Hmmm? I don't know the answer here. Could it be paranoia? Gosh, what a terrible predicament.
Is this the first time he has experienced this kind of thing? Maybe he really did smell something. I know my husband has a very keen sense of smell, whereas, I don't.
I don't know what to suggest as you can't just up and move because the neighbors are not nice. This is what I hated about living in apartments. Too many bad influences; however, this doesn't mean you have to associate with them either. Not that you did, just saying.
Wish there was something I could suggest, but don't know other than counseling.
Hope in time he'll be able to move on.
Hugs, Devastated