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Carbon Monoxide Poisoning


Gerald F. O’Malley

, DO, Grand Strand Regional Medical Center;

Rika O’Malley

, MD, Grand Strand Medical Center

Reviewed/Revised May 2022 | Modified Sep 2022

Carbon monoxide is a colorless, odorless gas that is produced when many materials are burned and can be toxic when breathed in large amounts

  • Carbon monoxide poisoning is common.

  • Symptoms may include headache, nausea, drowsiness, and confusion.

  • The diagnosis is based on blood tests.

  • Carbon monoxide detectors, adequate venting of furnaces and other sources of indoor combustion, and not allowing a car to run in an enclosed space (for example, a closed garage) help prevent carbon monoxide poisoning.

  • Treatment includes fresh air and high concentrations of oxygen, sometimes using a hyperbaric (high-pressure) oxygen chamber.

Inhaled carbon monoxide attaches to hemoglobin, the protein in red blood cells that gives blood its red color and enables it to carry oxygen. Carbon monoxide prevents the blood from carrying oxygen so the body's tissues do not get enough oxygen. Small amounts are not usually harmful, but poisoning occurs if levels of carbon monoxide in the blood become too high. Carbon monoxide is breathed out of the lungs and disappears from the blood after several hours.

Smoke from fires commonly contains carbon monoxide, particularly when combustion of fuels is incomplete. If improperly vented, automobiles, furnaces, hot water heaters, gas heaters, kerosene heaters, and stoves (including wood stoves and stoves with charcoal briquettes) can cause carbon monoxide poisoning. For example, when the exhaust pipe of a running car is blocked by piled-up snow or another object, carbon monoxide levels rise inside the car rapidly and can be fatal. Inhaling tobacco smoke produces carbon monoxide in the blood, but usually not enough to result in symptoms of poisoning.

Did You Know...

  • Carbon monoxide is one of the most common causes of poisoning deaths.

Symptoms of Carbon Monoxide Poisoning

Mild carbon monoxide poisoning causes headache, nausea, dizziness, difficulty concentrating, vomiting, drowsiness, and poor coordination. Most people who develop mild carbon monoxide poisoning recover quickly when moved into fresh air.

Moderate or severe carbon monoxide poisoning causes impaired judgment, confusion, unconsciousness, seizures, chest pain, shortness of breath, low blood pressure, and coma. Thus, many victims are not able to move themselves and must be rescued.

Severe carbon monoxide poisoning is often fatal. Rarely, weeks after apparent recovery from severe carbon monoxide poisoning, symptoms such as memory loss, poor coordination, movement disorders, depression, and psychosis (which are referred to as delayed neuropsychiatric symptoms) develop.

Carbon monoxide is dangerous because a person may not recognize drowsiness as a symptom of poisoning. Consequently, someone with mild poisoning can go to sleep and continue to breathe the carbon monoxide until severe poisoning or death occurs. Some people with long-standing, mild carbon monoxide poisoning caused by furnaces or heaters may mistake their symptoms for other conditions, such as the flu or other viral infections.

Diagnosis of Carbon Monoxide Poisoning

  • Blood test

Carbon monoxide poisoning is diagnosed by measuring the level of carbon monoxide in the blood.

Because symptoms can be vague and variable, mild carbon monoxide poisoning may be mistaken for the flu. If people from the same dwelling, particularly a heated dwelling, all experience vague flu-like symptoms at the same time, doctors may suspect carbon monoxide exposure as the cause.

Prevention of Carbon Monoxide Poisoning

To prevent poisoning, indoor sources of combustion, such as gas space heaters and wood stoves, require proper installation and ventilation. If such ventilation is impractical, an open window can limit carbon monoxide accumulation by allowing it to escape from the building. Exhaust pipes attached to furnaces and other heating appliances need periodic inspections for cracks and leaks.

Chemical detectors are available for the home that can sense carbon monoxide in the air and sound alarms when it is present. If carbon monoxide is suspected in a home, windows should be opened, and the home should be evacuated and evaluated for the source of the carbon monoxide. Constant monitoring with such detectors can identify carbon monoxide before poisoning develops. As with smoke detectors, carbon monoxide detectors are recommended for all homes.

Did You Know...

  • As with smoke detectors, carbon monoxide detectors are recommended for all homes.

Treatment of Carbon Monoxide Poisoning

  • Fresh air

  • Supplemental oxygen

  • Possibly hyperbaric oxygen

For mild carbon monoxide poisoning, fresh air may be all that is needed. To treat more severe poisoning, high concentrations of oxygen are given, usually through a face mask. Oxygen hastens the disappearance of carbon monoxide from the blood and relieves symptoms. The value of high-pressure oxygen treatment Recompression Therapy Recompression therapy involves giving 100% oxygen for several hours in a sealed chamber at high pressures (at least 1.9 atmospheres). (See also Overview of Diving Injuries.) Recompression therapy... read more (in a hyperbaric chamber) remains uncertain. Doctors typically consider hyperbaric oxygen treatment for people with moderate or severe poisoning and for pregnant women, even if the pregnant woman's blood level of carbon monoxide is not as highly elevated.

More Information

The following is an English-language resource that may be useful. Please note that THE MANUAL is not responsible for the content of this resource.

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