How Far Away Can a Dog Detect Scent?

It's no secret that dogs possess powerful sniffers. In the same way humans perceive the world via vision, dogs experience the world primarily through smell. Capable of catching scents at long distances, dogs have been put to work rescuing people trapped under rubble, sniffing out drugs and explosives, as well as other tasks where their amazing sense of smell comes in handy.

Beagle dog on a walk in the spring at sunset
credit: androsov58/iStock/GettyImages


Dogs can detect tiny amounts of smell diluted in air, water or far beneath the ground. According to the Marbach Road Animal Hospital, dogs can pick up scents that are diluted to 1 or 2 parts per trillion; This allows them to smell things buried as far as 40 feet underground! In one experiment, a dog was capable of sniffing out whale poop floating in Puget Sound from a mile away, according to Nova. The Whole Dog Journal states that dogs have picked up the scent of people who'd drowned in over 80 feet of water. Their ability to pick up on tiny traces of a particular scent is what allows them to follow trails that are a week old and, some have even been able to detect cancer cells within humans. Now, let's take a closer look at what makes dogs' snouts so spectacular.

Specialized Breathing

While breathing and smelling are essentially the same action for humans, a dog's nose is built to take care of both tasks separately. Dogs have a fold of tissue inside their noses that separates air for inhaling and air for smelling. When a dog breathes, a portion of the air is directed toward a bony network called turbinates dedicated to olfaction, while the rest of the air is diverted to the lungs. Dogs will take deeper, longer breaths for breathing, and use a short sniffing action when smelling something. When a dog exhales, air is pushed out of slits in the sides of the nose, creating an airflow that draws new smells into the noses.

Jacobson's Organ

Dogs have an organ that humans don't possess: the Jacobson's organ. It's located at the bottom of the dog's nasal passage that allows dogs to pick up on pheromones -- important chemical cues all animals produce that signal messages to one another, like mating readiness. The Jacobson's organ is also important for dogs recognizing the scent of other dogs in their pack or puppies locating a nipple to nurse. If a dog is trying to get more scent to his Jacobson's organ, he may pull back his upper lip and rear back his head -- called the "flehmen" reaction.

Compared to Humans

Needless to say, a human's sense of smell pales in comparison to a dogs. Depending on the breed, a dog's sense of smell is 10,000 to 100,000 times better than a human's. While we possess only about 6 million smell receptors, our canine friends can have up to 300 million. The Marbach Road Animal Hospital says that the part of the brain dedicated to processing smells in 40 percent larger in a dog than in a human brain.