The section of a dog's brain related to processing smells is almost seven times larger than ours. In addition, the dog’s fantastic sense of smell can be explained by the fact that dogs don’t exhale when sniffing a faint scent. This enables the dog to sniff faint odors without disturbing or destroying them.
Dogs have a wing-like flap in each nostril that determines the direction of the airstream in and out of the nose. When the dog inhales, an opening above and beside this flap allows air to pass through. When the dog exhales, this opening closes and the air comes out below and beside this flap through another opening, enabling the dog to increase its collection of odors. As a result, the warm air that is exhaled flows backward and away from the odor being sniffed, preventing them from mixing.