from my understanding and experience, the following is true for a traditionally-constructed and properly carried out sweat lodge or temazcal (which are 2 different things): there will be water vapor, which may be heavy, but it should not have smoke at all.
Anyone with more knowledge, feel free to correct me on this.
I may have been wrong about this WRT the temazcal actually. I'm not sure it came across in my original post that my experience is very limited! (Someone would have had to read my other posts to know that; sorry for not making it more clear.)
I noticed that some research coming out of investigation into cardiovascular health in rural Guatemala, including
a couple of
recent studies published in 2011, indicated that depending on the construction (specifically the venting) of the temazcal, significant and risky CO
2 exposure can occur. This being a small, new body of research, and me not being a scientist, I won't try to interpret it, except to say that I was wrong to make a blanket statement that the traditionally-constructed temazcal would not produce wood smoke exposure. (Well, to be clearer, it seems this research is making the argument that the temazcal design of many rural Maya communities of today, which is what we on this site would term "traditional," while indeed passed on generationally, has diverged over the last several hundred years from a tradition seen in archaeological sites, which did originally have venting of the smoke.)
A note on my personal take on this kind of stuff: There have been
cases where the measurement instruments in badly-designed epidemiological research ("
safari science") have been wildly inaccurate, so I always try to follow topics for a while and see what develops, rather than making automatic assumptions out of one or a small number of studies. I will be keeping my eye on this one.