Detection is the process of surveillance where the collected data is segregated for individual monitoring of things under surveillance. It helps in detecting the presence of strangers and locating foreign objects in any given area. In detection, the surveillance is taken to the ground level where everyone and everything present in the area under surveillance is individually examined. It is a physical examination done with detection tools. A door frame metal detector is a good example of a detection device. These devices can detect everything from explosives to smoke. Availability of detection technology allows users to select devices according to their needs.