In 2010, after spending six years and $19 billion on research to develop better bomb detecting technology, Pentagon officials admitted that dogs' noses were still superior to their most sophisticated technology. Now scientists say the reason for this might lie simply in the way they sniff.

In her book Inside of a Dog, Alexandra Horowitz, an assistant of psychology at Barnard College, offers an analogy to show just how powerful a dog's sense of smell is: while we might be able to tell if a teaspoon of sugar has been added to our coffee, place the same amount in a million gallons of water (roughly the equivalent of two Olympic-sized pools) and a dog would most likely be able to detect it.

This ability to single out and pick up even the faintest of odors is what makes dogs invaluable as bomb detectors. They can detect trace explosives in crowded settings such as airports and public transit areas, as well as odorless chemicals like TNT.

However training pooches to be effective bomb detectors is expensive and time-intensive. While all dogs have a superior sense of smell, not every breed is trainable. Hence the on-going quest to develop an e-nose that can equip bomb detectors with the canal physiology of dogs.

In the latest development in this arena, researchers at the National Institute of Standards and Technology (NIST), the Massachusetts Institute of Technology's Lincoln Laboratory and the US Food and Drug Administration have found that the way a dog sniffs could shed light on how to improve trace detection capabilities.

While we don't differentiate between breathing and smelling, a dog, with its far more complex nasal system, treats them as two separate functions. According to Matt Staymates, a mechanical engineer at NIST, apart from having a complex olfactory system, the key to what makes dogs so good at sniffing out bombs is, well, in its sniff. This is a two part-process and key to this is what happens when it exhales.

Breathing and smelling are treated as two separate functions in a dog's nose. When it inhales, the air is channeled into two different paths and when it exhales, the air exits through the sides of its nose so that the exiting air doesn't interfere with its ability to smell. As counterintuitive as it might sound, when it exhales, the outgoing air jets "entrain—or draw in—vapor-laden air toward the nostrils. During inhalation, the entrained air is pulled into each nostril."

Using a 3D model of a Labrador retriever's (one of the most commonly used breeds in bomb detection) nose to mimic how dogs sniff, and together with the help of schlieren imaging – a technique used for imaging the flow of air around objects – and high-speed video, Staymates and his team were able to confirm the above conjecture.

In their first set of experiments, they found that compared with trace-detection devices that rely on continuous suction, the artificial dog nose was four times better 10 cm (3.9 inches) away from the vapor source and 18 times better at a stand-off distance of 20 cm (7.9 inches).

When they integrated it with a commercially available vapor detector, the switch, which enabled it to sniff like a dog rather than inhale in its standard 10-second intervals, improved its ability to detect odors by a factor of 16 at a stand-off distance of 4 cm (1.6 inches).

This research team is not the first to study how the canine sniffing abilities can be used to develop a better bomb detector. In 1997, the Defense Advanced Research Projects Agency launched the Dog's Nose program for this purpose. One of the technologies to emerge from it was a chemical explosives detector called Fido, which was modelled after the canine nasal physiology.

However while there have been various attempts to develop a canine e-nose over the years, the results, while promising, have not yet resulted in a breakthrough for the industry. Reliability as well as the ability to detect things at a distance remain a challenge and while this latest study confirms yet again the dog's remarkable olfactory prowess, it is "just a piece of the puzzle," as Staymates notes. "There's lots more to be learned and to emulate as we work to improve the sensitivity, accuracy and speed of trace-detection technology."

You can read the results of the team's findings in Scientific Reports. In the meantime, here's a lowdown on the e-nose in action:

Source: NIST

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