Carbon Monoxide Poisoning

Topic Overview

What is carbon monoxide poisoning?

Carbon monoxide poisoning happens when you breathe too much carbon monoxide. Carbon monoxide is a gas produced by burning any type of fuel-gas, oil, kerosene, wood, or charcoal. What makes carbon monoxide so dangerous is that when you breathe it, it replaces the oxygen in your blood . Without oxygen, cells throughout the body die, and the organs stop working.

You can't see, smell, or taste carbon monoxide. But if you breathe too much of it, it can become deadly within minutes. So it's very important to know the signs of carbon monoxide poisoning, what to do if you have the symptoms, and how to keep it from happening.

What causes carbon monoxide poisoning?

Carbon monoxide can come from any source that burns fuel. Cars, fireplaces, powerboats, woodstoves, kerosene space heaters, charcoal grills, and gas appliances such as water heaters, ovens, and dryers all produce carbon monoxide. Usually they cause no problems. Trouble comes when:

• Cars, trucks, or other engines are left running in enclosed spaces, such as garages. Carbon monoxide can build up in a garage and leak back into the house. Even sitting in an idling car in an open garage or swimming behind an idling boat can be dangerous.
• Fuel-burning appliances are not installed or used properly. Dangerous levels of carbon monoxide can build up inside houses and other buildings.
• Fuel-burning heating systems and appliances are used during cold weather, when doors and windows are closed. Chimneys in older buildings become blocked and release fumes into the homes or offices. Newer houses that are well insulated and tightly sealed can trap carbon monoxide inside living areas.

What are the symptoms?

Early symptoms of carbon monoxide poisoning include:

• Headache.
• Dizziness.
• Nausea.

If you have these symptoms and there is a chance they could be caused by carbon monoxide poisoning, leave the area right away and call 911 or go to the emergency room. If you keep breathing the fumes, you may pass out and die.

Carbon monoxide poisoning can occur suddenly or over a long period of time. Breathing low levels of carbon monoxide over a long period can cause severe heart problems and brain damage. See a doctor if:

• You often are short of breath and have mild nausea and headaches when you are indoors.
• You feel better when you leave the building and worse when you return.
• Other people you work or live with have the same symptoms you do.

How is carbon monoxide poisoning diagnosed?

If your doctor suspects carbon monoxide poisoning, he or she can order a blood test that measures the amount of carbon monoxide in your blood. You may have other blood tests to check your overall health and to look for problems caused by carbon monoxide poisoning.

It can be hard to know if you have carbon monoxide poisoning. The same symptoms can be caused by flu or other problems. In the winter months, doctors may suspect carbon monoxide poisoning in people who complain of severe headache, nausea, or dizziness. This is especially true if other household members or coworkers have similar symptoms.

How is it treated?

The best treatment is oxygen therapy. Breathing pure oxygen can bring the oxygen level in the blood back to normal. There are two kinds of oxygen therapy:

• 100% oxygen therapy, in which you breathe oxygen through a tight-fitting mask. This is the most common type of oxygen therapy.
• Hyperbaric oxygen therapy. For this treatment, you lie in a full-body chamber that delivers oxygen under high pressure. This quickly reduces carbon monoxide levels in the blood.

With quick treatment, most people recover within a few days. But long-term problems can show up later. It is important to tell your doctor about any changes in vision, coordination, or behavior that occur in the weeks after treatment.

How can you prevent carbon monoxide poisoning?

Many people die every year from accidental carbon monoxide poisoning. There are some important steps you can take to reduce your risk.

• Have all fuel-burning appliances (such as oil or gas heaters, stoves, water heaters, and space heaters, fireplaces, and woodstoves) inspected each year.
• Check chimneys, flues, and vents regularly to make sure they are in good shape, properly connected, and not blocked.
• See a doctor right away if you think you have symptoms of carbon monoxide poisoning, especially if more than one person has the same symptoms.

Know how to avoid carbon monoxide poisoning when you operate a vehicle:

• Do not leave your car running in the garage, even if the garage door is open.
• Do not ride in the back of a pickup truck with a camper shell.
• Do not swim behind an idling boat.

Be safe when you use fuel-burning tools or appliances:

• Never use a kerosene or propane heater in an enclosed area, such as a camper, motor home, trailer, or tent.
• Never use a gas or charcoal grill indoors.
• Never use a gas oven to heat your home.
• Do not close a fireplace or stove damper before the fire is completely out.
• Do not use gas-powered generators, lawn equipment, or engines in enclosed areas.

Consider putting carbon monoxide detectors in your home near sleeping areas. Look for ones endorsed by Underwriters Laboratory (UL). If you install carbon monoxide detectors:

• Be sure to follow the directions carefully, and know what to do if the alarm sounds.
• Understand that carbon monoxide detectors are a backup safety measure. They do not replace the need to check appliances regularly and use them safely.

Frequently Asked Questions

Cause

Carbon monoxide poisoning is caused by inhaling carbon monoxide, a colorless, odorless, and tasteless gas produced by the incomplete burning of fuels. It may build up in enclosed or semi-enclosed areas such as cars, houses, or buildings. If too much carbon monoxide builds up, it can become deadly.

Common sources of carbon monoxide include:

• Faulty indoor heating systems (such as gas, wood-burning, or coal-burning stoves or furnaces).
• Car exhaust.
• Houseboat generators.
• Cooking appliances.
• Propane-powered forklifts, ice-resurfacing machines, and other work equipment.
• Smoke from a burning vehicle or building.

Injuries and deaths from carbon monoxide poisoning in the United States have declined significantly since the Clean Air Act was passed by Congress in 1970. But carbon monoxide remains one of the leading causes of poisoning death in the U.S. More than 1,700 suicides and 500 accidental deaths every year are from carbon monoxide poisoning.¹

Symptoms

Symptoms of carbon monoxide poisoning range from mild flu-like symptoms (such as a headache or stomachache without fever) to severe signs of heart and brain damage. Prolonged exposure to low levels of carbon monoxide over many days may result in death.

People respond differently to the same level of carbon monoxide. Because of this, carbon monoxide poisoning can range from mild to severe in different people with the same level of exposure.

A person who has mild symptoms usually does not even suspect carbon monoxide poisoning. Early symptoms can mimic the flu or a number of other conditions with similar symptoms, which can make it difficult for a doctor to diagnose. It is possible that a person with more severe poisoning may not even be aware of the seriousness of the condition because the exposure to carbon monoxide may cause fatigue and confusion. If a person has symptoms of carbon monoxide poisoning or if carbon monoxide poisoning is suspected, first get the person out of the polluted area, and then call 911 .

Symptoms of carbon monoxide poisoning are often similar to symptoms of other illnesses. These symptoms include:²

• Headache.
• Nausea, vomiting (often seen in children).
• Dizziness.
• Fatigue.

More severe symptoms may include:

• Confusion, drowsiness.
• Rapid breathing or pulse rate.
• Vision problems.
• Chest pain.
• Convulsions, seizures.
• Loss of consciousness.

Symptoms of carbon monoxide poisoning change with different blood concentrations of carboxyhemoglobin (hemoglobin that has bonded with carbon monoxide instead of oxygen).

Some situations may provide clues to carbon monoxide exposure. For example, if a family or group of people who live or work in the same building complain of headaches or flu-like symptoms, these symptoms may be caused by high levels of carbon monoxide. Also, family pets living in the home may become sick, which can be another clue to diagnosing carbon monoxide poisoning. In the winter, unexplained headaches, nausea, or dizziness may be caused by heating systems that are not working correctly and are causing a buildup of carbon monoxide.

Delayed symptoms or long-term adverse effects of carbon monoxide poisoning can occur days or weeks after poisoning. The delayed symptoms or effects may include memory loss, changes in personality, disorientation, impaired reasoning ability, and behavioral or learning difficulties.³

What Happens

Carbon monoxide poisoning occurs as carbon monoxide mixes and binds with hemoglobin in the blood to form carboxyhemoglobin (COHb). When carbon monoxide binds to hemoglobin , less oxygen gets transported to body tissues and vital organs such as the brain and heart. The bond between carbon monoxide and hemoglobin is approximately 250 times stronger than the bond between oxygen and hemoglobin.²

Several factors determine how carbon monoxide poisoning can affect you, including:³

• The amount of ventilation in the area where carbon monoxide is present.
• The amount of carbon monoxide inhaled.
• The length of time you are exposed to carbon monoxide.
• Your age. Infants, small children, and older adults are more easily affected and may have more severe symptoms.
• Your general health. People with other illnesses, such as heart disease, are more easily affected and may have more severe symptoms.
• The amount of carbon monoxide already in the blood of a person who smokes tobacco. Smokers already have some carbon monoxide in their blood and may have more severe symptoms.
• Altitude. The higher the altitude, the less oxygen is present in the air to compete with the carbon monoxide.

Symptoms of carbon monoxide poisoning change at different concentrations of carboxyhemoglobin in the blood .

If a woman is pregnant, the fetus is at high risk for developing carbon monoxide poisoning. It takes longer for carbon monoxide to be eliminated from the fetus's blood than from the mother's blood.³

Carbon monoxide poisoning can occur suddenly (inhaling a large amount of carbon monoxide over a short period of time), or it can occur slowly (inhaling a small amount of carbon monoxide over a long period of time).

• Death from carbon monoxide poisoning can occur within 10 minutes at very high concentrations.
• A person with mild symptoms of carbon monoxide poisoning may actually be severely poisoned.
• A person may have a delayed reaction to carbon monoxide poisoning, with symptoms occurring after exposure.
• A person who survives a severe case of carbon monoxide poisoning may develop permanent memory loss or brain damage.

There may be long-term effects of carbon monoxide poisoning, with symptoms that usually develop 2 to 40 days after exposure. These long-term symptoms can occur even if you were treated. Symptoms may include memory loss, changes in personality, disorientation, impaired reasoning ability, and behavioral and learning difficulties.

A study was done that looked at one long-term effect of carbon monoxide poisoning. The study found that people who had damage to the heart from moderate to severe carbon monoxide poisoning were more likely to die at a younger age than people who did not have damage to the heart from the poisoning.⁴

What Increases Your Risk

Most risk factors for carbon monoxide poisoning are ones that you can control and change. For example, to prevent the buildup of carbon monoxide in a home:

• Indoor heating systems and chimneys should be inspected yearly and repaired as needed.
• Have all internal appliances (such as stoves or furnaces) repaired right away if you suspect they may be malfunctioning.
• Have exhaust systems in your vehicle and home inspected and repaired on a regular basis.
• Do not leave vehicles running in an enclosed or semi-enclosed area, such as a garage.

You may also be exposed to carbon monoxide in situations that you cannot control, including:

• At your workplace, such as in warehouses where propane-powered forklifts are used, in steel foundries, or in pulp paper mills.
• During a fire (such as in a building, a boat, or a plane).

Your risk of being exposed to carbon monoxide is increased if you notice signs of faulty heating systems or appliances at your home or business. These signs may include:

• A missing or poorly fitted furnace panel.
• Loose bricks or a disconnected vent around the chimney.
• Soot, rust, or water streaks down a chimney, roof vent, furnace, or appliance.

When To Call a Doctor

Call 911 or other emergency services immediately if:

• You have symptoms of carbon monoxide poisoning, such as a headache, nausea, or dizziness, and carbon monoxide poisoning is suspected.
• A person has symptoms of carbon monoxide poisoning and appears to be very confused or disoriented or complains of chest pain. Leave the area of exposure before calling.
• A person is found unconscious after exposure to carbon monoxide. Take him or her out of the house, building, vehicle, or area where the gas is present.

Call your doctor if:

• You have any changes in vision, coordination, or behavior in the weeks after treatment for carbon monoxide poisoning.

What to do if your carbon monoxide detector sounds the alarm

Tell everyone in the house or building to get out. Call the fire department or your local utility company from a nearby phone.

The fire department or utility company can check the carbon monoxide levels in the house or building and identify any problem. If high levels of carbon monoxide are found in the building, call and discuss the situation with your doctor.

Watchful Waiting

Watchful waiting is not appropriate if carbon monoxide poisoning is suspected. Call 911 or your doctor.

Who To See

The following health professionals can evaluate symptoms of carbon monoxide poisoning:

• Emergency medical technician (EMT) who responds to 911 calls
• Emergency medicine specialist
• Critical care specialist
• Hyperbaric-trained physician
• Family medicine doctor
• Internist
• Nurse practitioner
• Physician assistant

The following health professionals can evaluate delayed or long-term symptoms of carbon monoxide poisoning:

• Neurologist
• Psychologist

To prepare for your appointment, see the topic Making the Most of Your Appointment.

Exams and Tests

If you are exposed to carbon monoxide or if carbon monoxide poisoning is suspected, your doctor will ask questions about your medical history. Questions may include how long symptoms have been present, what the source of possible exposure to carbon monoxide is, how many other people (family members or coworkers) have the same symptoms, and what home heating and cooking appliances have been used. With this information, your doctor may decide that a test for carbon monoxide is necessary.

The standard test for carbon monoxide measures the amount of hemoglobin that has bonded with carbon monoxide. This amount is also called the carboxyhemoglobin (COHb) level.

Testing should never delay treatment. Treatment should be started as soon as possible.

Other tests such as an arterial blood gas (ABG) and a complete blood count (CBC) also may be done if you have or are suspected of having carbon monoxide poisoning. These tests may be done to evaluate your overall health or to identify problems caused by carbon monoxide poisoning.

A handheld breath analyzer measures how much carbon monoxide is in the air you exhale. This test measures high levels of the gas but may not be reliable in detecting low levels.

Other tests

Questionnaires and other tests may be used to detect subtle changes in your ability to think clearly, if carbon monoxide poisoning is suspected. They also may be used to determine what other treatment is needed.

If you do have carbon monoxide poisoning, you will probably have tests to check for heart damage, such as ECG and cardiac enzyme studies.

Early Detection

There is no routine screening for carbon monoxide poisoning. If carbon monoxide poisoning is suspected, further tests will be done.

In the winter months, carbon monoxide poisoning may be suspected in people who go to the emergency room with symptoms of a severe headache, nausea, or dizziness. Information about a person's home, workplace, and any illness of family members and coworkers is often gathered to determine whether a test for carbon monoxide should be done.

Treatment Overview

The goal of treatment for carbon monoxide poisoning is to remove carbon monoxide from the hemoglobin in your blood and bring the oxygen level in your blood back to normal.

For the immediate treatment of carbon monoxide poisoning, it is important that you remove yourself from the area where the gas may be present. If carbon monoxide poisoning is known or suspected, get out of the building or car where the carbon monoxide is present.

After you are taken to the hospital, you may be given oxygen therapy. The most common type of oxygen therapy, called 100% oxygen therapy, involves breathing oxygen through a tight-fitting mask. If you have severe carbon monoxide poisoning and can't breathe on your own, a breathing machine may be used to help you breathe and to provide extra oxygen. In some cases, a person may receive hyperbaric oxygen therapy. During this treatment, you are put into a full-body chamber that uses oxygen under pressure (hyperbaric chamber) to remove the carbon monoxide faster.

Several factors are considered when treating carbon monoxide poisoning. Tests are done to find out the amount of carbon monoxide in the blood. Infants, small children, older adults, and people with health problems are more severely affected by carbon monoxide in the blood. Treatment usually includes oxygen therapy to treat severe symptoms and to lower carbon monoxide levels in the blood as quickly as possible.

If treatment is timely, most people are able to recover from carbon monoxide poisoning. If it is not treated, severe carbon monoxide poisoning can lead to heart or brain damage or death. Even after treatment, a person who survives a severe case of carbon monoxide poisoning may have permanent memory loss or brain damage. But most people who are critically injured or who die from carbon monoxide poisoning never received treatment. It is especially important to be aware of the warning signs and to seek immediate treatment if carbon monoxide poisoning is suspected. For more information, see the Symptoms section of this topic.

What To Think About

• Oxygen therapy should not be delayed while tests are being done.
• During the weeks following treatment, any changes in vision, coordination, or behavior should be reported to your doctor.
• If a pregnant woman has carbon monoxide poisoning, treatment must be continued even after carbon monoxide is no longer found in her blood, because there still may be carbon monoxide in the blood of the fetus.

Prevention

Steps to prevent carbon monoxide poisoning include the following:

• Purchase and install a carbon monoxide detector on each level of your home and near sleeping areas. Detectors that have been verified by Underwriters Laboratory (UL) and have been manufactured after October 1995 conform to minimum alarm requirements. Those marked UL 2034 or IAS 6-96 have met the U.S. Consumer Product Safety Commission guidelines. Follow the directions for installing and using the detector carefully. Be prepared by knowing what to do if the detector alarm sounds-tell everyone in the house or building to get out, and call the fire department or your local utility company from a nearby phone.
• Even if you are using a carbon monoxide detector, have your heating system inspected each year.
• Don't ignore possible symptoms of carbon monoxide poisoning, such as headaches, nausea, and dizziness, especially if more than one person in your home or workplace has these symptoms.

Heat sources

• Have your heating appliances, chimneys, and vents inspected each year. All appliances should be working and vented properly to allow gas to escape from enclosed areas.
• Look at appliances, chimneys, and vents for visible soot, rust, stains, blockage, or corrosion.
• Don't use kerosene or propane heaters in an enclosed area such as a recreational vehicle, camper, motor home, trailer, or tent.
• Don't use a kitchen oven, especially a gas oven, to heat your home.
• Don't close the fireplace or wood/pellet stove damper before the fire is completely out.

Car exhaust

• Don't sit in a parked car with the windows closed and the engine running.
• Don't run the car engine in an enclosed or semi-enclosed area, such as a garage, even if the garage door is open.
• Don't ride in the back of a pickup truck with a camper shell.

Cooking

Don't burn charcoal or use a charcoal or propane grill indoors or in a recreational vehicle, camper, motor home, trailer, or tent.

Other sources

• Don't place outdoor power generators or pressure washers near windows or doors of your home.
• Don't smoke cigarettes or be near someone who is smoking in a poorly ventilated room.
• Don't use paint remover that contains methylene chloride. (Methylene chloride converts to carbon monoxide in the body.)

For more information, see how to monitor household carbon monoxide levels.

Home Treatment

Do not try to treat symptoms at home if carbon monoxide poisoning is suspected. Call 911 or your doctor.

Medications

There is no medication treatment for carbon monoxide poisoning.

Surgery

There is no surgical treatment for carbon monoxide poisoning.

Other Treatment

Oxygen therapy is the standard treatment for carbon monoxide poisoning. The purpose of oxygen therapy is to bring the oxygen level in the blood back to normal. Oxygen therapy replaces the carbon monoxide in the blood with oxygen.

Other Treatment Choices

Two types of oxygen therapy are used:

• 100% oxygen therapy. 100% oxygen therapy is the most common treatment for carbon monoxide poisoning. For 100% oxygen therapy, you breathe pure oxygen through a tight-fitting mask or, in some cases, with the assistance of mechanical ventilation (a tube down your windpipe). Oxygen therapy reduces the amount of carbon monoxide in the blood. Usually there are no risks with the short-term use of 100% oxygen therapy. But people who have chronic obstructive pulmonary disease (COPD) may have trouble breathing if they are given too much oxygen.
• Hyperbaric oxygen therapy. Hyperbaric oxygen therapy involves being enclosed in a full-body chamber while pure oxygen is pumped in under high pressure. This helps reduce carbon monoxide levels in the blood quickly and restores the oxygen-carrying capacity of the blood to normal. Hyperbaric chambers deliver oxygen at higher pressures than is otherwise possible. This treatment is used in moderate to severe cases of poisoning because it usually works faster than 100% oxygen therapy. One study concluded that three hyperbaric oxygen treatments within a 24-hour period may reduce the risk of cognitive problems, such as lasting damage to memory, attention, and concentration.⁵

The decision about whether to use hyperbaric oxygen therapy is made on a case-by-case basis, depending on the person and on how bad the carbon monoxide poisoning is. Hyperbaric oxygen therapy is used most often to treat severe cases of carbon monoxide poisoning, including people who are or have been unconscious because of carbon monoxide poisoning, people who have severe symptoms such as confusion, and pregnant women who have had significant exposure to carbon monoxide.

What To Think About

• Treatment for carbon monoxide poisoning should be started as soon as possible and not be delayed while testing is done.
• Hyperbaric oxygen therapy requires special equipment and may not always be available in your area. But in severe cases of carbon monoxide poisoning, it may reduce your risk of having long-term complications. Your local emergency department will know whether hyperbaric oxygen therapy is available in your area.

Other Places To Get Help

Online Resources

Organizations

Related Information

• Colic
• Headaches
• Health and Safety, Ages 2 to 5 Years
• Health and Safety, Birth to 2 Years
• Influenza
• Radon
• Stroke

References

Citations

1. Mott JA, et al. (2002). National vehicle emissions policies and practices and declining U.S. carbon monoxide-related mortality. JAMA, 288(8): 988-995.

2. Olsen KR (2007). Carbon monoxide section of Poisoning. In SJ McPhee et al., eds., Current Medical Diagnosis and Treatment, 46th ed., pp. 1653. New York: McGraw-Hill.

3. Van Meter KW (2004). Carbon monoxide poisoning. In JE Tintinalli et al., eds., Emergency Medicine: A Comprehensive Study Guide, 6th ed., pp. 1238-1242. New York: McGraw-Hill.

4. Henry CR, et al. (2006). Myocardial injury and long-term mortality following moderate to severe carbon monoxide poisoning. JAMA, 295(4): 398-402.

5. Weaver LK, et al. (2002). Hyperbaric oxygen for acute carbon monoxide poisoning. New England Journal of Medicine, 347(14): 1057-1067.

Other Works Consulted

• Olson KR, Patel MM (2006). Management of poisoning and drug overdose. In DC Dale, DD Federman, eds., ACP Medicine, section 8, chap. 1. New York: WebMD.

• Phin N (2005). Carbon monoxide poisoning (acute), search date August 2004. Online version of BMJ Clinical Evidence. Also available online: http://www.clinicalevidence.com.

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