Carbon monoxide (CO) is an odorless,
colorless gas formed when carbon in fuels does not burn completely. Hundreds
of Americans die every year from carbon monoxide poisoning caused by improperly
used or malfunctioning fuel-burning appliances. Fetuses, young children,
and the elderly are particularly susceptible to carbon monoxide poisoning.
Carbon monoxide is a “combustion pollutant” — a gas
(or particle) that comes from burning carbon-based materials. Combustion
pollutants are most often released into the home by vented or unvented
appliances and vehicles running in an attached garage. Carbon monoxide
isproduced when there is a lack of oxygen or enough heat to burn fuels
completely. The smoldering burn of incense or cigarettes also produces
When carbon monoxide enters the bloodstream, it reduces
the amount of oxygen received by the body’s organs and tissues.
Unborn babies, children, the elderly, and people with respiratory problems
or heart disease are especially sensitive to carbon monoxide. Even at
low levels, carbon monoxide causes serious health problems, and the longer
the exposure, the more damage that occurs.
Low levels of carbon monoxide can cause flu-like
symptoms, headaches, dizziness, and make it difficult to think clearly.
Often a family may not realize that their illnesses are related to chronic
exposure to carbon monoxide in the home.
At higher levels of exposure, carbon monoxide is related to visual impairment,
reduced work capacity, poor learning ability, and difficulty in performing
complex tasks. At very high levels, carbon monoxide can also kill. Each
year, more than 200 Americans accidentally die from carbon monoxide poisoning
in the home, unrelated to fires and engine exhaust (other sources of carbon
monoxide poisoning). Seventy-six percent of these deaths are from carbon
monoxide released from heating systems. Another eight percent are from
gas water heaters. Many victims of carbon monoxide poisoning die in their
sleep. An additional 10,200 people visit the emergency room due to accidental
carbon monoxide poisoning from consumer products.
Common indoor sources of carbon monoxide are:
- Cars in attached garages, especially when the
engine is being warmed up
- Combustion appliances, such as:
- Gas stoves (with a flame that burns yellow)
- House fires
- Non-electric space heaters used indoors without enough fresh
- Furnaces with cracked heat exchangers or leaking chimneys
that leak gases into the ventilation system
The main indoor cause of carbon monoxide poisoning are combustion appliances
(those which burn fuels for warmth, cooking, or decorative purposes),
such as furnaces, space heaters, gas ranges, gas water heaters, and fireplaces.
The most serious effects of carbon monoxide in the home occur in the winter,
when homes are closed up more tightly. If combustion appliances are used
properly and are well maintained, the amount of carbon monoxide produced
is not usually hazardous to human health. However, if appliances are used
incorrectly or vented improperly, the levels of carbon monoxide indoors
can become dangerous.
Vented appliances are designed to be used with a pipe, chimney, duct,
or other device that sends the pollutants outside the home. If a vent
is blocked, leaking, or improperly installed, the appliance can release
a large amount of combustion pollutants, including carbon monoxide, directly
into the home. Unvented appliances do not have a pipe, chimney, or other
duct to carry the pollutants outside the home, and therefore disperse
carbon monoxide and other pollutants throughout the home.
Common outdoor sources are:
- Vehicle exhaust
- Industrial processes
- Fuel combustion in incinerators and boilers
Since carbon monoxide is impossible to see or smell,
carbon monoxide detectors and alarms can be another key part of protecting
against carbon monoxide poisoning.
The Consumer Product Safety Commission recommends
placing carbon monoxide detectors on each level of the home and near all
sleeping areas. Although the presence of a carbon monoxide detector can
help identify problems, they should not be used in place of preventive
efforts, nor should their silence be interpreted as unquestionable proof
of the absence of carbon monoxide hazards.
The U.S. Environmental Protection Agency (EPA) states
that the technology of carbon monoxide detectors is still in development
and that they are not generally considered as reliable when compared to
current smoke detectors. In fact, in some laboratory tests, very high
levels of carbon monoxide were not detected by properly installed units.
Concerns have also been raised that these alarms do not sound until the
level of carbon monoxide reaches very high levels.
Despite these potential reservations, these detectors
can be useful tools in assessing hazards in the home, but they should
not replace preventative measures against carbon monoxide poisoning.
The Alliance has informative
materials and tools for low-cost carbon monoxide testing,
produced as part of its past Community Environmental Health Resource Center
Tenants, landlords, and homeowners can reduce the likelihood of hazardous
carbon monoxide exposures by taking steps such as these:
- Choose and use heating appliances wisely. Properly
install, maintain, ventilate and check regularly all fuel-fired heating
systems, water heaters, appliances, fireplaces, wood and coal stoves,
and space heaters.
- Always ensure proper ventilation
in any room where a fuel-burning appliance of any sort is in use.
- Do not use any gas appliances (i.e. range, stove)
for home heating purposes.
- Do not burn any type of fuel in the home except
firewood in an appropriately maintained and ventilated fireplace.
- Leave garage doors open while the car is running
and limit the amount of time a running car is in the garage. (It is
also important to note that carbon monoxide can build up inside the
car itself while operating if there are leaks in the exhaust system.)
Even with precautionary measures, a situation involving high levels of
carbon monoxide in the home may occur. Whether discovered by an individual
experiencing symptoms or an active alarm, there are certain procedures
to take if high levels of carbon monoxide are present.
- Immediately remove anyone who is experiencing
symptoms from the environment and seek medical attention.
- Open windows and doors to ventilate the space,
turn off any potential source of the carbon monoxide, and notify the
landlord and/or fuel supplier.
- Arrange for the proper inspection of all fuel-fired
systems, appliances, and fireplaces and further arrange for any necessary
Alliance for Healthy Homes
American Lung Association (site
in English) (sitio
American National Standards Institute (ANSI), American Society of Heating,
Refrigeration, and Air-Conditioning Engineers (ASHRAE), Ventilation for
Acceptable Indoor Air Quality, Standard 62-2001, ISSN 1041-2336
Canada Department of National Health and Welfare - Exposure Guidelines
for Residential Indoor Air Quality, Ottawa. April 1987
Carbon Monoxide Headquarters
- Operated by Dr. David Penney, Professor of Occupational and Environmental
Health in the School of Medicine at Wayne State University, this site
contains links to background information, research articles, data, and
other resources focused solely on carbon monoxide.
Thom, Ischiropoulos, and Xu, University of Pennsylvania Medical Center
Mechanism To Explain Carbon Monoxide Poisoning Identified,
September 27, 1997.
US Centers for Disease Control and Prevention,
Carbon Monoxide Poisoning Program
- This area provides a collection of documents and resources on carbon
monoxide, including a fact sheet on the gas (English)
US Consumer Product Safety Commission
US Environmental Protection Agency
- General IAQ Hotline (IAQINFO): 1-800-438-4318
Sponsored by EPA, this hotline provides general information on indoor
air quality and related pollutants.
- Su Familia (Your Family): 1-866-SU FAMILIA
Alliance for Hispanic Health sponsors this helpline to
offer Hispanic consumers free, reliable and confidential health information
in Spanish and English and help navigate callers through the health