The dog days of summer are coming to a close, but there are some very special dogs out there working hard to keep commuters safe.

Approximately 650,000 people go through New York's Penn Station each day, more than the daily passengers for all three major New York City-area airports combined.

In this post 9/11 world, there is a lot happening behind the scenes to keep commuters safe.

Rex, a 9-year-old German Shorthair Pointer, has what may be the most valuable nose inside Penn Station.

Along with his partner, Amtrak Police Officer Steven Angelo, their mission is simple: keep us safe by sniffing for explosives, bombs, and even weapons of mass destruction.

Officer Angelo has raised Rex from a puppy, and they have been working together to protect commuters for eight years.

The training process starts as early as 6 months old as part of a program called "Puppies Behind Bars."

The dogs go through odor recognition training and after three months, graduate to the next level, which is working in the stations and on trains for another eight weeks.

The days are long, both working four 10-hour shifts every week. 

As members of the New York Division of Amtrak Police, they are responsible for security for New York, New Jersey and as far north as New Haven, Connecticut.

After a hard day's work, Rex gets to have all of the fun of a regular dog as part of Officer Angelo's family.

"Rex does live with me, all of our K-9 partners live with us,” says Officer Angelo. “When he comes home he gets to be a dog, he is part of the family. “He gets to hang out with us, he gets to run in the backyard, and do all the other things dogs do."

There are several K-9 officers hard at work on patrol as you walk through New York Penn Station, and Amtrak Police have a strict look, but do not touch policy.

"We have very passive looking dogs, all of our dogs are very friendly because they have to be people friendly dogs, and it’s tough we have a do not pet policy,” says Officer Angelo. “So anyone coming into the station is not allowed to pet our dogs. We let them take pictures with us but they can’t pet the dog or touch the dog"

Officer Angelo lives in Monmouth County. 

He started his career as a patrol officer and then moved into the K-9 Special Ops unit.

He finds his work very rewarding being the first line of defense for explosives for a mass transit system.