Hmmm...I can only answer this qualitatively, but the fire shelters that wildland firefighters carry are designed to reflect radiant heat and create a cooler air space to help protect the lung tissues. This refers to the portable shake-and-bake fire shelter, not the fire bunker in the previous post. Fire guys (and gals) are trained to lay in the shelter face down with their face in cooler earth.

"They found in testing fire shelters set up in prescribed burns that air temperatures increase at a rate of 9ºF. per inch rise above the floor of the shelter." (link below, and please note that was for a prescribed burn, not a firestorm)

A dry bandana may be used to help screen out smoke, dust, etc...but it has to be dry since steam carries a lot more heat than dry air. What is stressed over and over again in training is that the fire shelter's only purpose is to create a cooler air space to protect the lung tissues. Yes, I repeat myself. Yes, it's that important.


"If you go into a steam room, 130 degrees is about as hot as you can stand it," says Putnam. "In a dry sauna, though, you can take 180 degrees. You can tolerate hot dry air better than moist air." (not talking about lung tissues though)

The single breath deal is when you get a gasp of something not-nice (smoke, superheated air, whatever), that's going to trigger a gag reflex...and so you inhale again...and again...

There's a fair amount of literature out there about the environmental and physiological effects of wild land fire. Google "fire shelter" and pay attention to any research coming out of Missoula.

http://wildfirenews.com/fire/articles/ted.html

Found the fire shelter instructions:

http://www.nwcg.gov/pms/pubs/fireshelt01.pdf