I was surprised to see a thread about human spontaneous combustion in the trash. Not that it was not trash but that no one had mentioned the perfectly reasonable explanation of the purported cases of "spontaneous Human combustion".
The truth is that a human body, particularly a somewhat corpulent human body, will burn. Now it will not burst into flame by itself. Also a live human will not burn. A dead human body will however, under some circumstances, support combustion. What is needed is a dead person, some wicking matterial and a source of ignition. The ideal case would be an overweight smoker with a bad heart. He has a cardiac arrest while seated in his favorite uplostered chair and and drops his lit pipe or cigar into the space between his leg and the arm of the chair. The smoldering fire melts body fat which wicks into the surrounding fabric and sustains a small steady flame. This small fire can over hours of time consume most of the flesh on the body. This produces the gruesome chared corpse sitting in an unburned room which is the principle evidence for the "spontaneous human combustion" cult.