Carbon monoxide is an odorless, tasteless gas, but exposure can be fatal. Symptoms include headaches, dizziness, weakness, and nausea. Anyone with carbon monoxide poisoning needs urgent medical treatment.

Carbon monoxide (CO) is a byproduct of combustion. Common household items — such as gas fires, oil-burning furnaces, portable generators, and charcoal grills — put people at risk of exposure to this poison gas.

According to the Centers for Disease Control and Prevention (CDC), over 400 Americans die every year from accidental CO poisoning that does not result from fires. There are also more than 20,000 emergency room visits and over 4,000 hospitalizations.

In this article, we detail the symptoms, treatments, and causes of carbon monoxide poisoning.

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The person may feel like they have the flu but without a fever. If several people in the same building have the same symptoms, they may have CO poisoning.

The most common symptoms of CO poisoning are:

If the symptoms are mild, there is a high chance of a full recovery.

CO poisoning may affect people with heart-related or breathing problems more quickly. Pregnant people, babies, and small children are also more susceptible.

Pets, too, will react quickly to CO poisoning. If a family pet suddenly becomes ill or unexpectedly dies, the owners should rule out CO poisoning as one of the possible causes.

The first step is to move away from the possible CO gas source and contact medical services. A medical professional will be able to assess symptoms accurately.

If a person’s symptoms are severe, they may require hospitalization. Hospital treatments include the delivery of 100% oxygen through a mask.

This can speed up the production of oxygen-carrying proteins in red blood cells, known as oxyhemoglobin, which helps to replace CO-carrying hemoglobin, called carboxyhemoglobin.

If a medical professional suspects nerve damage or if exposure to CO has been extensive, they may recommend hyperbaric oxygen therapy (HBOT). This treatment floods the blood with pure oxygen to compensate for the lack of oxygen caused by CO gas poisoning.

HBOT may be necessary for people experiencing a loss or reduction of oxygen supply, a person in a coma, individuals with a history of loss of consciousness, those with an unusual ECG reading or reduced brain activity, and those who are pregnant.

According to a 2012 study, CO binds to hemoglobin over 220% more easily than oxygen does. Because CO more easily occupies the space where oxygen would bind, its presence means that less oxygen can enter the hemoglobin.

As a result, parts of the body will experience oxygen starvation, and the affected parts may die.

Short term effects

Following CO exposure, a person may notice that something is wrong, but they may not know where the symptoms are coming from.

Short-term effects of CO exposure can include:

  • headache
  • lethargy
  • coma
  • seizures

Short-term exposure to CO can also cause death in severe circumstances.

Long term effects

Typically, the longer an individual is exposed to CO, the more severe the symptoms will become.

CO poisoning can cause severe brain damage, and it may cause a progressive worsening of memory and concentration.

Heart damage, including coronary heart disease, can result from prolonged exposure. In severe cases, a person may also experience urinary or fecal incontinence.

Very rarely, CO poisoning can also cause Parkinsonism. This is not the same as Parkinson’s disease but can result in physical stiffness, slow movements, and shaking.

Household appliances — such as gas fires, boilers, central heating systems, water heaters, cookers, and open fires that use gas, oil, coal, and wood — may be possible sources of CO gas. Due to poor maintenance, ventilation, or other technical faults, they may produce the gas.

Typically, well-maintained household appliances should produce negligible quantities of CO gas. Using old appliances and not servicing them frequently leads to a higher risk of CO emission.

The following can all produce CO and potentially lead to CO poisoning:

  • Leaving a car in a closed garage with its engine running.
  • Burning charcoal in a poorly-ventilated environment.
  • The fumes from certain paint removers and cleaning fluids.

In addition, people should handle products that contain methylene chloride (dichloromethane) with care because methylene chloride turns into CO upon inhalation.

Every dwelling should have a carbon monoxide alarm. Some detectors have a digital readout, while others give out a loud, high-pitched sound when levels of CO pass a certain limit.

According to the United States Consumer Product Safety Commission, long-term exposure to 1 to 70 parts per million (ppm) of CO may not cause noticeable symptoms. However, some people with existing heart conditions may experience an increase in chest pain.

If CO levels increase and remain above 70 ppm they may cause noticeable symptoms, such as headache and fatigue. If they reach above 150 to 200 ppm, they may cause disorientation, unconsciousness, and death.

To diagnose CO poisoning, a medical professional will first assess a person’s symptoms. They may then request a blood test to detect unusual levels of carboxyhemoglobin.

For people who do not smoke, a carboxyhemoglobin level of 3–4% is outside normal limits, while this level is around 10% in people who do smoke. A reading of more than 20% in adults and 15% in children indicates severe exposure.

As part of an overall diagnosis, medical professionals may order an electrocardiogram (ECG) to check for ischemia, irregular heart rhythms, and assess overall heart function. Ischemia is a lack of blood supply to the heart, a condition that can be life threatening.

It is important to be aware of the dangers of CO poisoning.

The following can help to prevent leakage of CO gas:

  • Keep appliances in good working order, and use them safely.
  • Do not use gas ranges or ovens for heating.
  • Make sure all rooms are well ventilated and that vents are not blocked. Be especially careful in well-insulated environments.
  • Ensure chimneys and flues are clear of obstruction and providing adequate ventilation.
  • Be careful when using gas-powered tools and equipment inside rooms.
  • Wear a mask when using products that contain methylene chloride.
  • Do not leave a gasoline-powered motor — such as a motorbike, car, or lawn mower — running in a garage.
  • Do not use charcoal on an indoor barbecue.
  • Service the exhaust pipe in a motor vehicle every year.
  • If the tailgate of a vehicle is open and the engine is running, open the doors and windows too.

CO is an odorless, tasteless gas. However, exposure to it in high amounts or over prolonged periods can result in poisoning.

The most common symptom of CO poisoning is a tension-like headache. Severe exposure can result in brain and heart damage and can be fatal.

The first line of treatment for CO poisoning is removing the affected person from the area of exposure. Medical professionals may wish to administer 100% oxygen via a mask or recommend HBOT.

Faulty gas appliances, motor vehicles, and some cleaning products can lead to CO poisoning. Ensuring that any such items are in good working order and installing CO alarms throughout indoor spaces can help prevent CO poisoning.