Weber County
Brigham City
Salt Lake


A gas furnace contains a variety of components intended to ensure safety and reliability, but few are as critical to its operation as the heat exchanger and exhaust flue. These seemingly simple pieces of equipment play a dual role in both heating your home and safely expelling exhaust gases.

Along with the rest of the furnace's exhaust system, the heat exchanger allows you to utilize the energy of natural gas without exposure to dangerous combustion byproducts. To understand why these components are so essential, read this blog for a quick lesson in chemistry and a brief tour through your furnace's exhaust stream. If you have any questions, reach out to a qualified HVAC professional for help.

Learn the Chemistry of Combustion

Your furnace provides heat to your home through a relatively simple chemical reaction. The natural gas that supplies your furnace or other appliances consists of a blend of chemicals, though it’s mostly methane. Like any fossil fuel, methane is highly combustible in the presence of oxygen.

When natural gas combusts, the reaction between methane fuel and oxygen produces several harmful byproducts in addition to heat. Although carbon dioxide (CO2) makes up the vast majority of the exhaust stream, the relatively small quantities of carbon monoxide (CO) are the more significant concern. Even tiny amounts of carbon monoxide pose a critical health hazard.

Fortunately, modern furnace designs can safely account for the byproducts they produce.

Follow the Exhaust Stream

To protect the air in your home from exhaust gases, combustion in your furnace takes place within a sealed chamber. This approach locks away harmful chemicals, but it also means that the furnace does not directly heat the air in your house. Instead, the exhaust stream traps that heat along with the carbon monoxide and other pollutants.

This is where the heat exchanger enters into the picture. Your furnace's heat exchanger is essentially a set of metal coils or tubes that extracts energy from the exhaust gases. As the gases pass through the heat exchanger, energy (in the form of heat) is transferred to the surrounding air. The furnace's blower then distributes this clean, warm air to the rest of your home.

After passing through the heat exchanger, the cooled gases continue to move through the exhaust flue and safely into the outside atmosphere. Some furnaces will do a better job than others at capturing the heat before it escapes with the gases, while others will be more inefficient. To save money and power, consider upgrading to a more efficient furnace model.

Keep Your Air Clean

Although the purpose of your heat exchanger is to contain and extract energy from warm gases, it can only absorb a limited amount of heat. A variety of conditions can cause your heat exchanger to overheat, potentially leading to small cracks in the casing. Over time, these cracks can allow harmful exhaust gases to escape into your home.

Old, corroded flue pipes can also be potential sources of exhaust leaks. In some cases, an improperly installed flue may allow condensation to remain in the pipes, leading to rust and holes. Like a cracked heat exchanger, leaky flue pipes may allow carbon monoxide gas into your home. Detecting problems with a furnace flue is often challenging and requires an experienced eye.

Although cracked heat exchangers and leaky flue pipes are uncommon, they pose enough of a danger to warrant annual inspections by trained professionals. If you're ready to have your heating system inspected, Dick Kearsley Service Center can help you to get the job done. Contact us online to schedule a time and date that is convenient for you.


520 S State, Clearfield, UT 84015

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Mon-Fri: 8:00 am - 5:00 pm

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Sunday: Closed

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Davis/Morgan: 801-773-4836

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