I haven't yet read the article (I will) but to me the "Fire of Hell" refers to a preternatural analogue of fire in this physical world. It is not really a metaphor -- it is actual hellfire as it exists in that demonic space where the physical laws of this world are not applicable. Those souls who have had the favor or misfortune of visiting hell or purgatory in near death experiences describe it as hot, burning, consuming...well....fire. The difference seems to be that corporal tissue is continuously replenished, only to burn again.
but is it a dry heat?