I have been in non-smoking rooms on non-smoking floors that have had cigarette burns on the carpet. Some have had ashtrays and matches.

The worst room I had was in Vegas. I reserved non-smoking, but arrived late, and the only room was a smoking room. I lasted the night, but changed rooms the next day. Of course, after any trip to Vegas, everything smells of smoke when you return. Even if you are a non-smoker.