An Introduction to Carbon Monoxide (CO)

A device many people have in their homes                                           
to give them a sense of security may still
miss low-level carbon monoxide leaks that
can cause illnesses and kill pets,
a Channel 4 I-Team investigation finds.  Click for more.
Carbon monoxide is an odorless, colorless and toxic gas. Because it is impossible to see, taste or smell the toxic fumes, CO can kill you before you are aware it is in your home. At lower levels of exposure, CO causes mild effects that are often mistaken for the flu. These symptoms include headaches, dizziness, disorientation, nausea and fatigue. The effects of CO exposure can vary greatly from person to person depending on age, overall health and the concentration and length of exposure.

ALERT: Put generators outside.

Never use a generator inside homes, garages, crawlspaces, sheds, or similar areas. Deadly levels of carbon monoxide can quickly build up in these areas and can linger for hours, even after the generator has shut off.


Carbon monoxide (CO) is a colorless, practically odorless, and tasteless gas or liquid. It results from incomplete oxidation of carbon in combustion.  Burns with a violet flame.  Slightly soluble in water; soluble in alcohol and benzene.  Specific gravity 0.96716;  boiling point -190oC; solidification point -207oC; specific volume 13.8 cu. ft./lb. (70oF).  Auto ignition temperature (liquid) 1128oF.  Classed as an inorganic compound.
Source:  "The Condensed Chemical Dictionary," 9th ed., revised by Gessner G. Hawley, Van Nostrand Reinhold Co., NY, 1977.

Sources of Carbon Monoxide

Unvented kerosene and gas space heaters; leaking chimneys and furnaces; back-drafting from furnaces, gas water heaters, wood stoves, and fireplaces; gas stoves; generators and other gasoline powered equipment; automobile exhaust from attached garages; and tobacco smoke.  Incomplete oxidation during combustion in gas ranges and unvented gas or kerosene heaters may cause high concentrations of CO in indoor air.  Worn or poorly adjusted and maintained combustion devices (e.g., boilers, furnaces) can be significant sources, or if the flue is improperly sized, blocked, disconnected, or is leaking.  Auto, truck, or bus exhaust from attached garages, nearby roads, or parking areas can also be a source.

Health Effects Associated with Carbon Monoxide

At low concentrations, fatigue in healthy people and chest pain in people with heart disease. At higher concentrations, impaired vision and coordination; headaches; dizziness; confusion; nausea. Can cause flu-like symptoms that clear up after leaving home. Fatal at very high concentrations.  Acute effects are due to the formation of carboxyhemoglobin in the blood, which inhibits oxygen intake.  At moderate concentrations, angina, impaired vision, and reduced brain function may result.  At higher concentrations, CO exposure can be fatal.

Levels in Homes

Average levels in homes without gas stoves vary from 0.5 to 5 parts per million (ppm). Levels near properly adjusted gas stoves are often 5 to 15 ppm and those near poorly adjusted stoves may be 30 ppm or higher.

Steps to Reduce Exposure to Carbon Monoxide

It is most important to be sure combustion equipment is maintained and properly adjusted.  Vehicular use should be carefully managed adjacent to buildings and in vocational programs.  Additional ventilation can be used as a temporary measure when high levels of CO are expected for short periods of time.

  • Keep gas appliances properly adjusted.
  • Consider purchasing a vented space heater when replacing an unvented one.
  • Use proper fuel in kerosene space heaters.
  • Install and use an exhaust fan vented to outdoors over gas stoves.
  • Open flues when fireplaces are in use.
  • Choose properly sized wood stoves that are certified to meet EPA emission standards. Make certain that doors on all wood stoves fit tightly.
  • Have a trained professional inspect, clean, and tune-up central heating system (furnaces, flues, and chimneys) annually. Repair any leaks promptly.
  • Do not idle the car inside garage.

Measurement Methods

Some relatively high-cost infrared radiation adsorption and electrochemical instruments do exist.  Moderately priced real-time measuring devices are also available.  A passive monitor is currently under development.

Standards or Guidelines

No standards for CO have been agreed upon for indoor air.  The U.S. National Ambient Air Quality Standards for outdoor air are 9 ppm (40,000 micrograms per meter cubed) for 8 hours, and 35 ppm for 1 hour.

Additional Resources

To report a dangerous product or a product-related injury, call the Consumer Product Safety Commission's (CPSC) hotline at (800) 638-2772 or CPSC teletypewriter at (800) 638-8270.  Consumer can obtain recall information at CPSC's web site -  Consumers can report product hazards to

Links to Additional Information

EPA's Office of Air and Radiation page - "CO - How Carbon Monoxide Affects the Way We Live and Breathe"

EPA's Office of Research and Development:

Centers for Disease Control and Prevention (CDC)
National Center for Environmental Health

Carbon Monoxide Poisoning Fact Sheet - (offered in many languages) -

U.S. Consumer Product Safety Commission (CPSC)
Office of Information and Public Affairs
Washington, D.C. 20207

CPSC protects the public from the unreasonable risk of injury or death from 15,000 types of consumer products under the agency's jurisdiction. To report a dangerous product or a product-related injury, you can go to CPSC's forms page - and use the first on-line form on that page. Or, you can call CPSC's hotline at (800) 638-2772 or CPSC's teletypewriter at (800) 638-8270, or send the information to

U.S. Department of Homeland Security
U.S. Fire Administration, 16825 S. Seton Ave., Emmitsburg, MD 21727
Voice: (301) 447-1000 Fax: (301) 447-1346 Admissions Fax: (301) 447-1441

American Lung Association

Occupational Safety and Health Administration

U.S. National Library of Medicine and the National Institute of Health

"Carbon Monoxide Poisoning"


About Carbon Monoxide Detectors

CPSC Recommends Carbon Monoxide Alarm for Every Home (January 18, 2001 CPSC Release # 01-069)

The U.S. Consumer Product Safety Commission (CPSC) recommends that every home should have a carbon monoxide (CO) alarm. CPSC also urges consumers to have a professional inspection of all fuel- burning appliances -- including furnaces, stoves, fireplaces, clothes dryers, water heaters, and space heaters -- to detect deadly carbon monoxide leaks.  CPSC recommends that every home should have at least one CO alarm that meets the requirements of the most recent Underwriters Laboratories (UL) 2034 standard or International Approval Services 6-96 standard.

 Product Safety Tips - Carbon Monoxide Alarms -  Underwriters' Laboratory

"Your Home and Your Health"   Canadian Mortgage and Housing Corporation (CMHC)

Disposing of Smoke Detectors - - EPA's Radiation Protection Division

U.S. Coast Guard Boating Safety Carbon Monoxide Warning

Portable Generators

  1. The Centers for Disease Control and Prevention -Safety Alert. 

Portable generators are useful when temporary or remote electric power is needed, but they also can be hazardous. The primary hazards to avoid when using a generator are carbon monoxide (CO) poisoning from the toxic engine exhaust, electric shock or electrocution, and fire. 

  1. Department of Homeland Security, U.S. Fire Administration's Portable Generator Hazards page -
  2. Surviving the Aftermath of Hurricane Katrina CPSC Warns of Deadly Post-Storm Dangers with Portable Generators, Candles and Wet Appliances, U.S. Consumer Product Safety Commission, Office of Information and Public Affairs, Washington, DC, August 31, 2005, Release #05-251
  1. ALERT!! Preventing Carbon Monoxide Poisoning from Small Gasoline-Powered Engines and Tools. (1996)

This joint alert from NIOSH, CDPHE, CPSC, OSHA and EPA warns that people using gasoline-powered tools such as high-pressure washers, concrete cutting saws (walk-behind/hand-held), power trowels, floor buffers, welders, pumps, compressors, and generators in buildings or semi-enclosed spaces have been poisoned by Carbon Monoxide. Recommendations for preventing CO poisoning are provided for employers, equipment users, tool rental agencies, and tool manufacturers.

Single copies of the Alert [DHHS (NIOSH) Publication No. 96-118] are available for free from:  Publication Dissemination, IED, National Institute for Occupational Safety and Health; 4676 Columbia Parkway, Cincinnati, OH 45226
fax number: (513) 533-8573, phone number: 1-800-35-NIOSH (1-800-356-4674)


Protect Your Family and Yourself from Carbon Monoxide Poisoning

Discusses health hazards associated with exposure to carbon monoxide (CO), a colorless, odorless gas which can cause headaches, dizziness, nausea, faintness, and, at high levels, death. Provides guidance on what to do if you think you are suffering from CO poisoning and what to do to prevent exposure to CO. Also included is a brief discussion about carbon monoxide detectors.

  • PDF Version (PDF, 2 pp, 65KB)
  • EPA-402-F-96-005, October 1996

Proteja su vida y la de su familia: Evite el envenenamiento con monóxido de carbono

The Carbon Monoxide fact sheet has also been translated into:

  • Vietnamese [EPA 402-F-99-004C]
  • Chinese [EPA 402-F-99-004A], and
  • Korean [EPA 402-F-99-004B]

Publications/Documents from the Consumer Product Safety Commission (CPSC)

Link to CPSC Indoor Air Quality Publications -

The "Invisible" Killer (CPSC Document #464)

Prepared by the U.S. Consumer Product Safety Commission, this leaflet describes symptoms of carbon monoxide poisoning, sources of carbon monoxide in the home, and actions that can reduce the risk of carbon monoxide poisoning. 

Carbon Monoxide Fact Sheet (CPSC Document #466)

Discusses carbon monoxide (CO) hazards; and prevention and detection of dangerous CO levels.

What You Should Know About Combustion Appliances and Indoor Air Pollution (CPSC Document #452)

This booklet answers some common questions you may have about the potential for one specific type of hazard - indoor air pollution - associated with one class of appliances - combustion appliances. 

Responding to Residential Carbon Monoxide Incidents , July 23, 2002 (CPSC Publication)

Guidelines for first responders to residential carbon monoxide incidents.

Carbon Monoxide Poisoning From Camping Equipment (CPSC Document #5008)

Safety Alert: Discusses carbon monoxide (CO) poisoning and explains how C0 can cause CO poisoning from camping equipment such as portable camping heaters, lanterns, stoves inside tents, campers and vehicles. Provides steps to take to prevent such poisonings and how to recognize the symptoms of CO poisoning.

Carbon Monoxide Detectors Can Save Lives (CPSC Document #5010)

Safety Alert: Discusses how (CO) detectors can save your life describes the symptoms of CO poisoning. 

Deaths From Burning Charcoal in Homes, Vehicles, and Tents (CPSC Document #5012)

Safety Alert: Discusses the hazards of carbon monoxide, which causes 25 deaths from carbon monoxide each year in these environments. 

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