Central heating differs from space heating in that the heat generation occurs in one place, such as a furnace room or basement in a house or a mechanical room in a large building (though not necessarily at the geometrically “central” point). The heat is distributed throughout the building, typically by forced-air through ductwork, by water circulating through pipes, or by steam fed through pipes. The most common method of heat generation involves the combustion of fossil fuel in a furnace or boiler.
In much of the temperate climate zone, most detached housing has had central heating installed since before the Second World War. Where coal was readily available (i.e. the Anthracite coal region in northeast Pennsylvania) coal-fired steam or hot water systems were common. In more recent times, these have been updated to use fuel oil or gas as the source of combustion, eliminating the need for a large coal storage bin near the boiler and the need to remove and discard ashes after the coal is burned. Coal-fired systems are now mostly reserved for larger buildings.
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