Carbon Monoxide

Carbon Monoxide (CO) is an odorless, colorless gas that is a by-product of the incomplete burning of fuels (1). Carbon monoxide is produced from cigarette smoke, from human and animal respiration, and when fossil fuels are burned (2). Industrial processes also contribute to CO pollution levels, but the principal source of CO pollution in most large urban areas is the automobile. It adversely affects human health at only a few parts per million and causes death at 250 parts per million (250 ppm)(2). The Centers for Disease Control estimates that each year, 1,500 Americans die from carbon monoxide (CO) poisoning. About 900 of these deaths occur in homes and are preventable (3).

Carbon Monoxide is inhaled and enters the blood stream where it binds chemically to hemoglobin. Hemoglobin carries oxygen to the cells, but when CO binds to it, hemoglobin is unable to bind with oxygen, thereby reducing the amount of oxygen delivered to all tissues of the body. The percentage of hemoglobin inactivated by CO depends on the amount of air breathed, the concentration of CO in air, and length of exposure(1). The initial symptoms of CO poisoning are similar to the flu. They include fatigue, dizziness, irregular breathing, cherry red lips, nausea, headache, paleness, and coughing.

There are many sources of CO around the home. These sources include poorly installed and maintained heating systems, charcoal grills and hibachi pots that are used indoors, gas kitchen stoves that are used for heating, water heaters, and automobile exhaust (3). Carbon monoxide can be easily reduced from all of these sources and CO poisoning is easily preventable. Here are some precautions that can be taken (3):

The following are some very informative external links that pertain to Carbon Monoxide:

EXTOXNET FAQS IndoorAir Pollution Home


1. Measuring Air Quality: The Pollutant Standards Index; Office of Air Quality Planning and Standards, US EPA; EPA 451/K-94-001; February 1994. URL:

2. Greiner, T. Indoor Air Quality: Carbon Monoxide and Carbon Dioxide, ISU Extension Pub # AEN-125, Iowa State University. December 1991. URL:

3. Linn, R. Carbon Monoxide and You. MT 8315, Montana State University Extension. February 1983. URL:

This Page prepared by B.T. Johnson, November 1997 UCD EXTOXNET FAQ Team.