Cancer detection dog training. Springer spaniel being trained to detect cancer. At this training centre, the dogs are trained to detect volatile compounds associated with cancer cells, by sniffing urine and other samples placed on a carousel. The dog reacts to a positive sample by sitting down (no cancer was detected in this test). Dog noses are highly sensitive and are able to detect molecules in parts per trillion. They are potentially more reliable at detecting positive results compared to conventional blood or urine tests. All the dogs live as family pets but visit the centre for training several times a week. Photographed at UK-based charity Medical Detection Dogs. In 2015 the dogs are being trialled by the UK's National Health Service.