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carbon monoxide detector

Carbon Monoxide Poisoning

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Last Edited: 9/29/2010

Carbon Monoxide Poisoning: What is it?

Carbon monoxide (CO) poisoning occurs when the level of CO in the blood is higher than normal.  This results in reduced oxygen flow to tissues and organs and may cause permanent damage.

What is CO?

CO is an odorless, colorless, and tasteless gas.  It is produced by the incomplete burning of fuels, including oil, coal, wood, propane, and natural gas.  In-home appliances, such as furnaces and water heaters, are important sources of CO.

CO also exists in the environment as an air contaminant that is emitted from the exhaust of cars, boats, lawn mowers, and other internal combustion-powered equipment.  Although combustion engines are not usually the primary causes of CO poisoning, they are important contributors to air pollution.  Approximately 56% of all CO emissions nationwide come from motor vehicle exhaust.  This number can reach as high as 95% in urban areas.

Outdoor CO levels are highest during the colder months of the year when CO becomes trapped near the ground beneath a layer of warm air.  The Environmental Protection Agency (EPA) provides further information on CO as an air pollutant.


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What are common sources of CO?

Common sources of CO in and around the home include:
  •  Furnaces
  •  Water heaters
  •  Fire places
  •  Fuel-burning space heaters
  •  Cooking ranges
  •  Charcoal grills
  •  Portable generators
  •  Tobacco smoke

Common sources of CO outside of the home include:

  • Car and truck engines
  • Boats and other non-road equipment
  • Forest Fires

If equipment and appliances (such as those listed above) are not kept in working order and are not ventilated properly, CO emissions may build to dangerous levels.  This can lead to CO poisoning.


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What is CO poisoning?

When we breathe, our red blood cells pick up oxygen in the lungs.  The oxygen is then carried throughout the body to tissues and organs.  Red blood cells pick up CO more easily than they pick up oxygen.  So, if we breathe in large enough amounts of CO, the red blood cells will pick up CO instead of oxygen.  This will prevent enough oxygen from getting to our different body parts, which can then cause tissue damage.  In extreme cases, CO poisoning may be fatal.

Red Blood Cells and Carbon Monoxide

Image courtesy of the CDC

CO levels are measured in the blood in parts per million (ppm).  Levels above 70 ppm are considered toxic.  Sustained levels above 150 ppm are potentially deadly.


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What are the symptoms of CO poisoning?

Low to moderate CO poisoning is defined as having blood CO levels of 70 - 150 ppm.  The symptoms of low to moderate CO poisoning often resemble a flu-like illness.  They may include:

  • Headache
  • Nausea
  • Dizziness
  • Fatigue
  • Weakness
  • Shortness of breath

Severe CO poisoning is defined as having blood CO levels of greater than 150 ppm.  The symptoms of severe or prolonged CO poisoning may include:

  • Vomiting
  • Mental confusion
  • Loss of coordination
  • Loss of consciousness
  • Death

Recent research suggests that prolonged moderate to high CO exposure may be associated with an increased risk of heart disease (including heart attacks) and neurological problems (including brain damage).


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How is CO poisoning diagnosed?

The symptoms of CO poisoning often resemble those of a non-specific illness (such as the flu).  So, diagnosing CO poisoning may be difficult.   If CO poisoning is suspected, a blood sample may be taken by a medical professional in order to measure the levels of CO in the blood.


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