Carol

Oxidation is always occurring, but at a slow rate ( rust). In the presence of heat and oxygen, it will proceed at a more rapid rate. In the case of a fire, once started, if the heat is held in ( insulated) the temperature can get much higher than the temperature of the same substances in the open: ie, if a kerosine flame is at ( made up number) 500 degrees, then it can heat up a furnace ( such as a kiln) to 1000 degrees, since the heat is contained- insulated- by the wall of the kiln ( which are usually gypsum, the material in wallboard)

Basic chemistry, which is why the aliens had to use special devices just to pull this off so you would think it was an inside job.