Smelters are industrial facilities that are used to treat metal ores or concentrates with heat, carbon, and oxygen in order to produce a crude-metal product, which is then sent to a refinery to manufacture pure metals.

In many cases, smelters process sulfide minerals, which yield gaseous sulfur dioxide, a significant waste product. Other smelters, including some that process iron ores, do not treat sulfide minerals. Similarly, secondary smelters used for recycling metal products, such as used automobile batteries, do not emit sulfur dioxide. However, all smelters emit metal particulates to the environment, and unless this is prevented by pollution control devices, these emissions can cause substantial environmental damages.

The earliest large industrial smelting technique involved the oxidation of sulfide ores using roast beds, which were heaps of ore piled upon wood. The heaps were ignited in order to oxidize the sulfide-sulfur to sulfur dioxide, thereby increasing the concentration...