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 combustion chamber, 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 venting systems to ensure proper exhaust of combustion gases. Regular maintenance is essential for optimal performance and safety.