The dog is inserted into each room or area on a long line in an attempt to detect the location of the suspect. The dog is then recalled or downed inside of the room where he stays as SWAT officers search around him. Occasionally, the dog may run off line in hallways or stairways, but rarely out of sight of the handler. Because no trained police dog is ever distraction free and the long line gives the handler direct control. Dogs with strong hunt drive may require direct control to recall when they are indicating the location of a suspect.
Extraction is imperative in situations when the dog is injured or wounded during a search.
Additionally, sudden volatile situations may lead to disorientation and confusion, compromising the safety of the dog and necessitating an immediate extraction. The use of some chemical agents may interfere with a police dog's performance. OC or pepper spray definitely interfere with the dogs olfactory capabilities and cause inflammation and discomfort to dogs similar to what a human would experience. HC or smoke will have a psychological affect on the dog as well as a physiological one. Unless trained in smoke on a regular basis, the K-9 may perceive the smoke as a solid object and stop short of it or attempt to go around it.