Carbon monoxide - the invisible enemy

Ideally, natural gas burns in an appliance completely and efficiently, mixing with the oxygen in the air to produce harmless carbon dioxide (CO2) and water vapor. But if conditions aren't right, the natural gas won't combust completely, giving off deadly fumes of carbon monoxide (CO).

When humans breathe in carbon monoxide, it enters the bloodstream and depletes oxygen from the blood cells. Exposure is harmful at high levels over a short period of time, or at lower levels over a longer period - overnight, for example. Carbon monoxide can be especially dangerous during the winter, when our homes are sealed up tight.

Symptoms mimic the flu

The early effects of CO poisoning mimic the flu, so watch for these warning signs:

• Headache
• Nausea or vomiting
• Dizziness and disorientation
• Muscle weakness or fatigue

If the flu-like symptoms are NOT accompanied by fever, if everyone in the family is ill, or if the symptoms disappear when you leave the house, you may have a CO problem - have your gas appliances checked by a service technician right away.

It's important to catch CO problems in the early stages. If exposure continues, the poisoning reaches the central nervous system, resulting in memory loss, slurred speech, loss of consciousness and eventually death.

Carbon monoxide poisonings are often detected by family or friends telephoning a disoriented victim; if you notice any of these symptoms in someone you know, call 911.

Preventing carbon monoxide

Prevention is the only way to deal with carbon monoxide, and the best prevention is regular inspection by a service technician.

An appliance could produce carbon monoxide if:

• Boxes, laundry or other materials are blocking the base, restricting oxygen flow.
• The vent hood, pipes or flues are blocked or corroded.
• The unit is installed or adjusted improperly.
• It's used incorrectly (i.e., heating a room with a gas stove).
• The heat exchanger is cracked.

Natural gas furnaces should be inspected every year; other appliances, such as water heaters, clothes dryers and stoves, should be checked every two years. If you have a natural gas fireplace, it should be serviced regularly as well.

Carbon monoxide concentrations and symptoms

• 35 parts per million (ppm) = No adverse effects within eight hours
• 200 ppm = Mild headache after two to three hours of exposure
• 400 ppm = Headache and nausea after one to two hours
• 800 ppm = Headache, nausea and dizziness after 45 minutes; collapse after two hours
• 1000 ppm = Loss of consciousness after one hour
• 1600 ppm = Headache, nausea and dizziness after 20 minutes; unconsciousness after 30 minutes
• 3200 ppm = Headache, nausea and dizziness after 5-10 minutes; unconsciousness after 30 minutes
• 12,800+ ppm = Immediate physiological effects; unconsciousness and danger of death after only one to three minutes

Learn more:

• Carbon Monoxide Questions & Answers - By the U.S. Consumer Products Safety Commission
• Carbon Monoxide Poisoning - By the Mayo Clinic
• Preventing Carbon Monoxide Fact Sheet [pdf] - By the American Lung Association