Heat

It was blistering, the heat, not from any source, permeated the entire airspace. The air was thick, like inside an oven, a sauna. Each breath, a suffocating intake of fire-hot miasma, accompanied by clawing desperation to grasp air. Air unladen with the crushing heat. Air cool like flowing water, not freshly spewed magma. Air with oxygen, not saturated with boiling steam. 

The heat seeped in every pore, ran along every surface. Sweat and the moist air forming a laminar layer, bounding in the intruding heat. Inside and out, each surface burned and blistered, the fire slowly disintegrating the body into ashes.