Carbon Monoxide Poisoning

Carbon monoxide is a colorless, tasteless, odorless gas that results from incomplete burning of solid, liquid, and gaseous fuels. This gas can cause dizziness, nausea, coma * , or death if breathed in suffcient amounts.

A Close Call

The neighbors could set a clock by Dr. Smith's morning routine. He turned off the porch light at 6:00 a.m., picked up the newspaper from the driveway at 6:15, and took the dog for a walk at 6:30. One winter morning, Dr. Smith's next-door neighbor noticed that none of these activities had occurred. He knew the Smiths were home, but they did not answer the doorbell or the telephone.

The neighbor called the police, who broke into the house and found four unconscious people. The gas heater had shut off during the night and had been giving off carbon monoxide gas for many hours. The Smiths were rushed to the hospital and treated for carbon monoxide poisoning. Dr. Smith and his wife and children were lucky; they were found in time and recovered completely after several weeks.

What is Carbon Monoxide Poisoning?

Carbon monoxide (CO) is a chemical created when some fuels, such as coal and gasoline, are burned. CO is toxic because it reduces the amount of oxygen received by the body's cells. Red blood cells contain a protein called hemoglobin that carries oxygen to the body's cells. Hemoglobin in red blood cells binds with oxygen in the lungs and carries it to cells throughout the body where it is released. When a person inhales CO, the CO binds much more easily and tightly to hemoglobin than oxygen does, and it does not release well from hemoglobin. Thus, a person who breathes in CO has less and less hemoglobin available to carry oxygen. The amount of CO in the blood increases while the amount of oxygen decreases. When that happens, cells such as those of the heart, brain, and skeletal muscles become starved for oxygen and cannot operate normally. They undergo the cellular version of suffocation.

Acute CO Poisoning

Dr. Smith and his family suffered acute * CO poisoning, in which a large amount of CO was breathed at one time. This kind of poisoning can lead to death. It kills 25 to 40 percent of those exposed. In the first decade of the 21st century, an average of 430 deaths due to CO poisoning occurred in the United States each year. Of these, almost half were suicides and more than one-quarter came from fires. More than three-quarters of the deaths occurred from CO exposure at home. Survivors may feel symptoms for days, months, or years.

Chronic CO Poisoning

CO poisoning also can be chronic * . A small amount of CO inhaled continuously or frequently over a long period does not kill, but it does impair oxygen flow to the brain and may cause long-term nervous system problems, such as headaches, dizziness, weakness, sleepiness, nausea, and vomiting. Low-level chronic exposure to CO is especially serious for people with heart, lung, or circulatory problems and for infants and older adults. Developing fetuses also can be affected by CO inhaled by the mother.

Carbon Monoxide and the Environment

CO is one of the most prevalent poisons in the environment. It can get into buildings, homes, and vehicles in many ways. Sources of CO include car exhaust, malfunctioning or blocked gas or oil furnaces, generators, kerosene lamps, space heaters, improperly installed appliances, wood stoves, wood-burning fireplaces, and tobacco smoke. CO poisoning most often occurs during winter months, when people use heaters and fireplaces. Large fires, such as forest fires or building fires, also create carbon monoxide.

How Is CO Poisoning Treated?

A person with acute CO poisoning requires extra oxygen as soon as possible. The individual may be given pure oxygen to breathe. A hyperbaric oxygen chamber also may be used to treat CO poisoning. This is a large chamber that holds the patient and sometimes the medical team. The chamber is filled with 100 percent oxygen. (Normal air is 20.9 percent oxygen.) The pressure in the hyperbaric chamber is increased to three atmospheres (three times the pressure of the air near the Earth's surface, or the pressure the body feels about 90 feet under water). Pressure and pure oxygen help the oxygen molecules displace the CO attached to hemoglobin. Diagnosis and treatment of chronic CO poisoning may be more difficult because its symptoms are similar to many other conditions.

Can CO Poisoning Be Prevented?

CO poisoning is usually preventable. Basic safety guidelines include the following:

See also Environmental Diseases: Overview


Books and Articles

Estenson, Joseph. Carbon Monoxide—A Reference Guide, Washington, DC: Capitol Hill Press, 2015.

Stabile, J.R., et al. “Delayed Visual Disturbances in Carbon Monoxide Poisoning: Identification and Evaluation.” Undersea Hyperbaric Medicine 42 no. 4 (Jul-Aug 2015: 307-12).


Centers for Disease Control and Prevention. “Carbon Monoxide Poisoning.” (accessed March 18, 2016).

MedlinePlus. “Carbon Monoxide Poisoning.” U.S. National Library of Medicine. (accessed March 18, 2016).


Centers for Disease Control and Prevention. 1600 Clifton Road, Atlanta, GA 30333. Toll-free: 800-311-3435. Website: .

Environmental Protection Agency, Office of Radiation and Indoor Air, Indoor Environments Division. Pennsylvania Avenue, NW, Mail Code 6609, Washington, DC 20460. Telephone: 202-343-9370. Website:

United States Consumer Products Safety Commission. 4330 East West Highway, Bethesda, MD. 20814. Telephone: (301) 504-7923. Website:

* coma (KO-ma) is an unconscious state, like a very deep sleep. A person in a coma cannot be awakened, and cannot move, see, speak, or hear.

* acute describes an infection, illness, or other condition that comes on suddenly and usually does not last very long.

* chronic (KRAH-nik) lasting a long time or recurring frequently.

Disclaimer:   This information is not a tool for self-diagnosis or a substitute for professional care.

(MLA 8th Edition)