Honing the hounds

摘要

WHEN it comes to finding hidden explosives, the self-propelled detection system known as a sniffer dog has no equal. But sniffer dogs have to be trained, and that is a delicate process. In particular, the trace levels of explosive vapour involved are so low (because dogs' noses are so sensitive) that accidental contamination of supposedly residue-free "control" samples is a serious possibility. That confuses the animal and slows down its training. Things would therefore go more smoothly if a trainer could find out instantly whether a sample had indeed been compromised by traces of explosive, so that he could tell whether a dog's reaction to a supposed blank was justified.