Carbon monoxide is colorless & odorless. At high concentrations, it is lethal (that is, deadly) within minutes. Carbon monoxide is produced when any fuel is burned. When combustion appliances are properly maintain, then carbon monoxide is usually not a problem. But dangerous levels of carbon monoxide can result if the appliances are not working or if they are used incorrectly.
Symptoms of carbon monoxide poisoning depend on the level of exposure. Low levels can cause nausea, headaches and shortness of breath. These are similar to flu symptoms, and therefore may not alert you to a carbon monoxide problem. Moderate levels cause severe headaches, dizziness, confusion, nausea, or fainting. If even moderate levels continue, death could result.
If you suspect you are experiencing symptoms from carbon monoxide poisoning, then get fresh air immediately. Open the doors and windows, shut down the possible carbon monoxide source, and go outside. Go to the emergency room and tell them you suspect carbon monoxide poisoning. For a short time after exposure, it can be confirmed with a blood test.
Given the danger of carbon monoxide, the greatest course of action to take is prevention. Have all of your fuel burning appliances inspected at the beginning of heating season. This includes oil and gas furnaces, gas water heaters, gas stoves and ovens, gas dryers, gas or kerosene space heaters, fireplaces and wood stoves.
Only use fuel burning appliances that vent fumes to the outside. If you must use an unvented appliance indoors, keep doors to the rest of the house open, and raise a window slightly to make sure there is enough outside air for ventilation.
Don't leave the car idling in the garage. Never heat your home with a gas oven. Never use a charcoal grill inside. Don't attend sleep in a room with an unvented gas or kerosene heater.
Consider purchasing a carbon monoxide detector. But remember that carbon monoxide is colorless and odorless, so you may not know if a possible alarm is false or a real emergency. Owning a detector should never serve as a replacement for proper inspection and maintenance of your fuel burning appliances.