While I can understand your concern--no one wants to live across the hall from a meth lab--just the smell of cat pee would not be enough for me to notify the authorities. It's possible that someone in the building has a cat that they let out into the hallway. (Why they would do that, I have no idea, but it's possible.)

I found this list of warning signs of a meth lab:

â¢Unusual, strong odors (like cat urine, ether, ammonia, acetone, or other chemicals).
â¢Residences with windows blacked out.
â¢Renters who pay their landlords in cash.
â¢Excessive traffic in and out of the residence at un
usual times.
â¢Excessive trash including large amounts of items such as antifreeze containers, lantern fuel cans, stained coffee filters, drain cleaner, and duct tape.
â¢Unusually large amounts of clean glass containers being brought into the house.
â¢Secretive/protective area surrounding the residence
(video cameras, alarm system, guard dogs, reinforced doors, electric fencing).
â¢Persons exiting the residence to smoke.
â¢Little or no mail, furniture, and no newspaper delivery.

I'd say if you saw three or more of those warning signs, I'd call the police and tell them what you suspect. Let the police deal with the matter from there.

Be careful with the smoking outside one, though. A lot of people I know who smoke only smoke outdoors, as they don't want their homes smelling of smoke.

But if you have the cat pee smell and you can't locate a cat, and the guy smokes outsdoors and all his windows are blacked out and there are a lot of late-night visitors, then I think you should call the cops.

And you can always just call the landlord and tell them the hall smells and could they come out and clean it?

I would contact the landlord or super & complain of the odor before I called the cops.