Clubs and bars tend to be dark and the patrons inebriated. I have to imagine that those factors would go an awful long way toward nullifying any benefit of this

Clubs and bars tend to be dark and the patrons inebriated. I have to imagine that those factors would go an awful long way toward nullifying any benefit of this stuff. Also, if the technology involved is anything like the color-changing "field test" kits that cops use, false positives will be a problem. An associate of mine was booked for "heroin possession" when an overzealous cop decided to test his aspirin during a traffic stop - he was released the instant he got a hold of a lawyer.