They look like friendly service dogs. But these canines are specially trained to pick up vapors from explosives wafting through the air from suicide vests, belts and backpacks. They can pick up the scent of a suicide bomber from several football fields away.

The police now have at least eight vapor-wake dogs, each named after a fallen NYPD officer. They’re as part of a department effort to boost security at concerts and other places where large groups of people gather.