A muffle furnace (sometimes, retort furnace) in historical usage is a furnace in which the subject material is isolated from the fuel and all of the products of combustion including gases and flying ash.[1] After the development of high-temperature electric heating elements and widespread electrification in developed countries, new muffle furnaces quickly moved to electric designs. They are also used in many research facilities, for example by chemists in order to determine what proportion of a sample is non-combustible and non-volatile.