You cannot see or smell carbon monoxide (CO), but at high levels it can kill a person in minutes. It is the leading cause of poisoning death, with over 500 victims in the United States each year.
Carbon monoxide is produced whenever a fuel such as gas, oil, kerosene, wood or charcoal is burned. The amount of CO produced depends mainly on the quality or efficiency of combustion. A properly functioning burner, whether natural gas or liquefied petroleum gas (LPG), has efficient combustion and produces little CO. An out-of-adjustment burner can produce life-threatening amounts of CO without any visible warning signs.
When appliances that burn fuel are maintained and used properly, the amount of CO produced usually is not hazardous. But if appliances are not working properly or are used incorrectly, dangerous levels of CO can collect in an enclosed space. Hundreds of Americans die accidentally every year from CO poisoning caused by malfunctioning or improperly used fuel-burning appliances.
Common sources of CO
Accumulation of combustion gases can occur when a blocked chimney, rusted heat exchanger or broken chimney connector pipe (flue) prevents combustion gases from being exhausted from the home. CO also can enter the home from an idling car or from a lawnmower or generator engine operating in the garage.
Another source for CO is backdrafting. When ventilation equipment, such as a range-top vent fan, is used in a tightly sealed home, reverse air flow can occur in chimneys and flues. An operating fireplace also can interact with the flue dynamics of other heating appliances. Again, backdrafting may result.
Other common sources of CO include unvented, fuel-burning space heaters (especially if malfunctioning) and indoor use of a charcoal barbeque grill. CO is produced by gas stoves and ranges and can become a problem with prolonged, improper operation — for example, if these appliances are used to heat the home. Flame color does not necessarily indicate CO production. However, a change in the gas flame’s color can indicate a CO problem. If a blue flame becomes yellow, CO often is increased.
While larger combustion appliances are designed to be connected to a flue or chimney to exhaust combustion byproducts, some smaller appliances are designed to be operated indoors without a flue. Appliances designed as supplemental or decorative heaters (including most unvented gas fireplaces) are not designed for continuous use. To avoid excessive exposure to pollutants, never use these appliances for more than four hours at a time.
When operating unvented combustion appliances, such as portable space heaters and stoves, follow safe practices. Besides observing fire safety rules, make sure the burner is properly adjusted and there is good ventilation. Never use these items in a closed room. Keep doors open throughout the house, and open a window for fresh air. Never use outdoor appliances such as barbeque grills or construction heaters indoors. Do not use appliances such as ovens and clothes dryers to heat the house.
Inspect heating equipment. To reduce the chances of backdrafting in furnaces, fireplaces and similar equipment, make sure flues and chimneys are not blocked. Inspect metal flues for rust. In furnaces, check the heat exchanger for rust and cracks. Soot also is a sign of combustion leakage. When using exhaust fans, open a nearby window or door to provide replacement air
CO poisoning symptoms
The initial symptoms of CO poisoning are similar to the flu but without the fever. They include headache, fatigue, shortness of breath, nausea, dizziness, vomiting, disorientation, and loss of consciousness.
In more technical terms, CO bonds tightly to the hemoglobin in red blood cells, preventing them from carrying oxygen throughout the body. If you have any of these symptoms and if you feel better when you go outside your home and the symptoms reappear when you go back inside, you may have CO poisoning.
If you experience symptoms that you think could be from CO poisoning, get fresh air immediately. Open doors and windows, turn off combustion appliances, and leave the house. Go to an emergency room and tell the physician you suspect CO poisoning.
If CO poisoning has occurred, it often can be diagnosed by a blood test done soon after exposure. Be prepared to answer the following questions for the doctor:
• Do your symptoms occur only in the house?
• Is anyone else in your household complaining of similar symptoms?
• Did everyone’s symptoms appear about the same time?
• Are you using any fuel-burning appliances in the home?
• Has anyone inspected your appliances lately?
• Are you certain these appliances are properly working?
Because CO is a colorless, tasteless, and odorless gas that is quickly absorbed by the body and the symptoms often resemble other illnesses, it is often known as the “silent killer.”
Prevention is the key
At the beginning of every heating season, have a trained professional check all your fuel-burning appliances: oil and gas furnaces, gas water heaters, gas ranges and ovens, gas dryers, gas or kerosene space heaters, fireplaces and wood stoves. Make certain that the flues and chimneys are connected, in good condition and not blocked.
Whenever possible, choose appliances that vent fumes to the outside. Have them properly installed, and maintain them according to manufacturers’ instructions. Read and follow all instructions that accompany any fuel-burning device. If you cannot avoid using an unvented gas or kerosene space heater, carefully follow the cautions that come with the device. Use the proper fuel and keep doors to the rest of the house open. Crack a window to ensure enough air for ventilation and proper fuel burning.
Proper installation, operation and maintenance of combustion appliances in the home are most important in reducing the risk of CO poisoning.
In recent years, CO alarms have become widely available. When selecting a CO alarm, make sure it meets the stringent requirements of Underwriters Laboratories (UL) or International Approval Service (IAS). Modern CO alarms can provide warnings for even nonlethal levels of this dangerous pollutant. However, do not think of the alarm as the “be all, end all” to alert you to dangerous CO levels. The U.S. Consumer Product Safety Commission recommends having at least one CO alarm in every home, placed outside of the sleeping area. Homes with several sleeping areas require multiple alarms.
Look for an alarm with a long-term warranty and one that easily can be self-tested and reset to ensure proper functioning.
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