Welcome and thankyou for your concern for the caves! A fashionable photographer recently scorched one of the Arches in Arches Park Utah. He didn't like the "natural lighting!" I can't really say anything definitive about Indian procedures. If a cave was utilized, it was for concealment during times of hostilities, and the fire would be deep in the cave and likely as not a small "squaw fire" to avoid detection. In a survival situation you will want the fire VERY visable, so a placement near the mouth is adviseable. This likely will produce a decent draft, much like a "Rumford" fireplace. Caves have their own dangers( not cave bears). They are prime areas for a lovely illness called Valley Fever( coccidiodomycosis), from a spore found in western soils. Anyone who comes down with a severe respiratory illness out of season, or after exposure to dust or winds should be tested! Many doctors still miss this ailment. The periodic outbreak of hantavirus is also a concern. I avoid caves out of consideration for their spiritual use. But if I need to hole up, a bit of corn meal or tobacco may get the local dieties on my side( while trickster coyote laughs at me for being so stupid.) Any more thoughts Hikerdon?