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Sunset Air Blog

Why Do Furnaces Need an Exhaust Flue?

You’ve probably noticed your furnace’s exhaust flue, that pipe that extends away from your ductwork and through the wall to the outside of the house. The concept of an exhaust flue is thousands of years old, it’s the whole reason fireplaces have chimneys. In the context of a modern furnace, however, it may seem odd for the exhaust flue to have so much importance. Most furnaces, depending on their fuel source, don’t produce smoke. So what’s the point? Let’s examine the actual byproducts of today’s furnaces, and why the exhaust flue is necessary to get rid of them.

Incomplete Combustion

Every furnace works by burning some kind of fuel to produce heat, whether it be wood, gas, or oil. Combusting fuel can create heat and energy quite easily, as evidenced by the fact that much of our transportation technology relies on it. Unfortunately, it’s not an efficient process. Combustion is often incomplete, resulting in byproducts of the burnt fuel being created. These byproducts are almost entirely pollutants.

Combustion Byproducts

There are a number of combustion byproducts common to furnaces. The three major ones are carbon monoxide, nitrogen dioxide, and sulfur dioxide. All of these are toxic gases, and should be avoided as much as possible. Unfortunately, carbon monoxide is completely undetectable to human senses. This makes it the most dangerous of the three, as the other two have unpleasant odors that allow them to be more easily avoided.

Carbon monoxide works by displacing the oxygen in a person’s blood stream. In high enough concentrations, this can cause suffocation. Carbon monoxide poisoning is among the most common types of fatal air poisonings on the planet. Common symptoms of exposure include headaches, nausea, dizziness, and fatigue. If you suddenly start experiencing any of these symptoms, especially while the furnace is on, get out of the house and call emergency services. This is the biggest reason why furnaces need an exhaust flue. Without a safe way to vent these byproducts out of the house, they can become trapped and poison the people inside.

If you think your exhaust flue is having issues, call Sunset Air. We provide heating repair services throughout Olympia.

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