The term ‘furnace’ is commonly used for any industrial heating device used for the high-temperature processing or burning of material objects. The term ‘oven,’ in contrast, is commonly used for food-processing and -heating devices not intended to burn the food but rather to cook or heat it. Hence, a corpse cremation device is a furnace, while a microwave food-heating device is an oven.
A cremation furnace is a closed space heated by some heat source to an operating temperature of around 800-1000°C, rarely more, in order to completely burn organic tissue of either humans or animals. Such a furnace can have one or more spaces into which the organic tissue, or body, is placed, and which is usually called a ‘retort’ or a ‘muffle.’
Cremation furnaces can have a wide variety of heat sources (wood, coke, oil, gas, electricity). Wood and coke-fired furnaces get their heat from heating spaces separate from the muffle, called a hearth or gas generator, since the incomplete burning of coke and wood in them produces a highly combustible gas rich in carbon monoxide that, when forced hot into the muffle, burns there upon contact with air or oxygen. This technology was widespread in Europe during World War II, and was also the technique used in the crematoria built in German wartime camps.
The term ‘gas oven’ is sometimes used in mainstream literature on the Holocaust. This refers both to cremation furnaces (using the wrong term “oven”) as well as to homicidal gas chambers, but illegitimately mixes the two concepts. Strictly speaking, there is no such thing as a “gas oven” in terms of an oven in which people are gassed to death. Gas chambers and cremation furnaces are two separate devices that, technically speaking, have nothing to do with each other. One can construct a crematorium without any homicidal gassing capability, and one can construct a homicidal gassing facility without any cremation capacity. In fact, given the combustible nature of many gasses claimed to have been used most commonly for homicides in the Holocaust (carbon monoxide and hydrogen cyanide), it would be highly dangerous and foolhardy to construct a homicidal gassing facility using these gasses too close to a cremation facility. And yet, this is precisely what has been claimed of the Germans in case of Crematorium I at the Auschwitz Main Camp.