Carbon Monoxide Poisoning



  • Carbon monoxide (CO) is an odorless gas produced via incomplete combustion of carbonaceous fuels.
  • CO poisoning occurs when carboxyhemoglobin and CO accumulation leads to impaired physiologic function.


CO poisoning is a leading cause of death by poisoning within the United States.


  • >14,000 CO exposures were reported to the American Association of Poison Control Centers in 2015, with ~1/3 of such exposures occurring in children.
  • There are >400 deaths per year in the United States.
  • Seasonal cold weather and other natural disaster events lead to increases in incidence of exposure.

General Prevention

  • Furnaces should receive regular maintenance by skilled technicians.
  • Automobiles, gas-powered machinery, and nonelectrical space heaters should only be used with proper ventilation.
  • CO detectors should be installed within living spaces.


  • On inhalation, some CO binds to hemoglobin to form carboxyhemoglobin.
  • Carboxyhemoglobin does not carry oxygen.
  • Carboxyhemoglobin produces an allosteric leftward shift of the oxyhemoglobin dissociation curve.
  • Carboxyhemoglobin elimination half-life
    • ~4 hours in room air
    • 1 to 2 hours in 100% oxygen
    • 20 minutes in 100% oxygen at 3 atmospheres
  • CO interacts with cellular proteins, leading to impaired mitochondrial function.
  • CO is a source of oxidative stress and poisoning may begin a cascade of inflammatory vasculitis within the CNS and heart.


  • Common sources of CO exposure include the following:
    • Automobile or boat exhaust
    • Smoke inhalation from house fires
    • Oil, gas, or kerosene space heaters or cooking stoves
    • Portable electricity generators and construction equipment
    • Faulty home furnaces
  • The solvent methylene chloride is metabolized to CO by the liver after ingestion, inhalation, or dermal absorption.
  • CO is a component of cigarette smoke and environmental air pollution.
  • CO is a naturally occurring by-product of the heme biosynthesis pathway.

Commonly Associated Conditions

Victims of house fires may suffer from thermal injury and/or cyanide poisoning.

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