It really seems to depend on who is working the dog. A disaster dog IMO should never have anything on. Anything can get caught in rubble and be very dangerous, but amazingly I have seen dogs working debris fields with all sorts of things on. A trailing dog should be in a harness and not on a collar so they're not choking themselves, but again, seen it. Outside of that the lines really start to blurr even more and people really start to be all over the place. I know handlers who use the taking off of the collar as kind of a "time for work" set up. I also know handlers who put on a shabrack (the little vest that says SAR on it) for that same reason. Sorry, that doesn't help much huh?