Area search or “air scent” usually refers to search dogs that use air scenting techniques to search areas. Air scent dogs work with their nose in the air, will ignore ground scent and will follow and locate people by catching the "hot" scent of people on the wind. Air scenting techniques are very effective for covering large areas quickly and can produce high probabilities of detection if conditions are good for air scenting. They don't need a "last seen" starting point, an article to work from or a scent trail, and time is not an issue. Some air scenting dogs are also trained to scent discriminate, meaning they can be pre-scented on an article from the missing persons and can pick this person from others in the search area. Air scent dogs usually work off lead. Most are trained to find the victim, alert the handler when the victim has been found, and the return the handler to the victim. This is called a re-find.