We've all heard of bomb-sniffing dogs, but thankfully that vast majority of us haven't had to give them much thought. But they're a worthy topic and provide a valuable service. Those sniffers can have 300 million receptors in their snouts to our 6 million, and have a much larger nasal cavity that allows them to understand what each odor means. They have a nostril system that allows them to separate air for breathing and air for smelling. They can process each part of an odor and use that to put together a picture in their heads. That's why they make such great bomb sniffers, they are trained to understand each component of a bomb and if enough components are grouped together, they sit down to indicate their discovery (sitting down avoids the risk of pawing at a particularly tempermental explosive).
And, like all dogs, bomb-sniffing dogs are eager to please. They work for the reward of play or snacks and the companionship they have with their trainers. They want to please us, their noses are excellent, and they're smart enough to put together the clues. On the rise since 9/11 there are now not enough bomb-sniffing dogs to fill demand. They're wanted for public events, airports, and any other place people think there might be a risk. But it's better to be low in demand that 'unleash' (so to speak) dogs that aren't properly trained for the task.
One company is working to help train dogs by creating a mixed odor delivery device that can mimic the mixture of both parts of a bomb: oxidizer and fuel. It's difficult to train bomb-sniffing dogs to train with actual explosives and most current efforts are focused on the oxidizer. The actual mixture (as opposed to the patent pending scent mixer) is considered volatile and is therefore not generally used in training. But with the scent mixing device it should hopefully become much easier to train high-quality bomb-sniffing dogs who work to protect us out of the sheer love of it.