Carbon Monoxide and Your Gas Furnace

By Scott Bowen | April 8, 2014

What is carbon monoxide (CO)?

Carbon monoxide (CO) is a poisonous, colorless, odorless, and tasteless gas. Although it has no detectable odor, CO is often mixed with other gases that do have an odor. So, you can inhale carbon monoxide right along with gases that you can smell and not even know that CO is present.

Where is carbon monoxide (CO) found?

CO is a common industrial hazard resulting from the incomplete burning of natural gas and any other material containing carbon such as gasoline, kerosene, oil, propane, coal, or wood. Forges, blast furnaces and coke ovens produce CO, but one of the most common sources of exposure in the workplace is the internal combustion engine. Our focus will be on carbon monoxide produced by an HVAC furnace.

How does a furnace produce carbon monoxide?

Virtually every gas furnace produces some Carbon Monoxide, which is then carried away from your home through the furnace’s venting. A clean, efficiently burning gas furnace produces very small amounts of carbon monoxide, while a dirty, inefficiently burning one can produce larger amounts. Carbon Monoxide is odorless and colorless. It causes flu-like symptoms, disorientation, confusion, and even death.

How to be safe and proactive.

It is highly recommended that you have your furnace cleaned and checked every year. The older the furnace, the more important this service is. Newer gas furnaces are equipped with many features that shut the furnace off when a problem is detected. Older furnaces have no such devices. Over time, furnaces can develop small cracks in the combustion chamber. These cracks may not be visible to the naked eye. It is through these cracks that Carbon Monoxide can leak into your home.

A Thomas Tale:

While on one of our biannual tune up visits for an SEA customer, we came across this rather unsettling heat exchanger (where gas is burned in a furnace):

Our customer had been having headaches, and didn’t know the cause. We found that her heat exchanger had rusted out and left these holes for carbon monoxide to escape into her home. Thankfully, we were able to catch it before any of the symptoms progressed, but it really highlights the importance of checking your gas furnace on a regular basis. We recommend 1-2 inspections per year, as included in our Safety and Efficiency Agreement. If you have a gas furnace that you haven’t had inspected any time in the last year, please be sure to call a certified HVAC contractor to come by and thoroughly inspect your gas furnace to verify there are no holes or cracks in your heat exchanger.