The human sense of smell is so much weaker than a dog’s that most people have a difficult time trying to understand what their dog is doing. The human can’t usually help their dog to find odor. But the human helps get the dog to the area where he can find odor safely, and sets him up for success. So you need to keep your nose, eyes and mind open in order to help your canine partner.
Returning to the original question, sometimes your sense of smell is important to quality assurance. Whenever you open a container where you store your birch odor, you should be able to smell an odor (not necessarily be able to identify it). If you can’t smell any odor, it’s probably not strong enough for training, and should be either refreshed, or disposed of and replaced. If hides smells different than usual, something is probably off and you should start over rather than confusing your dog. Always label everything so you don’t have to guess which odor is present.
Similarly, if you open a room that is supposed to hold only cold containers and you smell Birch, then you probably made a mistake and your boxes are contaminated with Birch odor.
Dog In White
Ultimately, an experienced dog who is trained in nosework is the best authority. Once a hide has been placed by an official or instructor, an experienced dog known as the “dog in white” should test the search to verify all is in order before teams compete.
If the dog in white is not indicating a hide that you made, it is usually best to trust the dog and assume there is a problem with the integrity of your hide. Then you should fix the problem, rather than ignore it and risk confusing other dogs. Similarly, if the dog in white indicates on a box that is supposed to be scent-free, then it’s better to remove the questionable box, than to confuse other dogs. Using your common sense and having extra hides and extra cold boxes available are important to your dog’s success.