Carbon Monoxide (CO) in Your Home

Carbon monoxide (CO) is a poisonous gas you cannot see or smell. It is produced when liquid, solid or gas fuel is burned—such as natural gas, propane, oil, charcoal, wood and wood pellets. Dangerous levels can build up quickly in your home, garage, or other enclosed areas. CO poisoning is more often a problem in the colder months since that is when Vermonters burn fuel to keep warm and their homes are closed up.

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Watch the video below to learn how to lower your risk of CO poisoning.

What are possible sources of CO?

CO is found in the fumes of any fuel-burning vehicle, appliance, tool, device or equipment. CO can build up in homes, garages or other places that do not have a good flow of fresh air.

Common examples of CO sources include:

  • Fuel-fired furnaces or boilers, woodstoves or fireplaces
  • Cars, trucks, snowmobiles and other vehicles
  • Lawnmowers, snow blowers and other gasoline-powered yard equipment
  • Generators
  • Charcoal and gas barbeque grills
  • Hot water heaters, clothes dryers and refrigerators that use gas or liquid fuel
  • Gas stoves or ovens, especially those with pilot lights
  • Space heaters with pilot lights (e.g. kerosene heaters)
  • Tobacco smoke
  • Stoves, lanterns and heaters for outdoor activities, like camping or ice fishing
What are the signs and symptoms of CO poisoning?

The most common symptoms of CO poisoning can be confused with “flu-like” symptoms—such as headache, dizziness, weakness, upset stomach and vomiting. It can also cause sleepiness, blurred vision, ringing in the ears, breathing problems, and confusion. Because CO poisoning is more common in the colder months when colds and flu are common, you might mistake CO poisoning for a cold or flu.

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

Breathing low levels of CO over a few hours can be just as harmful as breathing high levels for a few minutes. If symptoms go away when you leave your home, but come back when you return, there may be a CO problem in your home. Pets will also suffer these symptoms and can serve as a warning.

Go outside immediately to get fresh air, then dial 9-1-1 if:

  • The CO alarm goes off.
  • You suspect CO poisoning and you or someone else is experiencing these symptoms.
Who is at risk for CO poisoning?

Each year hundreds of people in the U.S. die from CO poisoning, and thousands are sent to the emergency room.

CO lowers the body’s ability to carry oxygen to vital organs such as the heart and brain. In general, the more CO a person breathes in, the more serious the damage that occurs. Older adults, young children, babies, unborn babies, and people with anemia or heart or lung problems are more sensitive to the effects of CO. During strenuous exercise, people are also more sensitive to the effects of CO.

Can CO poisoning be prevented?

Yes, CO poisoning is preventable.

Having a working CO alarm is the only way to know if CO is present. Install a CO alarm with a battery backup near all sleeping areas in your home. Replace the battery when you change the time on your clocks each spring and fall, and test your CO alarm monthly. Read more about CO alarms in the section below.

It’s also important to have everything that uses fuel in your home inspected and serviced by a qualified professional every year. The service technician should have a safety focus. Not only will this lower the risk of CO poisoning but will also lower the risk of chimney fires and the need for costly repairs. It will also improve energy efficiency and indoor air quality. Search a list of Vermont-certified technicians

Have these inspected and serviced every year:

  • Furnace and boiler
  • Hot water heater, gas stove, clothes dryer or other fuel-burning appliance
  • Wood stove, stovepipes and venting systems
  • Fireplaces
  • Chimneys

Here are some other tips to keep you and your family safe:

  • Make sure fuel-burning appliances or equipment vent outside and the pipes are tightly joined and not cracked or rusty.
  • Do not use a stove or fireplace that is not vented or may be clogged.  
  • Clear snow, ice and plants away from any outside vents of fuel-burning equipment.
  • Use generators outside only and more than 20 feet away from any window, door or vent. Never use a generator inside your home, basement, garage or enclosed structure. See "How do I run my generator safely?" to learn more.
  • Never use a charcoal grill, camp stove or other fuel-burning devices inside a home, basement, garage, crawlspace, near a window, in a tent, or in any partially enclosed area.
  • Never use a gas cooking range to heat your home.
  • Never run a car or truck inside a garage attached to your house, even if the garage door is left open. Be aware that remote car starters may turn on a vehicle by accident. See "How can I prevent CO poisoning in my garage?" to learn more.

Go outside immediately to get fresh air, then dial 9-1-1 if:

  • The CO alarm goes off.
  • You suspect CO poisoning and you or someone else is feeling dizzy, light-headed or nauseous.
How can I prevent CO poisoning in my garage?

To safely warm up your car in the cold weather, start the car and remove it from the garage immediately. Leaving the garage door open does not keep CO from building up. Be sure the exhaust pipe is not covered with snow when warming up a vehicle, as this can cause CO to build up inside the car.

Snow blowers, lawn mowers, leaf blowers, and other gas-powered equipment are other possible sources of CO in your garage. Test and service these appliances outdoors, before the cold weather hits. Be sure to use this equipment outdoors and away from doors, windows and vents. Store all fuel outside of living areas.

Here are more tips to stay safe:

  • Have a mechanic inspect the exhaust system of your car or truck annually. Small leaks can cause CO to build up inside the car.
  • Open vents or windows to make sure air is moving if you open a tailgate.
  • Never run your vehicle inside a garage attached to a house even with the garage door open.
  • Be aware of keyless ignition systems and remote starters that can make it easy to turn a car on, or leave it on, by accident.
How do I run my generator safely?

If your power goes out and you need to use a generator, there are several things you can do to prevent CO poisoning as well as electric shock, electrocution, fire and burns.

  • Read and follow the labels and owner's manual.
  • Use generators outside only, in well-ventilated areas, and at least 20 feet away from all doors, windows and vents.
  • Do not use generators in attached garages, basements, or crawlspaces.
  • Direct exhaust away from buildings and make sure it is not upwind from doors, windows and vents.
  • Use a heavy-duty, outdoor-rated extension cord that is 20 feet or longer. Make sure the cord’s wattage is more than the total wattage of all the appliances that will be connected. Replace the cord if it is damaged.
  • Plug items directly into the generator or extension cord. Do not plug the generator into a wall outlet (“backfeeding”) since this could cause utility workers to be electrocuted. Have a qualified electrician install a transfer switch if the generator will be connected to your home’s wiring.
  • Turn off generators and allow to cool before refueling.
  • Store fuel in appropriate containers that are labeled, and store outside of living areas.
  • Use the generator in dry conditions to prevent electrocution. If you have to use it in wet conditions, cover the generator with an open, canopy-like structure and use it on a flat, dry surface.
  • Dry your hands before touching a generator.

co alarms

CO alarms measure the amount of CO in the air and sound an alarm when the CO level is dangerous. Vermont law requires CO alarms in all buildings where people sleep. In a 2018 survey, 36% of Vermont homes did not have a working CO alarm or it was expired.

What type of CO alarm should I install?

There are many types of CO alarms. Some are plug-in, battery operated, electric-powered, and some have two features. In some cases, your smoke alarm may also have a CO alarm.

It is best to choose one that is electric powered with a battery backup and has the Underwriters Laboratory (UL) standard 2034 certification.

Where do I install a CO alarm?

Install at least one CO alarm on each level of your home. Locate it on a wall or ceiling, depending on the manufacturer’s instructions. Make sure there is one located near each sleeping area of the home.

Do I need to replace my CO alarm?

CO alarms wear out. They need to be replaced about every five years. Check the expiration date on your alarm and replace it once it expires. Newer alarms have fewer false alarms.

What do I do if the CO alarm goes off?

If your CO alarm goes off, go outside immediately to get fresh air, then call 9-1-1. Tell the emergency responders that you suspect CO poisoning if you or anyone else has symptoms (like headaches or nausea). Make sure you get everyone out of the building, especially if they are unconscious or not breathing, and pets too.

Make sure that no one goes back into the home until you know it is safe. Have your home checked by your local fire department to find the source of the CO.

Be sure to fix the CO problem as soon as you can. If you are a tenant and need help talking to your landlord, contact your town health officer.