The use of dogs in search and rescue (SAR) is a valuable component in wilderness tracking, natural disasters, mass casualty events, and in locating missing people. Dedicated handlers and well-trained dogs are required for the use of dogs to be effective in search efforts. Search and rescue dogs are typically worked, by a small team on foot, but can be worked from horseback.
Search and rescue dogs detect human scent. Although the exact processes are still researched, it may include skin rafts (scent-carrying skin cells that drop off living humans at a rate of about 40,000 cells per minute), evaporated perspiration, respiratory gases, or decomposition gases released by bacterial action on human skin or tissues.
From their training and experience, search and rescue dogs can be classified broadly as either airscenting dogs or trailing (and tracking) dogs. They also can be classified according to whether they scent discriminate, and under what conditions they can work. Scent discriminating dogs have proven their ability to alert only on the scent of an individual person, after being given a sample of that person’s scent. Non-scent discriminating dogs alert on or follow any scent of a given type, such as any human scent or any cadaver scent. SAR dogs can be trained specifically for rubble searches, for water searches, and for avalanche searches.
Air-scenting dogs primarily use airborne human scent to home in on subjects, whereas trailing dogs rely on scent of the specific subject. Air-scenting dogs typically work off-lead, are usually, though not always, non-scent-discriminating (e.g., locate scent from any human as opposed to a specific person), and cover large areas of terrain. These dogs are trained to follow diffused or wind-borne scent back to its source, then to indicate their find (for example, by sitting with the lost party and barking until the handler arrives, or by returning to the handler and indicating contact with the subject, and then lead the handler back to the subject). Handler technique, terrain, environment (vegetation), and atmospheric conditions (wind speed and direction, temperature, humidity, and sky conditions) determine the area covered by air-scenting dogs, although a typical search area may be 40–160 acres and scent sources can be detected from a distance of 1/4 mile or more. Although other breeds can be trained for air-scenting, the prototypical air-scenting dog is a herding (e.g., German or Belgian Shepherd Dogs, Border Collies) or sporting (e.g., Tollers, Golden, Labradors or Springier Spaniels.) breed that has a reputation for working closely and in coordination with a human handler.
More info at https://en.wikipedia.org/wiki/Search_and_rescue_dog
Juan Gonzalo Angel