Fennekin are often considered to barely count as fire pokemon, because instead of creating fire from ordinary foods in their stomach, or having a never-ending fire burning on the outside of their body, Fennekin must devour materials which humans can just as easily ignite or their fire will not burn. Fennekin have never been used like Charmander as a makeshift heat source; instead, their trainers must procure for them a steady diet of wood, coal, or other flammable materials.
While a source of frustration for trainers, this weakness has turned Fennekin into a scientific boon. Fennekin are a natural furnace, and far more portable, less accident-prone (especially in a laboratory setting), and give far more consistent results with one another than real furnaces do. For this reason, they have long been used to figure out the energy content of various fuels, in order to determine whether burning them could improve efficiency, or indeed if it was even practical. Fennekin degrees are used as a unit of measurement in Kalos, although the concept has failed to catch on elsewhere, owing primarily to a lack of local Fennekin.
Although some of the fuels in these experiments are too toxic for industrial use, let alone human consumption, and a few tragic accidents in which Fennekin overheated so much that they boiled their observers while expelling fuel from their ears, every Fennekin involved in these experiments has walked away unharmed. This has not, however, led to further experiments to explain Fennekin's high survivability rate. With most researchers fearful of harming their adorable, beloved pokemon – or just fearful that anything which could do so would create a far greater catastrophe = science has thus far taken credence in the old tales about Fennekin and its evolutions, and chalked their resilience up to magic.