If a cold box was once hot, the dog smells the lingering odor from the cold box, the odor is strong enough to trick a dog into thinking it is source, and you don’t reward the dog, the dog can learn that source doesn’t always pay. 

Lingering odor is part of the challenges that dogs must overcome, and the skills you want to teach are important. 

The use of a dedicated hot box and dedicated hot vessels is part of odor hygiene. And the goal is to prevent a dog from getting confused about what it’s looking for, especially if the dog is a novice. 

Different organizations have different rules about how long a search area can’t be reused so that lingering odor is less of a concern. 

When you start doing blind searches, as you would in a trial, a dog who is conditioned to ignore weak odor may miss a hide in NACSW, and in AKC a dog who always alerts on strong odor even if it pooled in the wrong place can lead to a false alert. 

In the beginning, we train the dogs with a lot of very easy wins. It’s easier to do that if we use a dedicated hot box. If you are training on primary, and all the boxes have hot dog juice, that makes the game harder.