RMT:
SHC seems to be composed of two phases. The first is an endothermic, phase in which the molecules of the body are broken down into their constituent atoms. The gases (hydrogen, oxygen ) rise, and the atomic carbon is uplifted along with them.
The second phase, which need not occur, involves an an open flame. This ignites the gases outside the region of influence, which burn with a bluish flame (indicative of burning hydrogen). It also produces heat.This is an exothermic phase.
The region of influence seems to be like a field centered on the body. Anything in this field--a chair, carpet, et cetera) is also reduced. In the Mary Reeser case (the St. Petersburg widow) an intact and undamaged foot in a black satin slipper remained untouched while almost all of the rest of her body, a circular hole in a carpet laid on a slab floor, and her chair were consumed.Neighbors said Mrs. Reeser was in the habit of stretching out her troublesome leg on a hassock. I recently saw an internet photo (although where I cannot recall) of what probably was a criminologist's photo of an undamaged male leg and shoe which was 'burned off' at the knee, of another case.
The walls of the Reeser apartment were covered with a greasy black soot (atomic carbon)and the plastic electrical outlet covers were melted above a certain level--so it was a slow fire (she was a smoker which accounts for the external flame).
In some earlier witnessed accounts it was said that water not only failed to extinguish the flames, but added to their intensity--which is what one would expect if it were being disassociated.
There is also the suggestion of chemical (carbon monoxide or alcohol) poisoning, which may mean that regions of the brain were affected.There don't seem to be any cases of animals being so consumed.
PB.