In most of the houses we've lived in we've smelled cigarette smoke sometimes and neither of us ever smoked. We jokingly say it's the MIL visiting because she was addicted and couldn't stop even when she was dying and on oxygen. She would turn it off and smoke in the hospital room. I don't really believe in ghosts, I've had no experience with anything like that. I guess I'd have to reevaluate if I encountered something I couldn't explain. I do know there are evil spirits and Angels around, I hope I see the Angels!