A furnace works by using a fuel source, such as natural gas or electricity, to create heat in a combustion chamber or through heating elements. This generated heat is transferred to a heat exchanger, where it warms up the surrounding air. A blower fan then circulates this heated air through a network of ducts, distributing it to different areas of the building. A thermostat monitors the indoor temperature and signals the furnace to start or stop, ensuring that the desired comfort level is maintained. Safety features are in place to prevent hazards, and regular maintenance is required for efficient and safe operation. Furnaces can use various fuel sources and technologies to achieve heating, making them a common choice for residential and commercial heating needs.