Furnaces get their name from the Greek word “fornax,” which means oven. The first furnaces were stone or clay structures that used coal and/or wood to create intense heat. These furnaces were primarily used for ceramic work, such as with kilns, and smelting ore to create metal objects, tools, and materials. They are still the primary appliance in industrial metal production. Industrial furnaces are, simply put, cages for raging fires that are hot enough to melt stone, and sometimes, like the image above, look like something built to haunt small children.
Modern day home furnaces tend to run off gas or electricity or induction (a reaction of electricity and metal to create heat). They are much safer and contained than their older counterparts, are the cornerstone for most modern central heating units, producing high amounts of heat that feed into a ventilation system and flow throughout all of the connected rooms.
Small furnaces, usually electrical, are often attached to boilers and water heaters to apply the necessary energy in order to give us hot showers and scalding sink faucets, or even to circulate heat from the boiler to heat our home.