Fornaciphobia

Fornaciphobia (from Latin fornaci, meaning "furnace") is the fear of furnaces. There are a few reasons for this fear. Some people think that furnaces, especially coal-burning furnaces, shape like monsters that may imaginarily chase after them. Others say furnaces are dangerous as it involves the use of flame inside that could go out of control.

However, the actual fear of the single coals (or charcoals) is "ashkipyrophobia" (from greek "pyro", meaning "fire")