Furnace

A furnace is an appliance that generates hot air for all or part of a building, forming the core of a forced-air central heating system. It heats air across a heat exchanger and distributes it through ductwork and blowers to the rooms of a building, most commonly burning natural gas in North America and much of Europe, with liquefied petroleum gas, fuel oil, wood, coal and electric resistance heating also in use elsewhere. Older gas furnaces run at around 80 percent efficiency, while modern high-efficiency condensing furnaces recover latent heat from the exhaust and reach 90 to 98 percent annual fuel utilization efficiency, venting their cooler waste gases through plastic rather than metal flues. This description is adapted from Wikipedia contributors under CC BY-SA 4.0; changes were made. https://creativecommons.org/licenses/by-sa/4.0/