Carbon Monoxide Poisoning Basics

At a glance

  • Carbon monoxide (CO) is an odorless, colorless gas that can cause sudden illness and death if inhaled.
  • Find quick facts about CO poisoning and what can be done to prevent it.

What it is

Carbon monoxide (CO) is an odorless, colorless gas that kills without warning. It claims the lives of hundreds of people every year and makes thousands more ill.

Many household items including gas- and oil-burning furnaces, portable generators, and charcoal grills produce this poison gas.


The most common symptoms of CO poisoning are headache, dizziness, weakness, upset stomach, vomiting, chest pain, and confusion. CO symptoms are often described as “flu-like.”

If you breathe in a lot of CO, it can make you pass out or kill you. People who are sleeping or drunk can die from CO poisoning before they have symptoms.

Risk factors

Everyone is at risk for CO poisoning. Infants, the elderly, and people with chronic heart disease, anemia, or breathing problems are more likely to get sick from CO.

Each year, more than 400 Americans die from unintentional CO poisoning not linked to fires, more than 100,000 visit the emergency room, and more than 14,000 are hospitalized.

Reducing risk

CO is found in fumes produced any time you burn fuel in cars or trucks, small engines, stoves, lanterns, grills, fireplaces, gas ranges, or furnaces. CO can build up indoors and poison people and animals who breathe it. However, you can reduce your risk of CO poisoning with a few small steps.

CO detectors

Carbon monoxide detector
Replace your CO detector every 5 years

Install battery-operated or battery back-up CO detectors near every sleeping area in your home.

Check CO detector batteries when you change the time on your clocks each spring and fall to be sure they are functioning properly.

Consider buying a detector with a digital readout. This type of detector can tell you the highest level of CO concentration in your home, in addition to sounding an alarm.

Replace your CO detector every 5 years.

Oil and gas furnaces and other household appliances

Technician servicing furnace
Have your heating system serviced annually

Have your heating system, water heater, and any other gas, oil, or coal burning appliances serviced by a qualified technician every year.

Make sure your gas appliances are vented properly. Horizontal vent pipes for appliances, such as a water heater, should go up slightly as they go toward outdoors, as shown below. This prevents CO from leaking if the joints or pipes aren't fitted tightly.

When you buy gas equipment, buy only equipment carrying the seal of a national testing agency, such as Underwriters' Laboratories.

If you smell an odor from your gas refrigerator, have an expert service it. An odor from your gas refrigerator can mean it could be leaking CO.

Never heat your house with a gas oven. Don't cook or burn anything on a stove or fireplace that isn't vented.

Diagram of safe heating equipment to chimney connection.
Horizontal vent pipes for appliances, such as a water heater, should go up slightly as they go toward outdoors

Chimneys, charcoal, and portable appliances

Have your chimney checked or cleaned every year. Chimneys can be blocked by debris, which can cause CO to build up inside your home or cabin.

Never burn charcoal indoors. Burning charcoal - red, gray, black, or white - gives off CO.

Never use a portable gas camp stove indoors. Do not use portable flameless chemical heaters indoors.

Portable generators

Diagram of safe placement of portable generators.
Operate your generator in the safest place to avoid CO poisoning

Never use a generator inside your home or garage, even if doors and windows are open.

Only use generators outside, more than 20 feet away from your home, doors, and windows.

When using a generator, use a battery-powered or battery backup CO detector in your home.

If you have a had a poisoning incident related to any generator...‎

Let the Consumer Product Safety Commission know!


Have a mechanic check the exhaust system of your car or truck every year. A small leak in the exhaust system can lead to a buildup of CO inside the car.

Never run your car or truck inside a garage that is attached to a house, even with the garage door open. Always open the door to a detached garage to let in fresh air when you run a car or truck inside.

If you drive a car or SUV with a tailgate, when you open the tailgate open the vents or windows to make sure air is moving through. If only the tailgate is open, CO from the exhaust will be pulled into the car or SUV.