Carbon Monoxide Risks at Home

In the past decade, people have become more aware of the risk of carbon monoxide (or CO) poisoning in the home. The nonprofit National Fire Protection Association (NFPA) prepared this fact sheet to help people protect themselves and their families against CO poisoning.

What is carbon monoxide?

Carbon monoxide (CO) is an invisible, odorless, colorless gas created when fossil fuels (such as gasoline, wood, coal, propane, oil, and methane) burn incompletely. In the home, heating and cooking equipment are possible sources of CO. Vehicles or generators running in an attached garage could also produce dangerous levels of CO.

However, consumers can protect themselves against CO poisoning by installing CO alarms inside their homes; by properly installing, using, venting, and maintaining heating and cooking equipment; and by being cautious with vehicles or generators in attached garages.

What is the effect of exposure to CO?

CO is poisonous and can kill cells of the body. CO also replaces oxygen in the bloodstream, leading to suffocation. Mild effects feel like the flu, while severe effects include difficulty breathing and even death.

Just how sick people get from CO exposure varies greatly from person to person, depending on age, overall health, concentration of exposure (measured in parts per million), and length of exposure. Higher concentrations are dangerous even for a short time.

When blood carries CO rather than oxygen, the CO-carrying cells are called carboxyhemoglobin (COHb), in contrast to normal oxygen-carrying hemoglobin. The percentage of the blood that is carboxyhemoglobin -- also called carboxyhemoglobin saturation -- measure show badly a person is affected by CO. A doctor can measure COHb in the blood but cannot measure CO in the body directly. The more CO in the body, the higher the COHb, and the sicker the person will be.

What is your risk of CO poisoning?

Deaths from unintentional poisoning by gas or vapors, chiefly CO -- about 600 in 1996, according to the National Safety Council -- are fairly rare, and the number has been declining somewhat steadily, down more than half since the early 1980s. Of all the unintentional gas and vapor poisoning deaths in the U.S., more than one-third involve motor vehicle exhaust gas, and more than one fourth involve heating or cooking equipment. The total reflects more than CO-related deaths; it also reflects deaths resulting from other gases, such as natural gas leaks from pipelines.*

Deaths from unintentional CO poisoning have dropped sharply in recent years, thanks to lower CO emissions from automobiles and safer heating and cooking appliances. Deaths from "smoke inhalation" (largely CO) in fires and suicides involving CO are far more common causes of gas-related suffocation deaths.

According to the U.S. Consumer Product Safety Commission, 164 CO-related non-fire deaths were attributed to heating and cooking equipment in 1994.** The specific types of equipment were:

* Gas-fueled space heaters (70 deaths)
* Gas-fueled furnaces (48 deaths)
* Charcoal grills (15 deaths)
* Gas-fueled ranges (9 deaths)
* Liquid-fueled heaters (9 deaths)
* Gas-fueled water heaters (7 deaths)
* Solid-fueled heaters (6 deaths)

As with fire deaths, the risk of unintentional CO death is highest for the very young (ages 4 or under) and the very old (ages 75 or above).

*National Safety Council's Accident Facts, 1981-97.

** The latest year for which statistics are available at this level of detail.

How can you protect yourself from CO poisoning?

Install CO alarms inside your home to provide early warning of accumulating CO. However, a CO alarm is no substitute for safe practices. The best defenses against CO poisoning are safe use of vehicles (particularly in attached garages) and proper installation, use, venting and maintenance of household cooking and heating equipment.