A gas furnace is a heating system that uses natural gas or propane to generate warmth for homes and buildings. It works by igniting gas in a burner, which heats air that is then circulated through ducts by a blower. This process efficiently warms indoor spaces during cold weather. Gas furnaces are popular for their effectiveness and relatively low operating costs compared to electric heating systems. They typically include safety features like automatic shut-off valves and thermostats to maintain desired temperatures. Regular maintenance is essential to ensure safe and efficient operation of the furnace.