Trailing Dogs follow a scent trail left along the route where the lost person recently passed. They use the scent that explodes off each person from all over his body, leaving an invisible cloud of scent that hands in the air along the trail.
Area Search Dogs (air scent dogs) work off-leash, ranging widely as they search large areas for airborne human scent, which spreads from the lost person's current location -- carried by wind, temperature, and air pressure.
Urban/Disaster Search Dogs help to find those missing in the aftermath of a tornado, hurricane, earthquake, flood, or terrorist attack, often locating victims trapped in buildings and concealed under rubble.
Human Remains Detection (HRD) Dogs are trained to search for the different scents associated with persons who are deceased. HRD dogs can locate materials that are buried, suspended, or at ground level. Forensic specialist HRD dogs are used to search for small trace scent, like blood, hair, teeth, and fingernail clippings.
Water Recovery Dogs search for drowning victims or the remains of subjects submerged in water. The dogs work from a boat, questing for the scent rising from the surface of the water above or near where the remains are located. Dogs may also alert from the shore, using airborne scent.