Q: How do dogs sniff out drugs and explosives?

A: Police and customs throughout the world use "sniffer" dogs to detect drugs and explosives.
Breeds of dogs that are trained for "sniffing" job include labradors, collies and spaniels and other retriever dogs; most popular, however, are German shepherd dogs
Dogs have a far better sense of smell than a human do because the smell receptors at top of their noses are 100 times longer than in humans.
The training course for a sniffer dog normally lats about 12 weeks. The dog is first taught to recognize a particular drug or explosive.
Its handler(the person who trains the dog) hides a sample of the substance inside something the dog can grip in its mouth- a rolled -up newspaper or a rag- which is known as a training aid.
The dog is commanded to bring the aid back to its handler, and then recieves a reward. The reward could be a food or anything that the dog enjoys doing, like a friendly fight or game.