Every year, about 300 people die in North America after being overcome by carbon monoxide. It is the leading cause of fatal poisonings in North America.

At high concentrations, carbon monoxide (CO) can kill you within a few minutes. One of the major symptoms — confusion — can leave you unable to understand that your life is in danger.

Carbon monoxide is a colourless, odourless, tasteless and non-irritating gas produced by the incomplete burning of fossil fuels. Fuel-burning appliances — like your furnace — normally produce insignificant amounts of carbon monoxide, unless they are not used or maintained properly.

Leaving a car running in a closed garage will produce enough carbon monoxide to overcome and kill you within a few minutes. If left running long enough, a car can fill your home with fatal concentrations of carbon monoxide.

Why is carbon monoxide so dangerous?

You need oxygen to live. Carbon monoxide prevents your bloodstream from absorbing the oxygen you breathe in. It also poisons your red blood cells, preventing them from carrying oxygen.

Without a constant supply of oxygen, your body's tissues and organs will stop functioning. Your brain is particularly at risk. If it's deprived of oxygen for even a short time, it will be damaged. Most of the early symptoms of carbon monoxide poisoning are produced by a brain that's not working right because it has been deprived of oxygen.

What are the symptoms of carbon monoxide poisoning?

The initial symptoms are similar to the flu. They include headache, fatigue, shortness of breath, nausea and dizziness.

If you're exposed to low concentrations of the gas, you might experience shortness of breath when you exert yourself moderately. You will also likely have a slight headache and feel dizzy and nauseous.

At higher concentrations, your headache may become severe. You could have trouble with your vision and your hearing. You will feel dizzy and may collapse or faint with any level of exertion — and you will become confused.

At extreme concentrations, you will slip into a coma within a few minutes and die.

What should I do if I experience some of the symptoms?

At the first sign of any of the symptoms of carbon monoxide poisoning, you need to get out of the house and into fresh air. Call for emergency assistance or get someone to take you to a hospital.

Open your windows to help ventilate the house.

If you enter a home and find someone unconscious, move the person outside. The patient should be kept lying down and warm until emergency personnel arrive.

If the patient regains consciousness, he/she should remain resting for at least two hours. The person should not be encouraged to walk.

If the person has stopped breathing but there is a pulse, begin mouth-to-mouth respiration and continue until the patient begins breathing or help arrives.

How long will it take to recover?

It can take a long time to rid the body of carbon monoxide, but you can speed up the process by administering pure oxygen to the patient. Symptoms won't clear up as soon you get the patient into fresh air. The patient will likely experience headaches, dizziness and confusion for several hours after exposure to carbon monoxide. Very severe cases can lead to pneumonia or permanent brain damage. Some people have died of carbon monoxide poisoning even after it seemed that they had recovered.

What can I do to prevent carbon monoxide poisoning?

• Get a carbon monoxide detector and test the battery regularly, if it runs on batteries. It's the law in many municipalities. Never ignore your CO detector if it goes off. Call 911 and get out of the house.
• Get a professional to inspect all fuel-burning heating systems in your home, including furnaces, boilers, fireplaces, and water heaters, once a year. Your furnace and fireplace should be cleaned annually.
• Furnaces and fireplaces must be properly vented in order to burn fuel properly. Have a professional inspect your chimneys, flues and vents for leakage or blockage. This should be done every year.
• All vents to furnaces, water heaters, boilers and fuel-burning appliances should be checked to make sure they are not loose or disconnected.
• Don't try fixing your furnace or fuel-burning appliances unless you've been trained in how to do it.
• If you have a gas stove or a gas clothes dryer, they should also be inspected for leaks and proper ventilation.
• If your natural gas-fired furnace was built before 1987, consider replacing it. Models built after then include "flame roll-out protection technology," which prevents flames from spilling out of the combustion chamber.
• Never burn charcoal or run your gas barbecue indoors or in an enclosed area.
• Never leave a car idling in a garage. The exhaust, which contains CO, can penetrate the walls.