This is not that unusual of a problem with a before mentioned solution. A couple on the tour said they rented a house. There was one room which smelled bad of cigarette smoke but only on weekdays, never on the weekends (who knows why). Neither one of them smoked. The husband stayed home one weekday from work, walked into the room and called his wife at her job. "Have you been smoking in that room?" She replied "THAT'S WHAT I'VE BEEN TRYING TO TELL YOU". The next week she went into the room and nicely but firmly informed what ever was in there that they didn't smoke and would "they" kindly refrain from smoking in there. She said it took a week and they haven't smelled it since. Never come from a place of fear or anxiety and you may get the results you're looking for.