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Carbon Monoxide (CO), the ‘Invisible Killer’

According to the Centers for Disease Control and Prevention an average of 470 CO fatalities occur in the U.S. each year. The U.S. Consumer Product Safety Commission reports about 170 people a year in the U.S. perish from CO produced by non-automotive consumer products. These products include malfunctioning fuel-burning appliances such as furnaces, ranges, water heaters and room heaters; engine-powered equipment such as portable generators; fireplaces; and charcoal that is burned in homes and other enclosed areas.

What is carbon monoxide and where does it come from?

CO, often called the “Invisible Killer,” is a deadly, colorless, odorless, poisonous gas. It is produced by the incomplete burning of various fuels, including coal, wood, charcoal, oil, kerosene, propane, and natural gas. Products and equipment powered by internal combustion engines such as portable generators, cars, lawn mowers, and power washers also produce CO.

What are the symptoms of carbon monoxide poisoning?

Because CO is odorless, colorless, and otherwise undetectable to the human senses, people may not know that they are being exposed. The initial symptoms of low to moderate CO poisoning are similar to the flu (but without the fever). They include:

  • Headache
  • Fatique
  • Shortness of breath
  • Nausea
  • Dizziness

High level CO poisoning results in progressively more severe symptoms, including:

  • Mental Confusion
  • Vomiting
  • Loss of muscular coordination
  • Loss of consciousness
  • Ultimately death

Symptom severity is related to both the CO level and the duration of exposure. For slowly developing residential CO problems, occupants and/or physicians can mistake mild to moderate CO poisoning symptoms for the flu, which sometimes results in tragic deaths. For rapidly developing, high level CO exposures (e.g., associated with use of generators in residential spaces), victims can rapidly become mentally confused, and can lose muscle control without having first experienced milder symptoms; they will likely die if not rescued.

Can I prevent carbon monoxide poisoning?

Yes, you can prevent carbon monoxide poisoning by following these simple steps:

  • Make sure appliances are installed and operated according to the manufacturer's instructions and local building codes. Most appliances should be installed by qualified professionals. Have the heating system professionally inspected and serviced annually to ensure proper operation. The inspector should also check chimneys and flues for blockages, corrosion, partial and complete disconnections, and loose connections.
  • Never service fuel-burning appliances without proper knowledge, skill and tools. Always refer to the owner’s manual when performing minor adjustments or servicing fuel-burning equipment.
  • Never operate a portable generator or any other gasoline engine-powered tool either in or near an enclosed space such as a garage, house, or other building. Even with open doors and windows, these spaces can trap CO and allow it to quickly build to lethal levels.
  • Install a CO detector that meets the requirements of the current UL 2034 safety standard. A CO detector can provide some added protection, but it is no substitute for proper use and upkeep of appliances that can produce CO.
  • Never use portable fuel-burning camping equipment inside a home, garage, and vehicle or tent unless it is specifically designed for use in an enclosed space and provides instructions for safe use in an enclosed area.
  • Never burn charcoal inside a home, garage, vehicle, or tent.
  • Never leave a car running in an attached garage, even with the garage door open.
  • Never use gas appliances such as ranges, ovens, or clothes dryers to heat your home.
  • Never operate unvented fuel-burning appliances in any room where people are sleeping.
  • Do not cover the bottom of natural gas or propane ovens with aluminum foil. Doing so blocks the combustion air flow through the appliance and can produce CO.
  • During home renovations, ensure that appliance vents and chimneys are not blocked by tarps or debris. Make sure appliances are in proper working order when renovations are complete.

How should I install a carbon monoxide detector?

CO detectors should be installed according to the manufacturer's instructions. The United States Consumer Product Safety Commission recommends that one CO detector be installed in the hallway outside the bedrooms in each separate sleeping area of the home. CO detectors may be installed into a plug-in receptacle or high on the wall. Hard wired or plug-in CO detectors should have a battery backup. Avoid locations that are near heating vents or that can be covered by furniture or draperies. CPSC does not recommend installing CO detectors in kitchens or above fuel-burning appliances.

What should I do when the carbon monoxide detector sounds?

Never ignore an alarming CO detector! It is warning you of a potentially deadly hazard. If the alarm signal sounds do not try to find the source of the CO. Follow these steps:

  • Immediately move outside to fresh air.
  • Call your emergency services, fire department, or 911.
  • After calling 911, do a head count to check that all persons are accounted for. DO NOT reenter the premises until the emergency services responders have given you permission. You could lose consciousness and die if you go in the home.
  • If the source of the CO is determined to be a malfunctioning appliance, DO NOT operate that appliance until it has been properly serviced by trained personnel.

If authorities allow you to return to your home, and your detector reactivates within a 24 hour period, repeat steps 1, 2 and 3 and call a qualified appliance technician to investigate for sources of CO from all fuel burning equipment and appliances, and inspect for proper operation of this equipment. If problems are identified during this inspection, have the equipment serviced immediately. Note any combustion equipment not inspected by the technician and consult the manufacturers’ instructions, or contact the manufacturers directly, for more information about CO safety and this equipment. Make sure that motor vehicles are not, and have not been, operating in an attached garage or adjacent to the residence.

How do I maintain my carbon monoxide detectors?

Follow these suggestions for maintaining your CO detectors:

  • Test CO detector at least once a month and replace them if they fail to respond correctly when tested. The sensors in CO detector have a limited life. Replace the CO detector according to manufacturer’s instructions or when the end-of-life signal sounds.
  • Know the difference between the sound of the CO detector and the smoke alarm, and their low-battery signals. If the audible low battery signal sounds, replace the batteries or replace the device. If the CO detector still sounds, get to a fresh air location and call 9-1-1 or the fire department.
  • To keep CO detector working well, follow manufacturer’s instructions for cleaning.

Where can I go for further information?

To have your questions answered and for other general information please contact the Community Risk Reduction Section at (803) 896-5454 or

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Robert Polk, State Fire Marshal
141 Monticello Trail, Columbia, SC 29203
(803) 896-9800 | Office Hours: 8:30 a.m.- 5:00 p.m. | Monday - Friday except State Holidays