We all know that canines have a powerful sense of smell, but how far can a dog smell?
Is a dog’s smell as strong as everyone makes it out to be, or is it just all part of the hype?
In the past decade or so, scientists have been working to answer those exact questions.
In this article, we’ll look at some studies that have sought to answer the question “how far can a dog smell?”
We’ll answer questions like “how good is a dog’s sense of smell?” and compare a dog’s sense of smell vs humans.
After reading this article, you’ll have a better idea of what your pooch is smelling.
Dog Sense of Smell
You may have heard about a dog’s reputation to “detect odors in parts per trillion” or “detect a chemical in a solution diluted to one to two parts per trillion.”
While scientists seem to understand what these terms mean, the average person indeed doesn’t. So, before we jump into answering the question “how far can a dog smell,” we need to learn some of the scent lingo.
When someone says that a dog can detect “one part per thousand,” that’s the same as saying a dog can detect one scent that has been diluted by a thousand other particles.
For example, a dog can identify one grain of sugar in a thousand grains of salt or one rotten apple among a thousand fresh apples.
That is really some nose.
Dog Sense of Smell vs Humans
How does a dog’s sense of smell compare to humans, and how does one measure how far can a dog smell versus how far people can smell?
The general consensus is that a dog’s sense of smell is 10,000 to 100,000 times more accurate than a human’s smell.
James Walker, while studying a canine’s ability to detect cancer through smell, likened this to vision: “If you make the analogy to vision, what you and I can see at a third of a mile, a dog could see more than 3,000 miles away and still see as well.”
A dog’s sense of smell is so much greater than a human’s that it is nearly impossible for us to imagine having a sense of smell so powerful.
Just imagine being able to detect things buried feet under the ground or smell precisely how much sugar is in your coffee.
The difference is astronomical.
How Do Dogs Smell So Far?
Clearly, the answer to how good is a dog’s sense of smell is impossibly well.
So, how do they do it?
Firstly, dogs have two air passages—one they use for breathing and one they use for smelling. When the air comes into a dog’s nose, it is separated by a flap. One tunnel goes to the lungs to allow them to breathe and the other enables them to smell.
When a dog breathes, about 12 percent of her air intake is directed into the specially designed smelling chamber. Within this area, the air fills hundreds of tiny tubs. These tubs sieve odor molecules based on their chemical makeup.
This allows dogs to literally break down the air around them and detect even the smallest molecules.
When you compare this to our olfaction system, you can see a huge difference.
Our sense of smell comes from a tiny region in our nasal cavity. This area lies directly in our main airflow path, so all the air that we breathe passes over this area.
When we breathe in, the air moves over this spot and the most substantial scent markers are detected. When we breathe out, the air we smell goes out as well.
Our olfaction system only has a second to recognize scents before we exhale.
The separation of the breathing and smelling function inside a dog’s nose gives them a massive advantage over us.
How Jacobson’s Organ Influences a Dog’s Sense of Smell
Dogs also have another critical trait that puts their smelling far superior to ours, Jacobson’s organ. This smell organ is located at the very bottom of a dog’s nasal passage and allows them to pick up pheromones.
These pheromones of chemicals are unique to each species of animal. They indicate to other creatures of the same species about that individual’s mating readiness, gender and other sex-related facts.
The Jacobson’s organ allows dogs to pick up on these signals. Not only can they smell better than us, but they can pick up on chemicals that we just can’t.
Plus, the brain’s detection of these molecules does not get mixed up with the other scent information. It’s almost like a completely different sense.
Now that we know how they do it, let’s look at how far can a dog smell.
How Far Can a Dog Smell?
All of these biological components play into answering the “how far away can a dog smell?” question.
However, the answer to this question isn’t as straightforward as it might appear.
According to the CIA, how far away a dog can smell a scent depends on wind speed and direction, weather, terrain, the height of the thing carrying the scent, and even the density of objects in between the dog and the thing sending the scent.
For example, a dog is much more likely to pick up on a man standing in the same field as him than a mouse standing yards away in a forest.
All these factors contribute heavily to how far away a dog can smell.
On a windy, bright day, a dog might be able to smell a person standing upwind at 40 feet away. But, during a rainy day, a dog might not be able to smell a mouse from a few yards away.
Training also plays a factor. As dogs get better at picking out one scent, they can do it better and detect it from further away.
This is why a trained hunting dog can follow a trail without issue while a younger dog might have difficulties.
How the dog has been trained and how many scents it has been trained to signal for also affects its accuracy.
While all dogs have the same innate sense of smell, it can take a while for a dog to memorize a scent and become proficient at picking it out.
How Far Can a Dog Smell—Conclusion
As you can see, the question “how far can a dog smell” has a more complicated answer than some might anticipate.
How far a dog can smell relies on a number of different factors and can change from breed to breed.
References and Further Reading:
“Human Scent and Its Detection,” 1993, CIA
Lit, L. and Crawford, C., 2006, “Effects of Training Paradigms on Search Dog Performance,” Applied Animal Behavior Science, Vol. 98, Issues 3–4, pgs. 277-292
Pickel, D., 2004, “Evidence for Canine Olfactory Detection of Melanoma,” Applied Animal Behavior Science
Staymates, M., et al., 2016, “Biomimetic Sniffing Improves the Detection Performance of a 3D Printed Nose of a Dog and a Commercial Trace Vapor Detector,” Scientific Reports
Tyson, P., 2012, “Dog’s Dazzling Sense of Smell,” PBS