I bought a FIR sauna a few years ago - one of the portable ones that leave your head sticking out of the top. I was unable to get a sweat up so I eventually stopped using it. I can't say I noticed much difference but I was going through a huge emotional upset at the time so I think that my body was not ready for healing. Recently I resurrected it and began slowly. This time I sweated successfully after doing my sun bath, brushing and light exercise (had to stop the excercise). It was pouring out of me this time. However, I began to feel really bad, reverting back to a state of sleeping all day drifting in and out of consciousness and I began to question whether my body was at the stage where it could cope with detoxing at this level. I decided no so I have stopped using it until I am stronger. I think that it is a really good idea to use one for a week or two before one buys and definitely go slowly.