Carbon monoxide is a colorless, odorless and tasteless gas. But the danger it poses is real. Carbon monoxide replaces oxygen in your blood — and the consequences can be fatal. In the U.S., more people die each year of exposure to carbon monoxide than of any other type of poison.

Carbon monoxide is produced by appliances and other devices that burn gas, petroleum products, wood and other fuels. Sometimes carbon monoxide can accumulate to dangerous levels in your car, home or other poorly ventilated areas.

The signs of carbon monoxide poisoning can be subtle — but, simple precautions can save your life.

Symptoms of carbon monoxide poisoning may include:

• Dull headache, the most common early symptom
• Dizziness
• Nausea
• Vomiting
• Chest pain
• Confusion
• Irritability
• Impaired judgment
• Loss of consciousness

Carbon monoxide poisoning can be especially dangerous for people who are sleeping or intoxicated. The fumes may be fatal before they realize there's a problem.

Carbon monoxide poisoning is caused by inhaling carbon monoxide fumes. When there's too much carbon monoxide in the air, your body replaces the oxygen in the hemoglobin of your red blood cells with carbon monoxide. This keeps life-sustaining oxygen from reaching your tissues and organs.

Various appliances fueled by wood or gas produce carbon monoxide, including:

• Fuel-burning space heaters
• Furnaces
• Charcoal grills
• Cooking ranges
• Water heaters
• Fireplaces
• Portable generators, including those often used on houseboats
• Wood-burning stoves
• Car and truck engines

Normally the amount of carbon monoxide produced by these sources isn't cause for concern. But if appliances aren't kept in good working order or if they're used in a closed or partially closed space — such as using a charcoal grill indoors or running your car in a closed garage — the carbon monoxide can build to dangerous levels. Even swimming behind a motorboat or riding in the back of an enclosed pickup truck can be dangerous.

Smoke inhalation during a fire also can cause carbon monoxide poisoning.

Carbon monoxide fumes are dangerous for anyone. Some people are more susceptible to the effects of carbon monoxide, including:

• Unborn babies
• Infants
• Older adults
• People who smoke
• People who have chronic heart disease, anemia or respiratory problems

If you suspect you've been exposed to carbon monoxide, get into fresh air immediately and seek emergency medical care. If possible, open windows and doors on the way out of the house.

Your doctor will ask about your medical history. If the doctor suspects carbon monoxide poisoning, he or she will take a blood sample to measure the amount of carbon monoxide in your blood.

Carbon monoxide poisoning is dangerous. Depending on the degree and length of exposure, carbon monoxide poisoning can cause:

• Permanent brain damage
• Damage to your heart, possibly leading to life-threatening cardiac complications years after the poisoning
• Death

The goal of treatment is to replace the carbon monoxide in your blood with oxygen. In the hospital, you may breathe pure oxygen through a mask placed over your nose and mouth. This helps oxygen reach your organs and tissues. If you can't breathe on your own, a machine (ventilator) may do the breathing for you.

In some cases, hyperbaric oxygen therapy is recommended. With this therapy, you're placed in a full-body pressurized chamber. Inside the chamber, air pressure is more than twice as high as normal atmospheric pressure. This speeds the removal of carbon monoxide from your blood.

Simple precautions can help prevent carbon monoxide poisoning. Consider these do's and don'ts:

• Invest in carbon monoxide detectors. Install a carbon monoxide detector on every floor or level of your home. Install additional detectors outside individual bedrooms. Check the batteries every time you check your smoke detector batteries — at least twice a year. If the alarm sounds, leave the house and call the fire department or local utility company from a nearby phone.
• Open the garage door before starting your car. Never run your car in a closed garage. If you have an attached garage, keep the garage door open and the door to the house firmly closed while the car is running. Remove snow or other debris from the tailpipe before using the car.
• Use gas appliances as recommended. Never use a gas stove or oven to heat your home. Use portable gas camp stoves only outdoors. Use fuel-burning space heaters only when someone is awake to monitor them and doors or windows are open to provide fresh air. Don't run a generator in an enclosed space, such as the basement or garage.
• Keep your gas appliances and fireplace in good repair. Make sure your appliances are properly vented. Clean your fireplace chimney and flue every year. Ask your utility company about yearly checkups for any gas appliances.

Take action quickly
If you notice signs or symptoms of carbon monoxide poisoning — headache, dizziness, nausea, vomiting, chest pain, confusion — get into fresh air and seek emergency medical care.

Fix the problem
If you were poisoned in your home, it's important to find and repair the source of the carbon monoxide before you return. Your local fire department or utility company can help.