The colorless, odorless, tasteless gas builds up without warning and can kill in minutes. Hundreds of people die accidentally each year from carbon monoxide poisoning caused by malfunctioning or improperly used fuel-burning appliances. Automobiles, gas furnaces, gas water heaters, wood fires and gas stoves are all producers of carbon monoxide. Iowa State University Extension offers the following indications that may signal a carbon monoxide problem in your home:

• Excess moisture in the house.
• An occupant may feel nauseous, drowsy, groggy, or sick when in the house, but once out of the house, symptoms go away.
• Chimneys on the outside of the house get cold, and don't pull gases out as well.
• A poorly maintained chimney with no cap.

Prevention is the key to avoiding carbon monoxide poisoning. The U.S. Environmental Protection Agency offers "dos and don'ts" to prevent carbon monoxide-related accidents:

• Do have fuel-burning appliances inspected by trained professionals at the beginning of every heating season.
• Do choose appliances that vent their fumes to the outside.
• Do read and follow all of the instructions that accompany any fuel-burning device.
• Don't idle the car in a garage - even if the door to the outside is open. Fumes can build up very quickly in the garage and living area of your home.
• Don't ever use a charcoal grill indoors.
• Don't sleep in any room with an un-vented gas or kerosene space heater.
• Don't use any gasoline-powered engines (mowers, weed trimmers, snow blowers, chain saws, small engines or generators) in enclosed spaces.