Recently, public attention has focused on the risk of carbon monoxide (or CO) poisoning in the home. The National Fire Protection Association (NFPA) prepared this fact sheet to help people protect themselves and their families against CO poisoning.

What is carbon monoxide?

What are common CO sources in your home?

How to prevent CO poisoning?

What is the effect of exposure to CO?

What is your risk of CO poisoning?

What CO level is dangerous to your health and what are the symptoms of CO poisoning?

How can you protect yourself from CO poisoning?

What are CO detectors?

What type of CO detector should you buy?

How many and where should you install CO detectors?

What causes CO detector nuisance alarms?

What you should do if your CO detector alarms

Safety Tips

Safety Checklist

What is carbon monoxide?

Carbon monoxide (CO) is an invisible, odorless, colorless gas created when fossil fuels (such as gasoline, wood, coal, propane, oil and methane) burn incompletely. In the home, heating and cooking equipment are possible sources of carbon monoxide. Vehicles running in an attached garage could also produce dangerous levels of carbon monoxide.

However, consumers can protect themselves against CO poisoning by maintaining, using, and venting heating and cooking equipment and by being cautious when using vehicles in attached garages.

What are common CO sources in your home?

Fuel burning appliances such as:

Furnaces
Stoves & Ovens
Water Heaters
Dryers
Room/Space Heaters
Fireplaces and Woodstoves
Charcoal Grills
Automobiles

How to prevent CO poisoning?

• Make sure appliances are installed and working according to manufacturer's instructions and local building codes.  Have the heating system (including chimneys and vents) inspected and serviced annually by a professional which includes inspecting for blockages, corrosion, partial and complete disconnections, and loose connections.
• Install CO detectors (see details below)
• Never use gas appliances such as ranges, dryers, or ovens for heating your home.
• Never burn charcoal inside a home, garage, vehicle, or tent.
• Never operate un-vented fuel-burning appliances in any room with closed doors or windows or in any room where people are sleeping.
• Never use portable fuel-burning camping equipment inside a home, garage, vehicle, or tent.
• Never leave a car running in an attached garage, even with the garage door open.

What is the effect of exposure to CO?

CO replaces oxygen in the bloodstream, eventually causing suffocation. Mild CO poisoning feels like the flu, but more serious poisoning leads to difficulty breathing and even death.

Just how sick people get from CO exposure varies greatly from person to person, depending on age, overall health, the concentration of the exposure (measured in parts per million), and the length of exposure. Higher concentrations are dangerous even for a short time.

What CO level is dangerous to your health and what are the symptoms of CO poisoning?

The health effects of CO poisoning depend on the level of CO and length of exposure, as well as each individuals health condition.  The concentration of CO is measured in parts per million (ppm).  The U.S. Environmental Protection Agency estimates that the average levels in homes without gas stoves vary from 0.5 to 5 ppm and levels near properly adjusted gas stoves are often between 5 to 15 ppm.  According to the Consumer Product Safety Commission (CPSC), health effects from exposures to CO levels of approximately 1 to 70 ppm are uncertain, but most people will not experience any symptoms.  Although, some heart patients may experience an increase in chest pain.  As CO levels increase and remain above 70 ppm, symptoms (see below) may become more noticeable.  As CO levels increase above 150 to 200 ppm, disorientation, unconsciousness, and death are possible.  

Symptoms of CO poisoning include:

• Headache
• Nausea
• Fatigue
• Dizziness
• Shortness of breath.
• Sleepiness
• Confusion

In many cases of CO poisoning, these symptoms have been mistaken as the flu.

How can you protect yourself from CO poisoning?

The best defenses against CO poisoning are safe use of vehicles (particularly in attached garages) and proper installation, use and maintenance of household cooking and heating equipment.

You may also want to install CO detectors inside your home to provide early warning of accumulating carbon monoxide. However, a CO detector is no substitute for safe use and maintenance of heating and cooking equipment.

What are CO detectors?

Household carbon monoxide detectors measure how much CO has accumulated. Currently, CO detectors sound an alarm when the concentration of CO in the air corresponds to 10% carboxyhemoglobin level in the blood. Since 10% COHb is at the very low end of CO poisoning, the alarm may sound before people feel particularly sick.

What type of CO detector should you buy?

CO detectors either operate on battery power or directly off your household current, and they use different sensor technologies to sense the levels of CO in your home.  Regardless of the different types of CO detectors, all detectors sold on the market today should conform to minimum sensitivity and alarm characteristics defined and verified by the Underwriters Laboratory (UL).  So the primary guide to selecting a CO detector is to make sure that it is UL listed.  Outside of this, select a CO detector that meets your application requirements and make sure to follow the installation and maintenance (e.g., battery replacement schedule) instructions provided by the manufacturer.

How many and where should you install CO detectors?

It is recommended that a CO detector be placed on each level of your home.  At a minimum, you should have a CO detector located outside and near sleeping areas.  After covering the sleeping areas, the next best location for an additional CO detector is in the area of any major gas burning appliances such as a furnace or water heater.  In general, follow the manufacturers instructions for installation location.  Although CO is about the same weight as air, it is often recommended to place CO detectors high since the CO may be contained in the warm air coming from the combustion appliance.  Also, when installing CO detectors in the areas of major gas burning appliances, do not install the detector within approximately 15 feet of the appliance itself.  Again, follow the manufacturer's instructions.

What causes CO detector nuisance alarms?

Pollution and atmospheric conditions in some areas cause low levels of CO to be present for long periods of time. In fact, these "background" conditions may increase the COHb level to over 10%, causing CO detectors to alarm even though conditions inside the home are not truly hazardous. Treat all CO detector alarms as real, until it has been verified that there is no threat from equipment inside the dwelling.

If you buy CO detectors:

• Select detector(s) listed by a qualified, independent testing laboratory.
• Follow manufacturer's recommendations for placement in your home.
• Call your local fire department non-emergency telephone number. Tell the operator that you have purchased a CO detector and ask what number to call if the CO detector alarms. Be sure you understand whom to call if your detector alarms, and clearly post that number by your telephone(s). Make sure everyone in the household knows the difference between the fire emergency and CO emergency numbers (if there is a difference).
• Test CO detectors at least once a month, following the manufacturer's instructions.
• Replace CO detectors according to the manufacturer's instructions, usually about every two years.
• Battery powered CO detectors may have unique battery packs designed to last approximately two years, compared to batteries used in smoke detectors, which require yearly replacement.

What should you do if the CO detector alarm sounds?

First of all, never ignore an alarm and do not panic!  Although, exposure to high levels of CO over prolonged periods of time can be life threatening, a large number of instances that activate the CO alarm are not life threatening and do not require calling 911.  To determine the need to call 911, ask the following question to everyone in the household.

Does anyone feel sick and experiencing the "flu-like" symptoms of dizziness, nausea, or headaches?

Yes: If the answer to the above question is yes, immediately evacuate the household to a safe location and call the Fire Department at 911.  Leave doors open as you go. Use a neighbor's telephone to report the CO alarm, following the instructions you received from the fire department when you bought the detector. Get immediate medical attention. The best initial treatment for CO exposure is fresh air followed by treatment from a physician.

No:  If the answer to the above question is no, the likelihood of a serious exposure is greatly reduced and calling 911 is not necessary at this time.  Instead, turn off any gas appliances or equipment and open doors and windows to help ventilate your home with fresh air from outside.  After completing this, occupants are urged to contact your local gas utility company (e.g., Quarles at 635-2166) or a qualified heating and ventilating service contractor to inspect your system for possible problems.  Note: If at any time during this process someone in your household experiences "flu-like" symptoms, immediately evacuate the home and call 911.

Additional Information & Links

Consumer Product Safety Commission (CPSC) - Carbon Monoxide Questions and Answers.
U.S. Environmental Protection Agency (EPA) - Sources of Indoor Air Pollution - Carbon Monoxide (CO)
Centers for Disease Control (CDC) - Carbon Monoxide

Safety Tips

If you need to warm up a vehicle, remove it from the garage immediately after starting the ignition. Do not run a vehicle or other fueled engine or motor indoors, even if garage doors are open.

CO from a running vehicle inside an attached garage can get inside the house, even with the garage door open. Normal circulation does not provide enough fresh air to reliably prevent dangerous accumulations inside.

Have your vehicle inspected for exhaust leaks, if you have any symptoms of CO poisoning.

Have fuel burning household heating equipment (fireplaces, furnaces, water heaters, wood stoves, and space or portable heaters) checked every year before cold weather sets in. All chimneys and chimney connectors should be evaluated for proper installation, cracks, blockages or leaks. Make needed repairs before using the equipment. Before enclosing central heating equipment in a smaller room, check with your fuel supplier to ensure that air for proper combustion is provided. When using a fireplace, open the flue for adequate ventilation.

Kerosene heaters are illegal in many states. Always check with local authorities before buying or using one. Open a window slightly whenever using a kerosene heater. Refuel outside, after the device has cooled.

Always use barbecue grills outside if they can produce carbon monoxide. Never use them in the home or garage. When purchasing new heating and cooking equipment, select factory built products approved by an independent testing laboratory. Do not accept damaged equipment. Hire a qualified technician (usually employed by the local oil or gas company) to install the equipment. Ask about and insist that the technician follow applicable fire safety and local building codes. If you purchase an existing home have a qualified technician evaluate the integrity of the heating and cooking systems, as well as the sealed spaces between the garage and house.

When camping, remember to use battery powered heaters and flashlights in tents, trailers and motor homes. Using fossil fuels inside these structures is extremely dangerous. NFPA 501, Standard on Recreational Vehicles, requires the installation of CO detector in recreational vehicles.

Safety Checklist

• Carbon monoxide detectors are not substitutes for smoke detectors. Smoke detectors react to fire by-products, before CO detectors would alarm. Smoke detectors give earlier warning of a fire, providing more time to escape.
• To guard against smoke and fire, be sure that your home has working smoke detectors on every level and just outside of all sleeping areas.
• Know the difference between the sound of the smoke detectors and the sound of the carbon monoxide detector.
• Have a home evacuation plan for any home emergency and practice the plan with all members of the household.

(Source: National Fire Protection Association)