Causes and Risk Factors of Carbon Monoxide Poisoning

Learn to Recognize When CO Poisoning Happens

Carbon monoxide poisoning is caused by inhalation of carbon monoxide (CO) gas. The gas is odorless and colorless. It binds to hemoglobin, the iron-based protein in red blood cells that makes them red and carries oxygen. It only takes a small amount of carbon monoxide in the air to bump oxygen molecules off of the hemoglobin, and the amount usually comes accidentally from various sources of combustion.

carbon monoxide poisoning causes and risk factors
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Common Accidental Causes

Carbon monoxide is a product of combustion. Any combustion will give it off. Car exhaust is a well-known source, but so are wood fires and gas appliances—stoves, fireplaces, and water heaters, for example.

Poor ventilation in closed space leads to most carbon monoxide poisoning.

Some instances of accidental carbon monoxide poisoning come from inappropriate use of devices such as stoves, barbecues, or generators inside homes or buildings. However, most incidents are from equipment failure usually related to the ventilation of things like furnaces or motor vehicles.

Disaster Response/Recovery

Carbon monoxide is produced by many survival items used during natural disasters. It is common during the recovery period following a disaster to see increased emergency department visits for carbon monoxide poisoning.

The use of these devices should always include taking safety precautions to avoid exposure to CO gas.

Using survival items like generators or camp stoves is often done in less than ideal conditions. Often, the makeshift nature of the situation can make it easy to forget basic ventilation needs.

Intentional Poisoning

About 4% of all suicides in the United States use some form of gas. Of those, 73% involved carbon monoxide poisoning.

Alcohol is often a factor in intentional carbon monoxide poisoning cases.

The source of CO gas in the vast majority of all intentional carbon monoxide poisoning comes from motor vehicles or other combustion engines. Burning coal accounts for approximately 13%, a distant second.

Acute vs. Chronic Exposure

Carbon monoxide poisoning occurs from a buildup of CO gas in the bloodstream, measured by the amount of hemoglobin that is saturated with carbon monoxide molecules. The binding of hemoglobin and carbon monoxide creates what is known as carboxyhemoglobin. High levels of carboxyhemoglobin lead to tissue damage in the brain and heart from a combination of blocking oxygen and of causing inflammation.

Building up carboxyhemoglobin can happen slowly (chronic exposure) or quickly (acute exposure). Chronic exposure is often caused by a faulty or poorly ventilated appliance in the home that leads to the presence of low concentrations of carbon monoxide in the air. Think of this as a slowly leaking roof that eventually fills up a bucket placed below it.

Symptoms of chronic exposure often go unrecognized for long periods and carbon monoxide poisoning might not be reported.

Acute exposure typically comes from an accidental change in environment that leads to a high concentration of carbon monoxide in the air. In that case, the levels of carboxyhemoglobin rise quickly and symptoms are more pronounced. Acute exposure is more easily recognized and more often reported.


Proper use and maintenance of devices that release carbon monoxide is the best way to avoid accidental carbon monoxide poisoning. Additionally, recognizing the signs and symptoms of carbon monoxide poisoning when there is the possibility could save a life.

Since the symptoms of carbon monoxide poisoning are so vague, it is important to consider the possibility anytime there are gas appliances in the home or the possibility of CO coming in from a garage or nearby combustion engine. There are numerous examples of patients with carbon monoxide poisoning that occurred because of a car idling next to an open window.

Frequently Asked Questions

  • What's the most common way to be exposed to carbon monoxide?

    Indoors, the most common sources of carbon monoxide (CO) are unvented space heaters fueled by gas or kerosene, leaky chimneys, faulty furnaces, and gas stoves. Outdoors, you're most likely to encounter CO around cars, trucks, and other vehicles that burn fossil fuels.

  • How can you get carbon monoxide poisoning from a car?

    Carbon monoxide is produced when fuel does not burn completely. If you are in an enclosed space such as a garage when a car is started and allowed to run, CO can escape from the tailpipe and fill up the garage. For this reason, it is never safe to warm up a car while it's in a garage, even with the door open, or to burn anything indoors without proper ventilation. Even a cozy wood fire can cause CO poisoning.

  • How long does it take to get carbon monoxide out of your body?

    At least several hours of breathing fresh, clean air. To speed the elimination of CO from the body, an affected person can be given oxygen. In severe cases of CO poisoning, hyperbaric oxygen therapy (HBOT) may be used, which involves exposure to pure oxygen at an elevated pressure—1.5 to three times higher than normal. This speeds up the rate at which oxygen gets to damaged tissue.

9 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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  6. Iqbal S, Clower JH, Hernandez SA, Damon SA, Yip FY. A review of disaster-related carbon monoxide poisoning: surveillance, epidemiology, and opportunities for preventionAm J Public Health. 2012;102(10):1957-1963. doi:10.2105/AJPH.2012.300674

  7. United States Environmental Protection Agency. Basic information about carbon monoxide (CO) outdoor air pollution.

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  9. Johns Hopkins Medicine. Hyperbaric oxygen therapy.

Additional Reading

By Rod Brouhard, EMT-P
Rod Brouhard is an emergency medical technician paramedic (EMT-P), journalist, educator, and advocate for emergency medical service providers and patients.