How Do Furnaces Work?

Powered by either natural gas or propane, a furnaces is an effective way to heat your home during the winter. A furnace generates warm air by burning fuel and then distributing that warm air throughout your home. Whether it runs on propane or natural gas, a furnace works in essentially the same way. Here, we will explain how a furnace works to help you to get ready for the coming cold season.


Older models use a pilot light to ignite the fuel when it is time to produce heat. A small flow of fuel is supplied by the regulator which ensures that the flame burns continuously so that it is always ready to use. Modern furnaces utilize a “glow stick” made from silicone nitrate to ignite the fuel. This makes modern furnaces much safer to use than older ones.

The Combustion Chamber

Gases mix with air inside the combustion chamber where fuel can be safely ignited to produce heated air. The ignition device, whether a pilot light or glow stick, ignites the mixture of air and fuel.

Your Furnaces Heat Exchanger

Mounted directly above the combustion chamber, the heat exchanger is designed to absorb as much heat from the combustion chamber as possible. Once the air reaches the exchanger, it is heated almost instantly. Once the heating system detects that the air is at the desired temperature, it is moved into the duct system and distributed into the home.

Gases and Exhaust

Carbon monoxide is one of several harmful gases created in the combustion process. Modern furnaces are specially equipped to utilize all of the remaining heat energy in these exhaust gases before venting them safely outdoors.

Furnace Plenum

As warm air is distributed through your home, cold air is diverted back into the furnace where it is collected in a unit called the plenum. The plenum sits next to the heat exchanger and is the last stop for the air before it is filtered and reheated.

Reliable Heating Services in Frederick, MD

To learn more about furnaces, how they function, and what options are right for you, get in touch with the HVAC pros at Dave’s Cooling & Heating. With decades of cumulative experience, our Frederick heating contractors proudly serve  the heating and cooling needs of Maryland for over 12 years. Call today for an estimate. Our HVAC team is standing by to answer your questions.

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