emergencies, like snowstorms and hurricanes. You may need to seek shelter elsewhere until the electricity is back.

  1. Make sure all appliances work and are fully vented.
    • Make sure appliances are installed and working according to manufacturers' instructions and local building codes.
    • Never use unvented appliances — make sure all appliances are fully vented to the outdoors.
    • Have the heating system, chimney and flue inspected and cleaned by a qualified technician every year.
    • Make sure your furnace has an adequate intake of outside air.
  2. Use appliances and stoves appropriately.
    • Do not use ovens and gas ranges to heat your home.
    • Do not burn charcoal, kerosene lanterns or portable camp stoves inside a home, cabin, recreational vehicle or camper.
  3. Keep carbon monoxide out of your home.
    • Do not operate gasoline-powered engines in confined areas such as garages or basements.
    • Never leave your car or mower running in a closed garage.
    • If you must use a portable generator in an emergency, keep it as far away from your home as possible and away from windows or doors.
    • Never let anyone smoke inside your home. Cigarettes, pipes and cigars also produce carbon monoxide.
  4. Install a CO detector with an audible alarm in your home and garage.
  5. Don't exercise along a busy street or highway.

After an emergency or power outage, be sure to remember these steps so you don't risk your family's health. Too many people are poisoned by CO after bad weather emergencies, like snowstorms and hurricanes. You may need to seek shelter elsewhere until the electricity is back.

Should I buy a carbon monoxide detector?

Yes. Every home should have a working CO detector; it may save your life.
CO detectors should:

  • Meet Underwriters Laboratories, Inc. standards;
  • Have a long-term warranty; and
  • Be easily self-tested and reset to ensure proper functioning.

For maximum effectiveness while you sleep, CO detectors should be placed as close to sleeping areas as possible.

What should I do if the carbon monoxide detector goes off?

  • Make sure it is your CO detector and not your smoke detector.
  • Check to see if any member of the household is experiencing symptoms of CO poisoning.
  • If they are, get them out of the house immediately and seek medical attention. Tell the doctor that you suspect CO poisoning.
  • If no one is feeling symptoms, ventilate the home with fresh air and turn off all potential sources of CO. That includes your oil or gas furnace, gas water heater, gas range and oven, gas dryer, gas or kerosene space heater, and any vehicle or small engine.
  • Have a qualified technician inspect your fuel-burning appliances and chimneys. They can make sure everything is operating correctly and nothing is blocking fumes from being vented outside.
  • Sources
    1. Raub JA, Matheieu-Nolf M, Hampson NB,Thom SR. Carbon Monoxide Poisoning—A Public Health Perspective. 2000. Toxicology 145: 1-14.
    2. Weaver LK. Carbon Monoxide Poisoning. 2009. New England Journal of Medicine 360: 1217-1225.
    3. Centers for Disease Control and Prevention. QuickStats: Average Annual Number of Deaths and Death Rates from Unintentional, Non–Fire-Related Carbon Monoxide Poisoning,*† by Sex and Age Group — United States, 1999–2010. Morbidity and Mortality Weekly Report (January 24, 2014) 63(03):65.
    4. U.S. EPA. 2010 Final Assessment: Integrated Science Assessment for Carbon Monoxide. U.S. Environmental Protection Agency, Washington, DC, EPA/600/R-09/019F, 2010.

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