HVAC For Beginners

Carbon Monoxide Sources

The Silent Killer

There can be many carbon monoxide sources in the home. Carbon monoxide is a colorless, odorless, toxic gas. Basically, for any substance to burn, oxygen is required. When there is not enough oxygen available for complete combustion of the fuel, then carbon monoxide is produced. Unvented heaters and other fuel burning appliances can contribute if not adjusted properly. Furnaces, boilers, or water heaters can be a source if their vents are obstructed, leaking, or backdrafting. Backdrafting is where air flows down a vent or chimney instead of rising up and out of the home. This can be caused by an improperly installed unit or by improper combustion air supplied to the home. In older homes this was not as much of a concern because there were significant gaps in the windows, doors, etc. to allow plenty of air to enter from the outside. With modern construction techniques, homes are allowing less of the air from the outside to enter and therefore backdrafting is more common.

**HOT TIP** If you have an older home and make improvements such as new windows, doors, housewrap, etc., you should check the draft of the appliances and introduce combustion air as required.

These sources can be minimized through proper installation and maintenance practices. Other sources can include tobacco smoke, burning candles, and auto exhaust from attached garages.

Effects of exposure to abnormal levels

Abnormal levels of CO can result in carbon monoxide poisoning. This occurs when carboxyhemoglobin is formed in the blood. This inhibits the absorption of oxygen into the blood. CO is the leading cause of accidental poisoning deaths in the U.S. The severity of its effects can depend on age, the very young and the elderly are more severely affected. Overall health can be another factor as those with heart conditions and breathing problems are affected more. The other factors include the level of CO and the amount of time exposed to it. Higher levels and/or prolonged exposure can result in death. It usually occurs without warning. Low levels of CO can cause flu-like symptoms such as headaches, dizziness, nausea, and fatigue.

Detecting abnormal levels

The typical level in a home can be .5 to 5 ppm. Co detectors trigger an alarm based on the accumulation of CO over time. The average detector lasts from 2 to 5 years so check your model. When shopping for a detector, ensure that it has both a low level and a high level alarm. The low level will sound if a low concentration is present over a set period of time. The high level will go off if the CO level is high for a very short period of time. Also, ensure that it has a battery backup. Test it's operation at least every month. Some detectors are combined with smoke detectors for more home protection. The latest models give a loud verbal warning saying whether there is smoke or carbon monoxide. If your alarm sounds, make sure it is not your smoke alarm, they sound a lot alike. Remove everyone from the home and check for symptoms of poisoning. (In many areas, you can call your local fire department for assistance.) Ventilate the home by opening windows. Then, call a local hvac company to check these and other possible carbon monoxide sources.