Carbon Monoxide Hazards

Carbon monoxide has been dubbed”The Silent Killer” for good reason. Carbon monoxide is colorless, odorless and tasteless, remaining virtually undetectable to humans until injury or death occur. According to the U.S. Centers for Disease Control, during the period from 1999–2010, a total of 5,149 deaths from unintentional, non-fire related, carbon monoxide poisoning occurred in the United States, an average of 430 deaths per year. Each year, carbon monoxide poising send approximately 15,000 people to emergency rooms in the U.S. Most carbon monoxide poisonings occur during winter months and the great majority occur in the home. Most carbon monoxide poisonings are preventable.

Carbon monoxide is produced by the incomplete combustion of fuels (e.g., natural gas, propane, oil, gasoline, kerosene, wood, etc,). Common in-home sources include: gas and oil burning appliances; fireplaces; wood stoves; space heaters; automobiles and small engines, such as generators; water heaters; gas clothes dryers; charcoal grills, etc. Malfunctioning, improperly installed and misused equipment pose the greatest hazards to home occupants.

Mechanism and Symptoms of Carbon Monoxide Poisoning

Symptoms of carbon monoxide poisoning

Symptoms of carbon monoxide poisoning

Carbon Monoxide has a very strong affinity for the hemoglobin in red blood cells. The carbon monoxide molecules bind strongly to these blood cells and displace the oxygen molecules that the cells normally transport throughout the body so that very little oxygen is transported to the tissues and brain.  Carbon monoxide is toxic in very small concentrations with the maximum recommended indoor concentration being only 9 PPM. Symptoms may become noticeable in 1-2 hours exposure at only 100 PPM and may become life threatening to some people at only 400 PPM. Carbon monoxide is an insidious, aggressive and potentially fatal toxin, with the young, elderly and those with pre-existing medical conditions at greatest risk.  The good news is that carbon monoxide poisoning is preventable.

Preventing Carbon Monoxide Poisoning

The best way to reduce the hazard of carbon monoxide poisoning is through careful installation and maintenance of fuel burning equipment and exercising safe practices in and around the home. Since carbon monoxide is a byproduct of incomplete combustion of carbon based fuels, it’s important to ensure that fuel burning appliances and equipment are properly installed with adequate combustion air and exhaust venting and that the equipment is properly tuned and adjusted. A poorly maintained and adjusted piece of equipment will produce many times more carbon monoxide that one that is running efficiently. Following are lists of things to do and avoid to reduce the potential for exposure.


  • Purchase and install carbon monoxide detectors in accordance with the manufacturer’s instructions (carbon monoxide is lighter than air so follow instructions for placement carefully). Follow all manufacturer instructions for maintenance and testing, Replace batteries at least annually;

  • Make sure appliances are installed and operated according to the manufacturer’s instructions and applicable building codes. Deficiencies in combustion air provisioning and exhaust venting are surprising common and can present carbon monoxide hazards;

  • Check to make sure that intake and exhaust vents are clear (e.g., free of nesting materials and snow), connections are secure;

  • Have appliances and equipment professionally inspected and serviced regularly;


  • Never service fuel-burning appliances without the proper knowledge, skill and tools. Do not allow unlicensed “handymen” to install or service fuel burning appliances and equipment – use licensed professionals. Always refer to the owner’s manual when performing minor adjustments and when servicing fuel-burning equipment;

  • Run a car or truck inside a garage attached to your house, even if you leave the door open;

  • Use a generator, charcoal grill, camp stove, or other gasoline or charcoal-burning device inside your home, basement, or garage or outside less than 20 feet from a window, door, or intake vent;

  • Heat your house with a gas oven, unvented fuel burning space heater or operate a gas fireplace with a closed damper;

Carbon Monoxide Detectors

Fire and Carbon Monoxide Safety

Fire and Carbon Monoxide Safety

Some states, including Texas, do not require carbon monoxide detectors in homes, even on new construction. If you purchase a home with fuel burning appliances (e.g., furnace, boiler, water heater, stove, oven, gas dryer), fireplace or an attached garage that is not equipped with carbon monoxide detectors, you should install an adequate number in accordance with the manufacturer’s installation instructions immediately upon move-in.

  • CO alarms should be installed in a central location outside each sleeping area and on every level of the home and in other locations where required by applicable laws, codes or standards. For the best protection, interconnect all CO alarms throughout the home. When one sounds, they all sound;

  • Test CO alarms at least once a month. Replace them according to the manufacturer’s instruction. Replace batteries at least annually;

  • If the CO alarm sounds, immediately move to a fresh air location outdoors or by an open window or door. Make sure everyone inside the home is accounted for. Call for help from a fresh air location and stay there until emergency personnel;

Your Home Inspection and Carbon Monoxide Hazards

As of this writing, the Texas Real Estate Commission Standard of Practice (SOP) for home inspections directly addresses carbon monoxide only as it pertains to inspecting and testing installed carbon monoxide detectors. There is no requirement to report the absence of carbon monoxide detectors in a home (note: it is our practice to report the absence of visible carbon monoxide detectors in homes with fuel burning appliances or attached garages). The Texas SOP addresses carbon monoxide detectors as follows.

22 TAC §535.229 (b)

(1) The inspector shall:

(A) manually test the installed and accessible smoke and carbon monoxide alarms;

(C) report as Deficient:

(vi) deficiencies in:

(V) smoke and carbon monoxide alarms;

Your home inspector will also be performing visual inspections of the fuel burning appliances and equipment for conditions which may present carbon monoxide hazards. When HomeCert inspects theses systems we pay close attention to the following common deficiencies which can present carbon monoxide hazards:

  • Adequate combustion air – We see this deficiency most often associated with water heaters installed in small rooms, especially laundry rooms with clothes dryers;

  • Proper exhaust venting, including proper configuration, secure attachment to the appliance, secure connection of vent sections, adequate height, adequate clearance to obstructions, proper material, proper termination, etc.

  • Indications of performance issues such as flame roll out, improper flame color, soot accumulation, etc.

Don’t stop yet

Don’t forget that your family home safety plan should also include smoke alarms, fire extinguishers and a family escape plan. We’ll cover these topics in other articles.