I suppose the antithesis of that is the tee pee with the fire ring in the middle and a smoke hole above. Down in New Mexico I saw round rooms maybe 8? feet deep and 12? feet in diameter - at Indian ruins. There was another small round hole in the floor near the wall "where the spirits could come up from the underworld", and it is presumed that the whole thing was covered with a wooden roof, and that the inhabitants had come together in said underground hole and lit a fire in the smaller hole. I question whether carbon monoxide is a problem in wood fires. However I bring this up say that fire inside is a pretty ancient idea, AND apparently you can even live in a hole with a fire.

However Bill - what are the weight trade offs?
Jim