If it was explosives and a dog got a 93% alert rate irrespective of there being any explosives, then that would be useless and nobody in their right mind would

If it was explosives and a dog got a 93% alert rate irrespective of there being any explosives, then that would be useless and nobody in their right mind would use that dog, as it would have them search 93% of everything. At that point you might as well give up on faffing about with a sniffer dog and just search the remaining 7%.