The dangers of carbon monoxide

Carbon monoxide is a dangerous gas that you cannot smell or see. It is produced as a common byproduct of the combustion (burning) of fossil fuels. Most fuel-burning equipment (natural gas, gasoline, propane, fuel oil and wood), if properly installed and maintained, produces little carbon monoxide. The byproducts of combustion are usually safely vented to the outside.

If there is a shortage of oxygen to the burner of an appliance or piece of equipment, however, or venting is inadequate, carbon monoxide can increase to dangerous levels. Common sources of carbon monoxide include gasoline engines running in closed garages, fuel-burning space heaters or water heaters with improper venting and blocked chimneys or vent pipes.

If you breathe in carbon monoxide, it enters your bloodstream and robs oxygen from blood cells. This is called carbon monoxide poisoning.

Prevent carbon monoxide poisoning

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Follow these safety tips

  • Install a UL-approved carbon monoxide detector and alarm. These devices measure the amount of carbon monoxide in the air and sound an alarm at certain levels. They should be considered as a backup and not as a replacement for proper use and maintenance of your fuel-burning appliances. Preventing carbon monoxide from becoming a problem in your home is better than relying on an alarm.
  • Have a qualified professional routinely maintain and inspect all heating systems and any fuel-burning appliances annually to ensure they are in good working condition.
  • Have a qualified professional routinely inspect appliance vents and chimney flues annually for blockages, corrosion, cracks or leakage.
  • Never run a vehicle or use unvented fuel-burning equipment in an enclosed space.

Symptoms of carbon monoxide poisoning

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Low levels

Low levels of carbon monoxide exposure can cause shortness of breath, mild nausea, fatigue and mild headaches.

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Moderate levels

Moderate levels can cause headaches, drowsiness, nausea, vomiting, confusion, dizziness or light-headedness.

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Severe cases

Severe cases of carbon monoxide poisoning can result in unconsciousness and death.

Since many of the symptoms of carbon monoxide poisoning are similar to those of the flu, food poisoning or other illnesses, you may not think carbon monoxide poisoning could be the cause.

What to do if you suspect the presence of carbon monoxide


If it is safe to do so, immediately turn off and stop using the gas appliance you suspect is causing the problem. Open the windows to ventilate the area. Do not use the appliance again until it has been determined to be safe by a qualified professional.

Get out of the building and make sure that no one goes back into the building until you are assured that it is safe.

  • Call 911 and seek medical attention if anyone experiences possible carbon monoxide poisoning symptoms.
  • Contact PG&E or a qualified professional to have the appliance inspected.

Recognize signs of a natural gas leak


Please report any signs of a gas leak immediately. Your awareness and action can improve the safety of your home and community.


We add a distinctive, sulfur-like, rotten egg odor so you can detect even small amounts of natural gas. However, DO NOT rely only on your sense of smell to detect the presence of natural gas.


Pay attention to hissing, whistling or roaring sounds coming from underground or from a gas appliance.


Be aware of dirt spraying into the air, continual bubbling in a pond or creek, and dead or dying vegetation in an otherwise moist area.