Gas Furnace
Updated
A gas furnace burns natural gas or propane to heat your home. The burners heat a heat exchanger, a blower pushes household air across it, and the warmed air travels through ductwork to every room.
Combustion gases vent outside through a flue and never mix with the air you breathe when everything is working the way it should. Furnace efficiency is measured by AFUE, the percentage of fuel that actually becomes heat in your house. One plain safety note: if you ever smell gas, that is a stop-and-call situation. Leave the house and make the call from outside rather than troubleshooting anything yourself. When one stops heating, furnace repair starts by testing that ignition sequence step by step.
Common Questions
How does a gas furnace heat a house?
Burners light and heat the heat exchanger, and a blower pushes your household air across its hot surface before sending it through the ducts. The air that reaches your rooms never touches the flame. It only picks up heat through the exchanger walls.
What is the difference between an 80% furnace and a high-efficiency furnace?
An 80% furnace sends roughly a fifth of the heat it makes up the flue, while condensing models capture most of that heat before it escapes. The AFUE rating is the number that captures the difference, and it shows up directly on your gas bill.
What should I do if I smell gas near my furnace?
Stop, leave the house, and make the call from outside. Do not flip switches or try to find the source yourself. The same stop-and-call rule applies to a suspected heat exchanger crack. Neither is common, and neither is a wait-and-see situation.
Related Terms
Questions about your heating or cooling?
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