I'm not sure why you haven't called the cops yet. If your worried, and can smell it through the walls? You can try and figure it out all you want, (why does it matter what drug it is) but you could possibly be in danger. Your not the police it's not really your place to try and figure this stuff out.
NOT trying to be a bitch, Just saying, meth dealers don't play. You don't want to get hurt if that is the case.
:ghug2