Aw man, that's SO frustrating! When we lived in the city, the neighbour behind us was a smoker and it drove me MAD because in the spring and summer I would be in my house with the windows open and suddenly get a whiff of cigarette smoke. At least in my case I could close my windows (which still bothered me because I LOVE opening my windows on the few Michigan days that weather allows
). I can't imagine having it come through the ventilation system.
I agree that if you rent, talking to your landlord is the best first course of action.
Praying that you are able to find a resolution. This is not something that I could live with either.