I've stayed in hotels where I check into a non-smoking room, everything is okay for a few days to a few weeks, and then all of a sudden one day I come back to my room to find it filled with cigarette smoke. After some investigation by the hotel, it was found out that sometimes cigarette smoke travels through the vents connecting bathrooms. Most of these vents are not controllable (no switch in the bathroom), they are just vents that are there. I've had this happen to me when I was in a non-smoking room on a non-smoking floor in a non-smoking wing of the hotel. Apparently, vents can be connected all throughout the hotel.

One time, the smell was so bad and constant, it really felt like there was a phatom person sitting in my bathroom puffing away. The hotel staff came in and agreed that the amount/smell of smoke in the room was just about the same as if one were actually smoking in the room. The hotel brought in some air/ozone purifier that made it a bit better, but for a few days it was just bad. Then I guess whoever was chainsmoking in his room checked out and then it was better again in my room. The hotel did offer to switch me out of my room, but I was in an upgraded suite long term, had all my stuff and office equipment everywhere, they did not have another suite available, so I just stayed and suffered for a few days.

I mean, what else was I to do?