What Is Carbon Monoxide Poisoning?

Learn about the symptoms, causes, and how it’s treated

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Carbon monoxide poisoning occurs when you breathe in too much carbon monoxide (CO), a colorless, odorless gas produced by the combustion of fuel.

Symptoms of carbon monoxide poisoning include headaches, dizziness, weakness, vomiting, chest pain, and confusion.

Excessive exposure to CO can lead to severe heartbeat irregularities, seizures, unconsciousness, and even death.

Carbon monoxide poisoning is relatively common in the U.S., with around 50,000 emergency room admissions each year, according to the Centers for Disease Control and Prevention (CDC). It can be largely avoided with inexpensive yet effective carbon monoxide alarms installed in the home.

This article discusses the symptoms of carbon monoxide poisoning and how it’s diagnosed. It also discusses how it’s treated and ways to prevent it.

What Is Carbon Monoxide Poisoning?
Verywell / Emily Roberts

Carbon Monoxide Poisoning Symptoms

With carbon monoxide poisoning, symptoms involve parts of the body that require oxygen most, namely the heart and the central nervous system (CNS). Initial carbon monoxide poisoning symptoms typically include nausea, malaise, fatigue, and a dull but persistent headache.

As the CO continues to build up in the bloodstream, the depletion of oxygen in tissues will trigger an ever-worsening cascade of symptoms, including:

  • Dizziness
  • Shortness of breath (dyspnea)
  • Chest pain
  • Nausea and vomiting
  • Confusion or delirium
  • Irregular heart rate (arrhythmia)
  • Heart rate faster (tachycardia) or slower (bradycardia) than usual
  • Stroke
  • Unconsciousness
  • Coma
  • An unsteady (ataxic) gait
  • Changes in rate of breathing
  • Seizures

Death may occur as a result of effects on the heart or respiration, including respiratory arrest.

Even after a person has been treated for CO poisoning, there is a risk of long-term and even permanent neurological complications, including memory problems, irritability, depression, speech disturbances, partial vision loss, dementia, and Parkinson’s disease-like symptoms.

How Long Does Carbon Monoxide Poisoning Take to Show Symptoms?

Carbon monoxide poisoning can be fatal within minutes. Children, pregnant women, older adults, and/or those with chronic illness may be affected more severely and rapidly. People who are sleeping or intoxicated can die from carbon monoxide poisoning before they ever become aware of their symptoms.


Carbon monoxide easily enters the body through the lungs. As CO is transferred into the bloodstream, it will preferentially bind to hemoglobin, the protein in red blood cells responsible for transporting oxygen throughout the body. By doing so, CO prevents oxygen from getting to the tissues and cells that need it to survive.

Carbon monoxide is a natural byproduct of combustion. Most cases of poisoning result from the inhalation of the gas as it quickly accumulates in an enclosed space (usually due to faulty ventilation).

Common Sources of CO Include:

  • Wood-burning stoves
  • House fires
  • Vehicle exhaust fumes
  • Gas or propane stoves and grills
  • Charcoal grills and hibachis
  • Unvented propane, kerosene, or gas space heaters 
  • Gas-powered electrical generators
  • Gas clothes dryers

Riding in the back of a pickup truck is a common cause of carbon monoxide poisoning in children. Similar, idling your car in winter can poison passengers if the exhaust pipe is blocked with snow. In fact, any perforation in the exhaust manifold of a car or boat can allow CO to flood the interior.

Carbon monoxide poisoning may also occur intentionally. According to research published in the Annals of the American Thoracic Society, 831 suicides in 2014 were a result of carbon monoxide poisoning, either from a vehicle’s exhaust fumes or a combustible fuel source in the house.

With that being said, suicide by this method has been on the decline since 1975 when federal law dictated the installation of catalytic converters in all motor vehicles.

carbon monoxide poisoning causes and risk factors

© Verywell, 2018 


Unless carbon monoxide is recognized as the cause of your symptoms, it may be misdiagnosed when you first arrive at the emergency room. It is important, therefore, to advise the ER doctor of your suspicions if you believe CO is involved. 

The diagnosis is relatively straightforward. It involves a non-invasive probe, called a CO-oximeter, which measures CO compounds in the blood. The device can be placed on your finger, toe, or other parts of the body.

The oximeter contains two diodes that emit light beams of different wavelengths. The amount of light absorbed by tissue can tell doctors how much carboxyhemoglobin (the compound created by the binding CO and hemoglobin) is in the blood.

Under normal circumstances, you would have less than 5% carboxyhemoglobin compared to free hemoglobin. Generally, poisoning occurs if the level is above 10%. Death can occur at levels over 25%.

Regular pulse oximeters are not useful as they are not able to distinguish between carboxyhemoglobin and oxyhemoglobin (the compound created by the binding of oxygen and hemoglobin).


If carbon monoxide poisoning is suspected, the first course of action is to remove yourself and others from the source of the CO. Even if symptoms are mild, emergency medical treatment should be sought.

Treatment may involve the administration of pressurized oxygen through a non-circulating mask. By increasing oxygen levels in the blood, CO can be cleared from the body about five times faster than on its own. The oxygenation can actually break up carboxyhemoglobin and release hemoglobin back into the bloodstream.

In severe cases, a hyperbaric chamber may be used, which can deliver 100% oxygen in a high-pressure environment. Hyperbaric oxygen clears CO from the blood nearly four times faster than oxygen delivered at normal atmospheric pressure. It also allows oxygen to partially bypass hemoglobin and be delivered directly to tissue.

In addition to oxygen, other treatments may be required, including:

  • Cardiac life support to treat dangerous arrhythmias
  • Intravenous fluids to treat hypotension
  • Injection of hydroxocobalamin to treat metabolic acidosis (the buildup of acids in the blood due to suppressed kidney function)
  • An anticonvulsant such as Valium (diazepam) to treat seizures


The most effective means of prevention in the home is a carbon monoxide alarm. They are readily available online and in most hardware stores, ranging in price from $20 for a plug-in monitor to $80 for a combination CO/smoke alarm.

The U.S. Consumer Product Safety Commission (CPSC) recommends that every home has at least one CO detector and preferably one for each floor.

Among the other recommended safety tips:

  • Make sure your gas appliances are properly vented.
  • Have your heating system, water heater, and any gas- or coal-burning appliance serviced by a technician every year.
  • Never use an electrical generator inside the home, garage, or less than 20 feet from any window, door, or vent.
  • Have your chimney checked and cleaned annually.
  • Open the fireplace damper before lighting a fire and well after it has been extinguished.
  • Never use a gas oven to heat your home.
  • Never let a car idle in the garage.
  • Know the symptoms of carbon monoxide poisoning.

A Word From Verywell 

If your carbon monoxide alarm goes off, never assume that it’s a false alarm even if you have no symptoms. Because CO is tasteless and odorless, you need to assume that the risk is real and to take the appropriate action.

First and foremost, do not look for the source of gas. The CPSC instead recommends that you:

  • Immediately move outside into the fresh air.
  • Call the fire department, emergency services, or 911.
  • Do a head count to check to ensure everyone is accounted for.
  • Do not re-enter the building until the emergency responders give you permission to do so.

Frequently Asked Questions

  • Is there an app to test for carbon monoxide symptoms?

    While there are phone apps that claim to detect carbon monoxide, they may not be the most reliable. A safer option is to install a “smart detector” in your home, like those made by Onelink or Nest. These detectors can synch with your smartphone, enabling you to receive notifications if they detect carbon monoxide, if your detector’s batteries get low, and more.

  • Does carbon monoxide poisoning cause hallucinations?

    Exposure to very high levels of carbon monoxide may induce hallucinations.

  • What are carbon monoxide poisoning symptoms sometimes mistaken for?

    Early symptoms of carbon monoxide poisoning are often described as flu-like. This includes symptoms like headache, dizziness, weakness, upset stomach, and chest pain.

14 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.
  1. Centers for Disease Control and Prevention. Carbon monoxide (CO) poisoning prevention.

  2. Kinoshita H, Türkan H, Vucinic S, et al. Carbon monoxide poisoning. Toxicol Rep. 2020 Jan;7(1):169-173. doi:10.1016/j.toxrep.2020.01.005

  3. Hampson NB, Piantadosi CA, Thom SR, Weaver LK. Practice recommendations in the diagnosis, management, and prevention of carbon monoxide poisoning. Am J Respir Crit Care Med. 2012;186(11):1095-1101. doi:10.1164/rccm.201207-1284CI

  4. Kara H, Bayir A, Ak A, Degirmenci S. Cerebrovascular ischaemia after carbon monoxide intoxication. Singapore Med J. 2015;56(2):e26-e28. doi:10.11622/smedj.2015030

  5. Chi YJ, Pan HY, Cheng FJ, Chang YI, Chuang PC. Experience of carbon monoxide poisoning and the outcome predicting score: a multicenter retrospective study. Am J Emerg Med. 2022;58:73-78. doi:10.1016/j.ajem.2022.05.012

  6. Rose JJ, Wang L, Xu Q, et al. Carbon monoxide poisoning: pathogenesis, management, and future directions of therapy. Am J Respir Crit Care Med. 2017;195(5):596-606. doi:10.1164/rccm.201606-1275CI

  7. Martani L, Giovanniello A, Bosco G, et al. Delayed neurological sequelae successfully treated with adjuvant, prolonged hyperbaric oxygen therapy: review and case report. Int J Environ Res Public Health. 2022;19(9):5300. doi:10.3390/ijerph19095300

  8. Liu J, Si Z, Liu J, et al. Clinical and imaging prognosis in patients with delayed encephalopathy after acute carbon monoxide poisoning. Behav Neurol. 2020;2020:1719360. doi:10.1155/2020/1719360

  9. Hampson NB. U.S. mortality due to carbon monoxide poisoning, 1999–2014. accidental and intentional deaths. Ann Am Thorac Soc. 2016;13(10):1768-1774. doi:10.1513/AnnalsATS.201604-318OC 

  10. Hampson NB. Carboxyhemoglobin: a primer for clinicians. Undersea Hyperb Med. 2018;45(2):165-171. doi:10.22462/03.04.2018.3

  11. Eichhorn L, Thudium M, Jüttner B. The diagnosis and treatment of carbon monoxide poisoningDtsch Arztebl Int. 2018;115(51-52):863-870. doi:10.3238/arztebl.2018.0863

  12. Rose JJ, Nolley E, Gladwin MT. A 53-year-old woman with severe carbon monoxide poisoning. Ann Am Thorac Soc. 2017;14(9):1475-1478. doi:10.1513/AnnalsATS.201701-002CC

  13. Manning EP. Central nervous system oxygen toxicity and hyperbaric oxygen seizures. Aerosp Med Hum Perform. 2016;87(5):477-486. doi:10.3357/AMHP.4463.2016

  14. Consumer Product Safety Commission. Carbon monoxide fact sheet.

Rod Brouhard, EMT-P

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.