I've come close when I get really hot, but never fully fainted. I'll get to the point where everything goes white and I can't see though. The worst was one winter when I was all bundled up in heavy winter gear and I went to a store that was blasting the heat and taking forever to serve me. I literally had to run outside as my vision was going out, unzip everything and fall in to a pile of snow and lay there for a few minutes before I could go back in. I don't do so well with the heat