A blast furnace is a structure composed of several parts capable of smelting metal ores for industrial production of metals. These generally consist of a central chimney-like furnace with several supporting structures around it, including a diagonal belt or elevator to feed ore and fuel into the top of the furnace. Air is blown in through the bottom, and materials are separated inside, leaving molten metal and slag. Component parts include several ducts, pots, stoves, and ovens.

The furnace and its feeding, air-supply, and material-handling components form an integrated industrial structure. An ordinary building that merely encloses machinery has a different form.

Ore and fuel enter above, while the air supply supports the smelting process below. The definition covers metal-ore smelting without restricting the output to a single metal.