I just got on here to discuss the same thing!
I just stayed somewhere for 3 nights, and all my clothes smell like smoke. I could tell the moment I walked in the place that would be the case. It was a holiday weekend and the town was bursting at the seams, so cancelling wasn't an option. While I was there the host only smoked in his room, with the door closed, but it was clear that the whole apartment is usually a smoking place.
I do wish there were somewhere hosts could say if it is a smoking household. I know we can *assume* if it's not listed as non-smoking then it is a smoking house. But come on - there are so many other filters out there.