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CO Education

What is Carbon monoxide (CO)?

Carbon monoxide (CO) is an odorless, colorless and tasteless, yet very poisonous gas that can kill quickly and without warning. You cannot see, hear, smell or taste it. Your best protection from carbon monoxide poisoning is to use a carbon monoxide alarm in your home, and educate yourself about carbon monoxide poisoning and its health effects.

What are the most common sources of carbon monoxide?

Please see the house below and click on the various appliances to learn safety tips on how to stop carbon monoxide from invading your home. All fossil fuel powered heaters, water heaters, furnaces and other heaters using wood, coal, oil or other carbon based fuels, gas stoves, gas dryers, both gas and wood fireplaces, cooking equipment such as gas fired ranges, ovens and BBQs, as well as engines such as power tools, snow blowers, gas or gasoline powered grass cutting equipment, trucks, autos and generators can generate carbon monoxide.

Carbon Monoxide (CO) is an odorless, colorless and tasteless -- yet deadly -- gas. It is important to understand what causes it and how to avoid it.

There are precautions that will help avoid exposure to carbon monoxide. Click on one of the CO sources in the house pictured below to learn safety tips on how to stop carbon monoxide from invading your home.

Click on a specific area or appliance on the house...

Click the CO source


If you suspect that CO is contaminating your indoor environment, it is important to act quickly by ventilating the area. If you or a member of your family has flu-like symptoms immediately evacuate the residence and call the gas company, oil company, or fire department from a neighbor's house.


A UL listed carbon monoxide detector is the best protection from this invisible killer. Make sure that the detector or alarm you are using has been fully approved for your intended use. For example, do not use home-use CO alarms in boats or recreational vehicles.

Never unplug or remove the battery to silence a CO detector! There have been many cases of people doing this, then they go back to sleep and never wake up! At the very least, ventilate the area and change the detector's battery. Always assume the worst.
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A chimney that is blocked or clogged due to a bird's nest, leaves, or soot causes combustion byproducts, including CO, to vent into home. Cracked masonry could also cause a blockage. Periodic inspection and cleaning by a chimney sweep helps prevent any difficulties. A screen cap for the top of the chimney to discourage nest building is also a good idea.
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Wood burning and gas powered fireplaces are a common source of carbon monoxide. Leaving the window open a few inches provides for circulation of fresh air while preventing negative pressure buildup/backdrafting which can draw CO and other toxins into the home.

Woodburning Fireplaces: Treated woods, painted wood, and scrap lumber should not be burned in a fireplace. Burn only seasoned firewood. Also, before you start a fire in your fireplace, make sure that the damper is open. Always leave the flue open even if the fire is almost out. Those last smoldering embers produce a high concentration of deadly CO.

Gas log sets: Gas logs or burners produce a lot of CO since the less-efficient, yellow flames are desired for a cozy atmosphere. If you own a ventless fireplace be particularly careful as these appliances vent all combustion byproducts into the room. As the fireplace is run, oxygen is taken from the room to fuel the combustion process. As less oxygen is available, the combustion becomes less efficient and more CO is produced. Some gas log sets use a sensor that shuts down the appliance if oxygen drops to a certain level. The danger is that the appliance can be producing CO even if oxygen isn't depleted from the immediate environment. It is a good idea to look for an appliance with CO safety shutoff device.
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A furnace produces CO because of a mechanical failure as a result of a cracked heat exchanger, flue or burner problems. Incorrect installation, damage caused by basement flooding, and pilot lights can produce CO. Also a clogged or dirty burner can affect the air/fuel mixture resulting in inefficient combustion. Yellow flames and soot accumulation are indications that the furnace needs maintenance. Frequent inspection and regular maintenance of the burner, flue, and chimney should greatly reduce any CO difficulties with this appliance.
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Ventless space heaters are so dangerous that some states including California, Colorado, Massachusetts, Minnesota, Montana, New York, Utah and Washington prohibit their use. Some of these heaters use a sensor that shuts down the appliance if oxygen drops to a certain level. The danger is that the appliance can be producing CO even if oxygen isn't depleted from the immediate environment. Never use a heater inside a house or enclosed structure if the operating instructions tell you not to. Portable heaters and all other unvented appliances vent all the combustion products directly into the interior of the home. It is a good idea to look for appliances with CO safety shutoff devices. Also, leave the window cracked a few inches to allow for circulation of fresh air if you are using a portable heater.
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Gas stoves and range tops are common sources of CO in a house since they are often unvented. Regular cleaning of the range top, oven cavity and burners will alleviate some of the problem. If the burners are dirty and clogged, the fuel air mixture becomes improperly adjusted causing inefficient combustion. Older appliances may have rust or damage to the burner system which may cause CO. Other conditions that could result in CO being produced are improper installation or a faulty appliance. Keep in mind that the exhaust fan that is commonly over the range top is unvented and therefore does not help dissipate CO. The fan provides filtration of grease vapor and soot generated during cooking. The best way to avoid these difficulties is to have regular maintenance done to include cleaning and adjustment of the air/fuel mixture. Also, never warm the house using your natural gas or propane oven.
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A water heater is a potential source of carbon monoxide. The appliance may be faulty as purchased or installed improperly. Basement flooding may have caused damage to make the heater function inefficiently. A clogged burner, blocked vent or even the pilot light can produce CO. Danger signs that CO is being produced include a yellow burner flame and soot buildup. Regular maintenance to ensure air/fuel mixture is adjusted correctly and cleaning of the burner components is recommended to ensure protection from CO poisoning.
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A gas clothes dryer that is purchased faulty or installed incorrectly can be a CO hazard. Damage caused by flooding and exhaust pipes clogged with lint could also cause CO to buildup. The burner can become dirty or clogged and affect the air/fuel mixture resulting in inefficient, CO-producing combustion. Frequent inspection and regular maintenance of the burner are good preventive measures. Also, clean the lint filter after every load of laundry.
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Grills, barbecues and hibachis should never be used indoors, or even inside the garage or on a porch or patio. The smoldering embers of charcoal produce great amounts of CO. Always take care to grill a fair distance away from the windows of your house.
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Probably the greatest CO danger in a residence is a running car in an attached garage, especially if the garage door is closed.


Take these precautions:
Never warm up your car in the garage. Even if the garage door is open, a pocket of CO could form due to temperature variances. Wind can help or hinder dispersion of CO.


Leave the overhead door open for at least a few minutes after you have pulled your car into the garage. The same precautions should be followed when using any combustion appliance including lawnmowers, snow blowers, generators, lawn tools, snow mobiles, motorcycles, etc.


Also, garages should have outside air vents.


Multiple car garages, as are common in apartment houses and condos, are particularly dangerous. A commercial CO detector that activates ventilation controls is recommended for use in these structures.
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Insulation does reduce heat loss and keep those energy bills down but remember you are also cutting down your fresh air supply in your home making combustion less efficient and increasing your CO risk. Creating an energy efficient home could create a negative pressure and cause a backdrafting effect that would draw fumes into your home instead of exhausting them to the exterior. All fuel-burning appliances need to be in good working condition and exhausted to the exterior. Remember that it is always a good idea to make sure there is adequate fresh air for efficient combustion to take place. Crack your window or door. Saving a life is more important than saving a few dollars on your fuel bill.
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Carbon monoxide can be produced by combustion that occurs from fossil fuel burning appliances.  When appliances and vents work properly and there is enough fresh air in your home to allow complete combustion, the trace amounts of CO produced are typically not dangerous. Normally carbon monoxide is safely vented outside your home.

CO levels can rise to dangerous levels if an appliance is installed improperly, if a portable generator is used less than 25 feet from the house or other structure, if a forced air furnace is over 20 years old or if a newer one has been exposed to corrosive materials. The weather sometimes plays a key role in cases of carbon monoxide poisoning.  If you have a pool heater outside and you have not had a serious problem, it does not mean an accident can’t happen.  It only takes a small breeze to blow lethal CO levels into your house. This actually happened to a doctor and his family. In this case the pool heater was installed a year before the deadly accident occurred.  The workers installed a natural gas pool heater and the home was supplied with a propane gas supply. Because of a combination of factors (wind velocity, wind direction, improper installation, length of time in use, building construction, and location of the installed pool heater) a three-year old child was killed and his parents and others were very seriously injured.

Other dangerous CO events can occur when something goes wrong with a good installation, such as birds building a nest or leaves plugging a vent. Appliances can malfunction. A furnace heat exchanger can crack causing carbon monoxide to come into a house instead of going out the vent. Gas logs can be adjusted to create pretty yellow flames, which can increase carbon monoxide emissions dramatically.

Never leave a vehicle running.  Vehicles rank as the second most common cause of fatal accidents from carbon monoxide poisoning. Fire is the number one cause of fatal carbon monoxide accidents. Carbon monoxide is produced when household materials such as drapes, paper, clothing, rugs, furniture and plastics as well as any material that contains carbon burn in a fire.  It is a fast and silent killer. 

You need to be aware that carbon monoxide kills people sitting in a car for prolonged periods of time with the engine running. Some people have died just talking on the phone while sitting in their cars.

Every year police officers, lovers and others succumb to carbon monoxide poisoning in vehicles.  Statistics from the Journal of American Medical Association (a high-quality professional journal that provides careful review before publishing) states  over 5600 deaths  from carbon monoxide poisoning occur every year in the USA.  About 3100 of them are accidental (1550 of those are from fires), 1150 are from engine exhaust and 500 from home appliances.