Trained dogs.

[Humanity]

I've been thinking, how much can one dog learn to sniff? I mean there are hundreds of different psychoactives out there (to include RC's and benzos), if not a thousand

I'm pretty sure police-dogs (or SWAT or whatever, am not particularly knowledgable in the 'what institutions have dogs' area) can't recognize RC's as they're fairly new and teaching them to distinct between different benzodiapines would be irrational as they are in most cases legal.

But even scratching those, there are still a LOT of dirrenet chemical and herbal drugs in the world, is there any common knowledge as to what 'dog authorities' can smell and what they can't?

The obvious ones I think:
Cocaine
Cannabis
Heroin
MDMA (and the like)
Amphetamines

The thread is unorthodox, but don't think it's been discussed before.

Hum.

[ojos_de_brujo]

One can teach a dog to sniff anything one wants him to. Outside of police forces, pest control dogs are taught to sniff fungus or termites. In Australia, border police dogs are trained to sniff fruit, since this in not allowed to be brought into the country.
Swim's guess is dogs are just taught to sniff the most obvious things.
But it is possible to teach a dog to pick up all herbal substances (without making distinction between legal and illegal) or alle chemical substances one carries.
What they actually can do depends per dog and per country.