Scent Cone or Plume - Scent hugs the ground and gradually spreads out downwind in a cone shape from the subject.
As people walk and move around, they are constantly shedding skin cells. Heavier cells fall to the ground where trailing and tracking dogs can follow them. Lighter cells are dispersed into the air, where light breezes carry them away to where they eventually fall to the ground. Scent gradually spreads out in a cone shape from the subject. Steady breezes carry scent longer distances, especially in flat, open country. Gentle breezes produce a wider scent cone. The stronger the wind, the narrower the scent cone will be. Stronger winds and gusts carry skin rafts farther and disperse them higher in the atmosphere, making it harder to find the subject.
Air Scent Dogs (or Area Search dogs) are trained to find any human scent in large areas such as parks, woods, pastures, and so on. Most air scent dogs are non-scent specific, meaning when they find anyone in the search area, they will alert the handler. Some dogs will stay with the subject and bark. Most dogs do a recall/refind where the dog will find someone, return to the handler, indicate they found someone and then lead the handler back to the subject.
The handler and dog will usually grid search areas, meaning they will cover the search area in a systematic manner until the dog sniffs the subjects scent cone. Dogs will work the scent cone in a zig-zag fashion working into stronger scent until they find the subject. Since air scent dogs see with their noses, their success rate is much greater than that of people walking in a line looking for the subject.
On days with a steady breeze, a trained air scent dog should be able to pick up and move in on airborne scent from 200 or 300 feet away from source. With light breezes or still winds, you should still be able to work your area in a loose grid (wider sweeps). Your dog should be able to move in from 100 feet or more from source. Shifting winds make searching difficult because you may start your dog downwind and, later, the wind direction shifts. In these cases, the best idea is to remain with your original search plan or pattern. The wind may continue to shift and, trying to keep up with it, may leave you wandering around your assigned search area.
Areas with light brush may have a combination of open areas and wooded areas. Vegetation is not thick enough to block or change how scent moves. Dogs should be able to work light brush areas about the same as open fields. With a nice breeze, you will be able to work the area in a loose grid (wider sweeps).Areas with heavy brush can be found in thick woods or un-mowed fields. Tall grasses are harder for dogs to work, as there is little air flow slightly above the ground (where the dog's nose is located). On hot, still days, in heavy vegetation, the scent stays close to the source. It will be necessary to work the area in a tighter grid (closer sweeps).
Forests can vary from open woods, where dead-fall and dense underbrush has been cleared, to thick woods, where no clearing has taken place and dense underbrush has grown up under the trees. Open woods are basically worked the same way as light brush. With a nice breeze, you will be able to work the area in a loose grid (wider sweeps).Thick woods are worked the same way as heavy brush, work the area in a tighter grid (closer sweeps). Working thick woods at night should be done carefully to avoid unseen hazards.
A river, creek or drainage search during the day should be conducted along ridge lines or hilltops on the downwind side whenever possible. This will cover the waterway and the slopes as well. Since cool air falls, an evening search should be conducted in the waterway itself. Waterways can also act as a funnel, where scent flows downwind. If your dog is alerting or showing interest with his nose in the air and unable to locate source, work your dog upwind to where the source may be located.