What is carbon monoxide?
Carbon monoxide (CO) is a gas that is produced when fuel—gasoline, propane, natural gas, oil, wood, or coal—is burned. CO is extremely dangerous to people when emitted in an enclosed, unventilated area, such as a house, garage or car.

Why is it harmful?
When CO is breathed, it is absorbed into the bloodstream and displaces oxygen necessary to vital organs. It can eventually cause permanent brain damage and death.

CO is especially dangerous because it cannot be seen or smelled. People may feel ill or become unconscious without realizing they are being poisoned and need to get to fresh air immediately.

How would someone be exposed to CO?
Winter is when most CO poisoning incidents happen, because people use heaters, leave cars idling to warm up, and because snow drifts can block vents and tailpipes. Poisoning can happen when:

• A furnace, gas stove or water heater is faulty or installed improperly.

• The outside vent to a fuel-burning appliance becomes covered with snow.

• A fireplace chimney or stove pipe becomes clogged or blocked.

• A charcoal grill is used indoors.

• A car or gas-powered snow- or leaf-blower is left running in a closed garage.

• A car is running while parked with snow blocking the tailpipe.

With electric heaters and appliances, you do not need to worry about CO.

What happens during poisoning?
Both children and adults can become very ill and even die within minutes or hours of exposure, depending on the level. Pregnant women, their unborn children, babies, heavy smokers, and people with anemia, heart or lung disease may be affected more quickly or seriously. Symptoms and effects vary between individuals, even at the same level of CO exposure, but people typically experience flu-like symptoms, including: dizziness, fatigue, weakness, headache or vomiting, trouble breathing, confusion, ringing in the ears, heart fluttering, gastrointestinal complaints, increased blood pressure, or bright red or pink skin, mucous membranes or nails.

However, death from CO poisoning can result even if none of these symptoms occur first. In some cases, people fall unconscious before ever feeling ill.

Some CO poisoning survivors have described drifting in and out of consciousness, but being completely immobilized and unable to get themselves out of the area.