I have what was once an upstairs apartment that is on a seperate heating system With 4 guys upstairs smoking on Mondays we open a window with a fan blowing out and turn on 2 fans and a Hepa air purifier as well. Since the use of the purifier began neither I nor my wife have been able to detect smoke smell in the main house however before the purifier we could smell it at the bottom of the stairs and a little in the hallway going to the stairs, not terrible though.