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Carbon Monoxide

What is it?

Carbon monoxide is a colorless, highly poisonous gas. Under pressure, it becomes a liquid. It is produced by burning gasoline, natural gas, charcoal, wood, and other fuels.

Appliances, tools, space heaters, and generators that use these fuels can produce carbon monoxide through incomplete combustion. Vehicle exhaust and tobacco smoke contain carbon monoxide. It can be released from wildfires.

Carbon monoxide is most dangerous in enclosed spaces such as garages or indoor rooms.

See also: Homes Vehicles and Engines Cardiovascular (Heart) Disease

Where is Carbon Monoxide found?

  • Consumer products -  vehicles, appliances, some space heaters, generators, gas-powered tools, and cigarettes
  • Air - vehicle exhaust, cigarette smoke, secondhand smoke, smoke from burning charcoal or wood, and fumes from leaking appliances or space heaters

How can I be exposed to Carbon Monoxide?

Carbon Monoxide commonly enter(s) the body through:

Inhalation (breathing)
  • Breathing vehicle exhaust and fumes from leaking appliances, space heaters, and other fuel-burning products
  • Smoking cigarettes or breathing secondhand smoke

What happens when I am exposed to Carbon Monoxide?

Exposure from breathing carbon monoxide can cause:

  • Headache
  • Nausea and vomiting
  • Blurred vision
  • Confusion
  • Dizziness
  • Chest pain
  • Weakness
  • Difficulty breathing
  • Damage to the heart and brain
  • Unconsciousness

Breathing in high amounts of carbon monoxide is life-threatening.

Exposure from breathing high carbon monoxide levels can cause:

  • Miscarriage
  • Damage to a developing fetus
  • Seizures
  • Coma
  • Heart failure

Who is at risk for exposure to Carbon Monoxide?

  • Consumers
    • Vehicles, some consumer products, and fuels emit carbon monoxide.
  • Cigarette smokers
    • Tobacco products and secondhand smoke contain carbon monoxide.
  • Pregnant women
    • Carbon monoxide can cause miscarriage or damage a developing fetus.

Reduce your risk

If you think your health has been affected by exposure to carbon monoxide, contact your health care professional. 

Always wash your hands thoroughly after handling chemicals. For poisoning emergencies or questions about possible poisons, please contact your local poison control center at 1-800-222-1222.

  • Do you have carbon monoxide and smoke detectors in your home? Do you change the batteries routinely?
  • Do you have furnaces, space heaters, fireplaces, wood stoves, or fuel-burning appliances in your home?
  • Do you have a poorly vented home generator?
  • Do you ever leave the car running in your garage?
  • Do you, or does anyone in your household, smoke tobacco products?
  • How frequently are you exposed to vehicle exhaust or gas stations?
  • Do you own a boat with an engine?
  • Do you live near a busy highway?
  • Have fireplaces and wood stoves professionally checked once a year or as recommended by the manufacturer.  Make sure the flue is open when fireplaces are in use.
  • Make sure space heaters are properly vented during use.
  • Have all fuel-burning appliances and forced-air furnaces checked professionally once a year.
  • Never use gas stoves for supplemental heat.
  • Never use barbecue grills, hibachis, or gas-powered tools indoors or in poorly ventilated spaces such as garages, campers, or tents.
  • Regularly inspect and maintain vehicle exhaust systems.
  • Never leave a vehicle running in a garage or other enclosed space.
  • Limit your time near idling cars, trucks, or buses.
  • When the power goes out, keep your generator outside.
  • Don’t run or exercise near busy highways.
  • If you smoke, quit. Avoid secondhand smoke.
  • Schedule regular boat engine and exhaust system maintenance. Consider installing a carbon monoxide detector in the boat.
  • Never swim under the back deck or swim platform of a boat.
  • Don’t let children play near gas stations, idling cars, or busy highways.
  • Keep children away from fuel-burning appliances and tools.
National Library of Medicine Resources and Databases
Additional Resources
  • Carbon Monoxide (CO) Pollution in Outdoor Air (Environmental Protection Agency)

    Information about carbon monoxide pollution, including outdoor air standards and their implementation.

  • Carbon Monoxide Poisoning and Boating (Centers for Disease Control and Prevention)

    Information about carbon monoxide poisoning due to boating, disasters, and portable generators, as well as clinical education resources, frequently asked questions, podcasts, and prevention guidance.

  • Carbon Monoxide. ToxFAQs (Agency for Toxic Substances and Disease Registry)

    Factsheet with answers to most frequently asked questions about carbon monoxide exposure and its effects on human health, developed by a federal public health agency that protects communities from harmful health effects related to exposure to natural and man-made hazardous substances.

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