Carbon Monoxide

Why am I being warned about potential exposure to carbon monoxide?

  • Carbon monoxide (CO) is on the Proposition 65 list because it can cause birth defects or other reproductive harm.
  • Exposure to carbon monoxide during pregnancy can affect the baby’s brain development and cause loss of pregnancy.
  • Proposition 65 requires businesses to determine if they must provide a warning about exposures to listed chemicals.

What is carbon monoxide?

  • Carbon monoxide is a colorless, odorless, and  poisonous gas. It is formed during the combustion of various fuels, including gasoline, diesel, natural gas, wood, coal, kerosene, propane, and plant-derived materials, such as tobacco.
  • Carbon monoxide can replace oxygen in the bloodstream. Reduced levels of oxygen in the bloodstream during pregnancy can affect development of the baby’s brain. 

How does exposure to carbon monoxide occur?

Carbon monoxide is produced during combustion
People breathe contaminated air
  • Exposure occurs by breathing air that contains carbon monoxide. Sources include:
    • Incorrectly installed, maintained, and inadequately ventilated cooking and heating appliances such as:
      • Unvented kerosene, gas and water heaters
      • Wood stoves
      • Leaking fireplaces, chimneys and furnaces
      • Charcoal and propane grills that are used inside or in garages or unventilated areas
      • Gas stoves, generators, and other gasoline-powered equipment
    • Motor-vehicle exhaust, which can accumulate in garages, enclosed parking facilities, service stations, and vehicle-repair facilities
    • Other gasoline- and diesel-powered engines such as those used in leaf blowers, lawn mowers, weed trimmers, snow blowers, chain saws, or other small engines
    • Tobacco smoke
  • During pregnancy carbon monoxide can pass from the mother to the baby.

How can I reduce my exposure to carbon monoxide?

  • Ensure that equipment and appliances that produce carbon monoxide are installed correctly, maintained in good condition, and vented to the outside whenever possible.
  • Install a carbon monoxide alarm, test it frequently, and replace its batteries as recommended.
  • Obtain annual inspections for heating systems and chimneys by a trained professional. Make certain that vent pipes, flues and chimneys are properly connected, cleared of any blockages, properly vented to the outside, and otherwise in good condition.
  • Limit time spent in enclosed parking facilities, service stations, and vehicle-repair facilities.
  • Never use kerosene heaters, charcoal grills or barbecues indoors.
  • Do not idle a car in an enclosed garage or shed even if the door is open to the outside. Carbon monoxide present in motor-vehicle exhaust can build up very quickly in garages, sheds and living areas of homes.
  • Never leave any gasoline-powered engines (lawn mowers, weed trimmers, snow blowers, chain saws, or other small engines) running in enclosed spaces.
  • Never use your gas stove or oven to heat the home.
  • Do not use unvented gas fireplaces.
  • Do not use gasoline-burning appliances such as cooking stoves and ranges, generators, or camp stoves in enclosed spaces, including homes, basements, campers, tents, vans, trucks, garages, or mobile homes.
  • Do not smoke. Do not allow children to breathe tobacco smoke.

For more information:

Carbon Monoxide Fact Sheets and Resources:

Proposition 65:

  • California Environmental Protection Agency (CalEPA)
    Office of Environmental Health Hazard Assessment (OEHHA)

Scientific Information on Carbon Monoxide:

Posted May 2016

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