A dog stops and sniffs the air. His head is held high and his nostrils are flaring. Soon, he starts cantering following an invisible cone of scent which gets him closer and closer to the target.

 Bingo! The dog has found a person hiding behind a big bush. This person is playing the role of a missing person and the dog is rehearsing what he's been precisely trained to do: search for people.

Trained search and rescue dogs are specifically trained to locate the scent of people.

 Interestingly, these dogs can be trained to search people by sniffing the air or sniffing the ground. By getting better accustomed to how a dog's nose works, it is possible to gather a closer insight into why dogs sniff the air. 

A Plethora of Wafting Smells

When dogs sniff the air, they detect small invisible molecules that float in the air (volatile) and end up in their noses. Once in the nose, these molecules reach the olfactory epithelium (a small patch of tissue at the back of the nasal cavity) where they attach to special sensors that send signals to dog's brain through the olfactory nerve.

Once the brain is reached, interpretation of the smell takes place just like data being entered into a computer and being processed. What kind of information does scent provide to dogs?

Smells detected can warn the dog of impending dangers, help him locate mates, find food, or detect animals which may be potential prey or potential predators. 

It is also possible that dogs may be capable of "smelling" the arrival of an impending storm, hence why dogs suffering from brontophobia (phobia of thunder) seem to have the uncanny ability of predicting bad weather.  

Research has revealed that the olfactory acuity of the dog is roughly 10.000 to 100.000 times greater than that of the human. (Walker et al. 2003, 2006), so for sure dogs have a lot of interesting scents molecules to detect by simply sniffing the air.

"There is no such thing as 'fresh air' to a dog. Air is rich: an olfactory tangle that the dog's nose will diligently unknot," says Alexandra Horowitz in her book: "Being a Dog, Following the Dog Into a World of Smell.

Did you know? According to research by G. Settles, dogs detect smells that are far away and inaccessible by doing a long sniff; whereas, when the smell is close by and on the ground, dogs sniff in short bursts. This strategy likely leads to the ideal presentation of molecules to the receptors of the dog's olfactory epithelium.

While humans enjoy the gorgeous scenery, dogs on cars rides enjoy exposing their noses to the wealth of information as the world passes by.

While humans enjoy the gorgeous scenery, dogs on cars rides enjoy exposing their noses to the wealth of information as the world passes by.

Why Do Dogs Sniff the Air Out of Vents/Windows?

It's a classical scene: you pass a car going slow and see a dog with his head sticking out of the window, ears flying and a blissful look on his face. What's up with these dogs?

While humans enjoy the gorgeous scenery, dogs on cars rides enjoy exposing their noses to the wealth of information as the world passes by. They don't even need to lower their heads: the potpourri of scent is sent directly to them. Regular windows in the home can also provide a similar experience. 

A dog instead who acts excited, pacing and sniffing the air coming out of your heating vents should raise your investigative antennae. Many times, dogs who act this way are simply detecting the scent of some small critters, which may possibly be gaining access inside those air vents. 

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Rats and mice are notorious for running on eaves and getting into heating vents which can make dogs go crazy. Whining, nervous pacing, and air sniffing are often witnessed. 

Something to consider: At times, in the case of dogs sniffing the air coming from air conditioning vents, it may happen that some animal happened to urine mark the outside unit causing the smell to drift through the vents.

The Art of "Air Scenting"

A dog's ability to sniff the air and detect chemical compounds has been put to work for a noble cause: helping find people in disaster areas and avalanches. How do dogs accomplish this?

According to Virginia Search and Rescue Dog Association, humans constantly shed countless microscopic particles in the air that carry a distinct human scent.

These particles become airborne, meaning that they are suspended in the air, and are carried by air currents across distances. 

When this scent is concentrated, it indicates that the dog is nearing its source; whereas, as the scent becomes gradually more and more dilute, the dog is distancing himself. 

Air scenting search and rescue dogs are specifically trained to locate any human (whether alive or deceased) in a specific area even up to hundreds of meters away and even under difficult conditions such as in the dark or in dense brush. 

While dogs sniffing the ground, for the purpose of tracking, tend to carry their heads low so to detect the scent of broken vegetation, dogs air scenting will instead carry their heads high considering that they are after the lighter, more volatile compounds left behind by humans. 

Because it can be difficult sniffing all the time while running, considering that dogs need to also breathe, dogs who air scent tend to run a bit slower, going at a canter, explains John Bradshaw, in the wonderful book: "Dog Sense: How the New Science of Dog Behavior Can Make You A Better Friend." 

Did you know? While snow or heavy rain risk destroying important olfactory traces, the movement of air through wind aids a dog’s ability to detect scent, and light rain can help too, bringing back to life scent-emitting particles which may have dried up during the day.

The movement of air through wind aids a dog’s ability to detect scents.

The movement of air through wind aids a dog’s ability to detect scents.

Now That You Know...

As seen, dogs have many good reasons for sniffing the air! The world must sure be intriguing from a dog's point of view. It can be difficult to imagine how it must feel to be bombarded with so much olfactory stimulation on a daily basis. Below are a few tips and ideas for dogs who sniff the air. 

  • If your dog is particularly predisposed to sniffing and searching objects, enroll him in the fun scenting sport of nosework or search and rescue. 
  • If there are possible critters living in your heating vents, you may have to dissemble the ducts and clean out the critters in order to help your dog calm down.
  • If your dog is sniffing the air from your air conditioning vents, you may want to have a professional inspect under the lid of the air conditioner vent or the air conditioner tube for any signs of mice or rats.
  • While sticking their head out of the car is a dog's favorite hobby, it's not the safest things to do. Consider that several dogs gets injured by flying debris

References:

  • Being a Dog, Following the Dog Into a World of Smell, by Alexandra Horowitz
  • Sniffers: Fluid-Dynamic Sampling for Olfactory Trace Detection in Nature and Homeland Security—The 2004 Freeman Scholar Lecture, Gary S. Settles
  • Secrets of the Snout: The Dog’s Incredible Nose, By Frank Rosell
  • Dog Sense: How the New Science of Dog Behavior Can Make You A Better Friend, By John Bradshaw


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