A similar method of training bees to associate an odour with a reward has also been developed by British company Inscentinel Ltd. “Bees are at least as good as sniffer dogs but are cheaper and faster to train, and available in much larger numbers. It is dependent on the specific odour, but bees can detect some odours that are present in parts per trillion - that’s equivalent to detecting a grain of salt in an Olympic-sized swimming pool,” said Dr Rebecca Nesbit, a research scientist at Inscentinel.