Muffle furnaces are used in the lab for high-temperature applications involving testing of various materials. The ability of these furnaces to achieve extremely high temperatures is integral for many critical industrial applications. By definition, a muffle furnace (also sometimes referred to as a retort furnace) isolates the subject material from the fuel and all of the products of combustion, including gases and flying ash. The units are usually front-loading, box-type construction that are placed or mounted on a bench top in a testing laboratory.