A black Labrador retriever bounds down rows of passenger seats in the terminal at Charleston International Airport, stopping at carry-on bags to take a sniff before moving on to the next piece of luggage or backpack.

It moves past an airline check-in booth before homing in on an abandoned package between back-to-back rows of seats. The Lab, called Gginley after a 9/11 firefighter killed on duty, points his nose on the package and then sits.

The package contained a detonation cord with gunpowder on it, and it was placed there by Transportation Security Administration officials out of the dog's sight to demonstrate how Gginley and three other dogs, all German shepherds, detect explosive devices at Charleston International, the state's busiest airport.

The dogs are trained to sit when they find an explosive device.

"They are trained to do a non-aggressive response," said Kim Barnett, an explosive detection canine handler with the TSA, who also demonstrated how Brit, a German shepherd, could detect explosives.

The dogs aren't new at Charleston International, and there hasn't been an explosive device found at the airport, said TSA spokesman Mark Howell.

The TSA just wanted to demonstrate how they worked through a training aid hidden in a backpack to make the traveling public aware of them when they see them roaming around the airport with a handler in tow, he said.

The dogs also are used to screen cargo and are put into service at sporting events such as the Cooper River Bridge Run and the Masters golf tournament in Augusta, Howell said.

"The dogs will follow the smell of an explosive device in a backpack as someone walks through a crowd," Howell said. He called it a "vapor wake."

Barnett's dog, Brit, lingered around an area behind an airline counter where the TSA official was carrying the backpack before he placed it between the seats.

The dog knew something had been there before walking over to where the backpack had been placed several feet away, Howell said.

"They have a heightened sense of smell from what we have," Howell said. "They can pick up on things better than we can."

He used a pizza shop as an analogy for the dogs' sense of smell versus that of people.

"When people walk into a pizza shop, they smell pizza," Howell said. "The dogs would smell the pepperoni, the cheese and the dough. They can sniff out different components, just like for an explosive device."

Starting as puppies, the dogs are trained at Lackland Air Force Base in San Antonio. They are trained to detect only explosive devices. U.S. Customs and Border Patrol agents handle drug-sniffing dogs, Howell said.

The dogs also serve as a deterrent, he said, because when people see them out in the community or in the airport terminal, they know they are trained to detect explosives.

The TSA doesn't use the dogs on a set schedule. They are randomly used at different times and in different places to thwart would-be criminals from knowing when they are on duty.

Some of the 800 dogs used by the TSA across the nation are now being trained to help screen passengers for expedited check-ins. The program is being used at larger airports, but Howell said it could one day come to Charleston.

People are not allowed to pet the dogs. Instead, when approached by children and adults who want to touch them, handlers give out pictures of the dogs with information about each one on the back as part of an outreach program.

When they detect an explosive, the dogs are rewarded with toys, said Jason Hollingsworth, a TSA canine handler since 2009 who recently moved to Charleston from Fairbanks, Alaska.

"Everybody loves the dogs, and everybody respects what we do with helping make transportation safe," he said.

Hollingsworth, Barnett and other dog handlers also get to take the dogs home with them, so they interact with their families and any dogs they might have.

Hollingsworth loves his job because he gets to play with the dog all the time. "It's a lot of fun," he said.

Reach Warren L. Wise at 937-5524 or twitter.com/warrenlancewise.