With up to 300 million scent receptors, dogs are among the best smell detectors in the animal world. The human nose, by comparison, contains only around 6 million scent receptors. Dog brains also devote 40% more brain space than humans to analyzing odors. That’s why people train dogs to search for diverse targets via smell, from illegal drugs and agricultural pests to missing persons, endangered wildlife species and more. Dogs accomplish this by successfully recognizing the odors of substances called volatile organic compounds that are specifically associated with these targets. Not only can trained dogs detect these volatile organic compounds, but oftentimes they can do it with greater sensitivity than analytical instruments. Volatile organic compounds can be produced by living organisms as well as by natural or synthetic materials. In humans, they are produced by the body’s metabolic activity, then enter the bloodstream and are finally released into the air …