As a host and a smoker myself, I did the following with my listing- I simply didn't tick whether smoking was allowed or not. I live in the tropics, in the countryside, all the doors and windows are open most of the time. I only smoke outside and non-smoking friends have assured me that there is no smoke smell at all inside the house, even the areas where I hang out.
Soon after a guest arrives, when I am acquainting them with where everything is in the kitchen, or we're sitting and chatting, I'll say "I'm one of those dreaded smokers- I'll step out on the road to smoke while you're here, though". This gives them the opportunity to say "Oh, it really doesn't bother me at all", which amazingly enough, almost all have said even though they aren't smokers. If they say "Thank you", or "OK", I restrict my smoking to a far corner of my yard or out on the road. And I never leave dirty ashtrays around.
So far, after hosting for a year I haven't had any smoking guests. But I felt if I said I allowed smoking, even outside, non-smokers would (reasonably enough) assume the room might smell like one of those old Motel 6 smoking-allowed rooms.
I figured if I just didn't list that issue at all in my house rules, then smokers could inquire whether it was allowed or not, and non-smokers could assume it wasn't allowed or ask.