A dog's best ally

A dog sense of smell is not only more powerful that ours, it is more discerning. Thus a dog can pick out a target odor in a sea of odors, especially if his concentration is reinforced by periodic exposure to an item of clothing or other object handled or worn by the person he is seeking. Air-scenting dogs work off lead, directed in a search pattern by the handler. They work with their heads up, sniffing the air to catch the scent and follow it to the victim. Air-scenting dogs are valuable for searches in collapsed structures, for locating the bodies of drowning victims, and for other searches in which a person is not tracked from one point to another. Because air-scenting dogs work on scent above the ground and range away from the handler, they can work in areas contaminated by human searchers but allowed to air out for a while. After the contamination has settled, the only body giving off air scent will be the quarry.

Trailing dogs work on lead. They follow the skin-cell trail wherever it leads, even though it is mixed with other scents. Bloodhounds are the best trailing dogs. Their long ears and loose facial skin form folds that scoop and trap scent around their noses. In good conditions, Bloodhounds can follow trails that are weeks old, while other dogs must be on the track within hours. Contamination of the area, i.e., if family members have been beating the bushes for a lost relative, can reduce the effectiveness of a trailing dog, for dogs have trouble discerning between the scent of the quarry and the scent of a family member. Hot weather can cause problems, too, for skin cells decompose quickly in higher temperatures.