PHILADELPHIA (WPVI) -- It's the start of Thanksgiving week, and that means some of the highest traffic days at airports across the country. And between the extra crowds and the recent concerns over terror attacks, that also means tightened security for anyone heading home for the holidays.The TSA has implemented the use of canines to help insure the safety of travelers this season.The dogs are a new sight at Philadelphia International Airport. But officials say the roll out of the canines is coincidental that it should come at this time. The TSA has been phasing in the program at airports across the country for several years.TSA agent Alex Broughton explains, "We're another layer that's put in there by TSA to try to keep the bad guys out."Broughton is the handler for Kina, a German Short Hair Pointer. If you should meet them in your travels through security at the airport - smile, but don't pet."The dogs are working dogs, so they're always looking," Broughton said. "They may come around, sniff around your feet, around your ankles, but they won't be too intrusive. And we just ask you to keep on doing what you're doing. Just go through the line like you normally do. Don't stop and try and play with the dog."Kina has a job, trained to sniff and respond to telltale chemical vapors associated with explosives that might trail after a bad guy. Her nose is far more discerning than a human's.TSA spokesperson Mike McCarthy uses the analogy of a pizza shop to compare the human sense of smell with that of these trained canines.McCarthy says, "Where if you walk in you would smell a pizza, these canines could walk into a pizza shop and they would pick up on the flour, on the tomato, on the basil, and on the mozzarella. So it's a much more refined and sophisticated nose on these dogs."Until now, sniffer dogs were behind the scenes with checked baggage and cargo. But Kina is a passenger screening canine - a PSC.Agent Broughton says PSCs are an extra layer of security, and now five of the teams have been assigned to Philadelphia International Airport.