How Bomb-sniffing Dogs Work

Dogs smell bombs like they smell everything else. First, Brandy sniffed. Her sniff reshaped her nose so that air, including odors from the bomb, hit her odor receptors. The signal traveled from her nose to her somatosensory cortex, an area of the canine (and human) brain that processes sensations, including smells.

Brandy then interpreted the smell; she decided she'd smelled an explosive. She did that by the bomb's odor signature, says Lawrence Myers, an associate professor of anatomy, physiology and pharmacology at Auburn University's College of Veterinary Medicine. C-4's signature includes which odors are in it, their ratios and, possibly, whether C-4 tickled a nerve in her nose called the trigeminal. Because Brandy smelled C-4 many times, she remembered its signature, and she knew to sit when she smelled it.

Could another animal have smelled the bomb better than Brandy -- a raccoon, a rat or … you? We don't know which animal has the best sense of smell because no good studies have directly compared animals, says professor Myers.

Although humans smell using most of the same equipment as dogs, differences exist. Dogs are better than us at sucking in odors. Their noses are longer and roomier than ours, so they can inhale more air per sniff. Dogs also have more odor receptors in their noses than we do -- 20 to 40 times more, according to Myers. Despite these two advantages for dogs, whose nose is more sensitive -- meaning, who can smell an odor with fewer molecules of it in the air -- depends on the chemical being smelled. For example, dogs can detect eugenol, an oil in cloves, at one-millionth the concentration that humans can [source: Myers]. However, Myers, in informal experiments, found that humans can smell acetone at lesser concentrations than dogs can.

While dogs largely interpret the world through smell, and we do not, it's not a true advantage for dogs. With training, we can pay attention and discriminate smells as well as dogs can -- wine tasters and perfumers are evidence of that.

All of this leads to an answer scientists often give: "Dogs almost certainly are better than humans at smelling for explosives, but as a scientist, I can't state that," says Myers.

In some indisputable ways, dogs are better. Dogs can sniff closer to explosives on the ground. We'd look suspicious on all fours. Practically speaking, it comes down to whose face we want to put closer to the bomb.

As part of U.S. security, bomb-sniffing dogs work anywhere there might be an explosive. That includes:

Militaries often use bomb-sniffing dogs in war. Every branch of the U.S. military employs them. The dogs help find an enemy through its artillery and make sure an area is safe for troops to pass. As of 2011, bomb-sniffing dogs are serving in Iraq and Afghanistan, says Gerry Proctor, a spokesperson for training missions at Lackland Air Force Base.

U.S. Customs and Border Protection (CBP) also depends on bomb-sniffing dogs. They monitor for weapons and explosives that could be entering the United States. CBP's animals sniff cargo warehouses at ports, as well as passengers and luggage arriving by ship. You'll also find them at land border-crossings, nosing around incoming cars [source: USCBP].

If you've felt something sniff your hand luggage at a U.S. airport, you've probably met a dog working for the Transportation Security Administration (TSA). The TSA's job is to make public travel safe. As you can imagine, many TSA dogs work at airports. They sniff passengers and hand luggage at security checkpoints. If someone reports a suspicious package or incident on a plane, bomb dogs sniff the aircraft, its passengers and its cargo hatch. You'll also see TSA dogs monitoring the aisles of ferries, trains and city subways.

Local police also use bomb-sniffing dogs. They patrol at crowded public events, like the Olympics, and they check schools and workplaces when there are bomb scares.

So far, we've talked about dogs that work for the public. Private agencies also train bomb-sniffing dogs and rent them out. In fact, after Sept. 11, 2001, many entities, including corporations, cruise ships, and individuals hired the dogs as a security cushion [source: Ramirez].

You can think of bomb-sniffing as a one-way game of fetch. On the next page, find out if training is really as easy as throwing a stick.

You won't encounter one central school where dogs learn to sniff for bombs, but you will find both military and Transportation Security Administration (TSA) dogs learning to sniff at the huge Lackland Air Force Base in Texas. Dogs usually start training when they are between 1 and 3 years old. In this window, dogs are the most playful and willing to learn, which is essential for them to learn to work [source: Soule].

A puppy's life before training varies. Customs and Border Protection, for example, adopts its 1-to-3-year-olds from shelters and families, while also buying from breeders and breeding its own [source: USCBP]. The military buys from breeders, too, but first screens the dogs almost like human recruits -- with X-rays and exams, and by taking only dogs that are mild, like to search and won't run at the sound of gunshots [source: Air Force].

Dogs learn the basics of sniffing for bombs in between two and four months. They'll undergo testing and retraining throughout their entire careers though to make sure their skills stay sharp. Each agency has its own training program and style. For example, at the TSA's training facility, you'd spot pieces of airport terminals, airplanes, train and subway cars, plus a parking lot filled with cars. The dogs learn a sequence -- sniff the area, find the bomb, sit and get a toy for good behavior -- and must perform it in all of the mock surroundings [source: Soule].

Sounds easy, until you remember that the canine recruits know nothing at the beginning of training. Trainers must coax out each move. The military first teaches dogs to be interested in the smell of explosives. A trainer will hold the smell of an explosive near the dog's nose. If the dog sniffs it, it gets a reward. That's repeated many times. Next, the trainee learns to seek the smells. If an explosive is hidden, and the dog follows the scent, it's rewarded again. This pattern continues until the "sit, stay and pay" routine is built, says Proctor, a spokesperson for the Military Working Dog School.

A fully trained military dog does its routine as if it were natural: It runs ahead of troops, sniffing and upon smelling a bomb, it sits. The troops stop advancing. The dog runs back to troops to get its treat, and an explosive ordnance disposal team disarms the bomb.

Human handlers train alongside their dogs, learning to watch and lead their canines. The cost of training far exceeds a college tuition, although it covers a lot. TSA pays $218,000 in startup costs per dog during training, then $158,000 per year after that, says Greg Soule, a TSA spokesperson. The money covers the salary of the handler, training, certification, veterinary services, kenneling and dog food.

Do you think your dog could pass training? Find out next.

The TSA and many other agencies mostly use these breeds for bomb-sniffing, according to Greg Soule with the Transportation Security Administration (TSA): German shepherd; a Belgian shepherd called a Malinois; Vizsla, also known as a Hungarian pointer; and Labrador retriever.

These four breeds represent more than just good noses. The TSA prizes them because they smell well; they're calm in crowds and around strangers, and they like to play, says Soule. Playing is important because dogs understand their work as play; it's a daily game of find-the-explosive.

None of these qualities is dispensable, explains Soule. TSA will turn down the finest smeller if it is aggressive because the public won't tolerate a frightening or dangerous dog.

We've made it to the workday. Clearly, dogs don't work like we do, in an eight-hour slog punctuated with some coffee breaks. Dogs lose concentration more quickly. Instead, the TSA limits dogs to shorter shifts and relies on handlers to recognize when their dog needs a break, says Soule. Because the canine workers may not find explosives every day (thankfully), they practice finding hidden explosives daily on the job, so they don't forget the important smells, say both Soule and Proctor.

If you've ever watched a bomb dog in the airport, you may have noticed that it works in silence, with neither a word nor a woof exchanged between dog and handler. So how does either know what's going on? Thanks to those mock terminals and planes at the TSA training facility, being in the airport is enough to tell the dog it's time to search for explosives. Beyond that, much communication happens through the leash. When the dog finds a scent, it leads the handler toward the source. The universal sit signal tells the handler about a find.

At the end of the day, TSA dogs go home with their handlers to sleep. The handler cares for the dog 24 hours a day. These two spend more time together than with almost anyone else. Military dogs go home to kennels.

If the dog gets very sick or ages out of its drive to play, it's time to retire. Retirement age varies, but military dogs retire at age 8 or 9 [source: Air Force].

We hope you've sent a virtual hug to the dogs that risk paw and tail to protect you, all for a toy or treat. Nose around the links on the next page to gain more love for dogs.