Dogs can be trained to smell anything they want.

http://www.usmc.mil/marinelink/mcn2000.nsf/0/5BE30F4DE7FBACCE85256DC1005A9492?opendocument

I remember many years ago, some advocates of old Abbie Hoffman were suggesting that the general public buy some of the concentrated scent chemicals they use to train dogs with (they arent trained with real pot or real C4, at least not always) so they encouraged everyone to buy the chemical that smelled like pot or cocaine, and spread it in every public mailbox you see as often as you can.

If enough people did it, it would make sniffing the mail worthless, or so was the idea.

Natutally I wouldn't WANT to mess with the mail nowdays - let the dogs do their best smelling ever, and keep our postal people and our public safe.

(Yes I am willing to trade a tiny bit of liberty for a large amount of security, in the same way that I will not allow the 1st Ammendment to give some jerk the right to yell "FIRE" in a crowded theatre).

Sorry got off topic again - I DO know they can smell K's, dunno about O's or H's but I'd assume so.