Dogs have already earned a place in history as man’s best friend, but some work harder for that distinction than others. While some live lives as pampered purse pets, other canines clock in, just like their people do.

When veteran Shane Cox catches a whiff of diesel fuel, he's sometimes transported to Iraq, where he served two out of four deployments as an infantryman in the U.S. Marine Corps. Before he can be sucked into the vortex of anxiety that accompanies his Post-Traumatic Stress Disorder, his service dog Draven, a movie-worthy pit bull with black-ringed eyes, pulls him out of his head.

Service dogs love, rescue and guide humans
Shane's service dog Draven helps him deal with post-traumatic stress disorder.

“He kisses me, a really hard kiss, three times in the face,” says Cox. It’s not the motion that snaps him out of it, but rather the scent. In humans, the olfactory nerve is located close to the part of the brain that regulates memory, which is why diesel or garbage fumes sometimes catapult Cox into a war-zone panic.

“The smell of his very pungent breath will knock me out of it and say, 'Hey, you’re not in the desert,'” he says. “It’s those little things we’re finding out dogs can do.”

Cox is the co-founder of Warrior Service Dogs, a nonprofit that works to match veterans with service dogs. Certified in Dog Training and Behavior Modification, Cox can train shelter dogs and even veterans’ personal pets. Nearly any breed is trainable, he says, as long as the animal has the right temperament. “It’s the dog that fits the job, not necessarily the dog you want,” he often says.

Service dogs love, rescue and guide humans

For example, he once placed a 12-pound rat terrier with a muscle-bound veteran who was looking for a service dog to fit his own stature. “I left him alone for 20 minutes and came back, and this large man was petting this tiny dog, saying ‘I really like this dog,’” Cox recalls. “What you need and what you want are two different things … He adopted that dog that day.”

Mostly, the traits that build a good guide or therapy dog are not breed-specific. But California’s Canine Companions for Independence, whose graduate dogs are employed in diverse professions such as bomb searching and seizure alert, are mostly retrievers.

Jeanine Konopelski, CCI's director of marketing, said the organization has trained Welsh corgis to be hearing dogs, but Labrador and Golden Retrievers do most of the practical tasks. “Things that we might take for granted, but really allow people to be out in the public or be more independent, so they don’t have to rely on a spouse or a caregiver to do what might seem like a simple thing,” she says.

Retrievers aim to please, she says, and have been bred through the years to take well to certain tasks. The black lab Benjamin, for example, gets items from the refrigerator, helps get the coffee together, and carries laundry for his wheelchair-bound owner.

Service dogs love, rescue and guide humans
US Paralympic Sailing Team companion, Morrow.

CCI graduate Morrow, a yellow lab, spends most of his time traveling with Betsy Alison, a coach for the US Paralympic Sailing Team. Morrow, the first dog to be placed with an athletic team has, for the past seven years, helped pull wheelchairs up the dock, helped sailors dock the boats, and carried lifejackets and dry bags. Morrow acts as an emotional support system, too. While the sailors are traveling, many things are out of reach, including their families.

“The dog becomes somewhat of a companion, helping them to feel more safe and supported when they’re in environments different than at home,” explains Konopelski. “Most people using a wheelchair, their home will be set up for them to use.”

A frequent traveler — on the road 150 days a year — Morrow is “proud” to be working, says Alison. “When he has a job and a mission, he’s happiest. He’s always enjoyed what his environment and job has been.

Morrow is naturally sensitive, gravitating toward the sailors who aren't feeling well, either physically or emotionally. “He’ll walk into a room and check with every person with a disability,” Alison says. “He always knows who his people are; it’s not something that I’ve taught him, just what he does.”

It’s the sensitivity that makes Morrow and other service dogs so extraordinary, and what makes them so effective in the debilitating cases of PTSD often found in veterans like Cox.

Service dogs love, rescue and guide humans
Service dogs can ground their owners with comforting kisses.

“Many have high anxiety levels and frequent flashbacks and night terrors every night, reliving the trauma,” says Carol Borden of Guardian Angels, a nonprofit providing service dogs to people with mental and physical disabilities. “Most are sleep-deprived because they’re afraid to sleep or can’t.”

Such a sleep-deprived state creates more anxiety during the day, and veterans can become isolated and estranged from their family and friends, one reason why 32-39 PTSD-afflicted veterans attempt suicide daily. According to Borden, 22 of those attempts result in death. Veterans also have the highest rate of divorce, and a high rate of chemical dependency from self-medication, she says.

But dogs can learn to discern whether their owners are having good dreams or nightmares, waking them before they ever slip into the darkness of night terrors.

Service dogs love, rescue and guide humans

“The dog is able to intervene and do what we call ‘grounding,’” says Borden, which means the dog interrupts the harmful thought process, like when Draven brings Cox back to earth with kisses.

Those interruptions of thought patterns often are the difference between life and death. “Soldiers have described that they have the same relationship with these dogs as with their buddy in the foxhole,” says Borden. “There is no stronger relationship than having someone’s back to survive."

None of the veterans she's paired with a dog has become a statistic, "and we are so proud of that,” Borden says. “I will get someone who’s totally given up. They call and say 'You are my last hope if you can not help me, I’m done.' Every time, thankfully, we’ve been able to talk them into coming and seeing us, and it’s worked every time.”