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A-Avis Home Services Plumbing, Heating & Air Conditioning, Inc. Blog

How Does a Gas Furnace Work?

Gas burning furnaces are among the most popular home heating systems on the market today. Many homeowners choose them because they are relatively cheap, easy to maintain and operate, and easy to replace if necessary. What a lot of homeowners don’t know, however, is how a gas furnace actually operates. Let us walk you through the operation of a gas furnace, to help you know your system better.

Pilot Light

The pilot light is a continuously burning flame under your furnace. It is supplied by its own gas line, controlled by a heat sensor called a “thermocouple.” When your thermostat orders the furnace to turn on, the pilot light ignites the burners that serve to keep the furnace going.


The burners are the main sources of heat for your furnace, while the furnace is running, the burners generate the heat that flows through the heat exchanger and warms the air being circulated. The burners are ignited by the pilot light, but stay lit by consuming a steady flow of natural gas from the gas line running into the furnace.

The Heat Exchanger

The heat exchanger is a long, winding tube that extends from the burners to the exhaust flue. As the heat from the burners rises through the heat exchanger, it radiates through it to warm the air passing over the outside of the tube. The toxic combustion gases that are byproducts of the burning process move through the tube to the exhaust flue, where they are harmlessly vented outside.

The Air Filter

The air filter is a fibrous mesh stretched over a plastic or metal framework, which is then inserted in the furnace return duct. This part is responsible for filtering out all the airborne contaminants, like dust and dander, which could buildup and damage the furnace. This part must be cleaned or replaced every few months, as it becomes clogged with debris over time.

So there you have it, a very basic outline of how your gas furnace operates. If you’d like to know more about the inner workings of your heating system, call Avis Plumbing, Heating and Air. We offer professional heating services throughout Riverside.

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