I think a bigger issue is that they only use dogs as means of getting a warrant later. In other words , cops do the searching for drugs. Not dogs. The dogs are merely there to say, yes there are drugs here, you may now get a warrant to search that area or building. He dogs are also used for intimidation. To get confessions. "Tell us where it's hidden, or else we will release the dog" Make it easy for us and you get a deal sort of speech.All the busts I've seen in apartments and houses had no dog. Like you say, the smell is everywhere in a small place. The dog is useless. Cops already know there is drugs there. For cars, they use the dog when the driver says no o a search. They call the dog in and he comes and sniffs around. If he shows signs , then they are allowed to search deeper or get a warrant. The dog is a drug detection tool, and not a searching tool. Getting their precious dog in harms way sniffing Around a drug den with syringes and drugs lying around isn't to likely. It's cruelty really. I wonder how many dogs got poked with dirt syringes and sniffed up drugs while searching junkie places?