Well bear in mind, to train them in the first place they expose them to the real chemicals. I mean they've got stockpiles of the stuff, after all. So it should be an easy matter to run occasional re-licensing exams on them, if you will :)To be honest man, I don't think there's *any* way to hide drugs from a dog. I know that people talk about "in the real world," blah blah blah... I don't buy it. I do not buy it, and I tell you why: these dogs were first made almost perfect by evolution and hunting. Then we came along, and we fucking made them even better at it with selective breeding for desirable traits (like sniffer doggies, yay!).The human olfactory bulb is about 3/4 of an inch long. We can smell pretty well. A police drug dog? Theirs is literally about 3/4 of their *entire body length*. Just think about that. They can detect one molecule out of billions. Or trillions. Or maybe better for some drugs, I don't know, I haven't looked up the stats.That and I watched the episode of Myth Busters where they tested police canines. I mean for real, I don't think it's possible to trick those dogs for some drugs. Maybe even most drugs, but that much I'm not comfortable saying with any certainty.