A detection system, comprising: a plurality of sensors (610, 620, 630, 640), comprising: an entry sensor having a field of view oriented to detect an object entering an entry portion of an occupancy volume; an exit sensor having a field of view oriented to detect the object exiting an exit portion of the occupancy volume, wherein the exit portion is different than the entry portion; at least one approach sensor (630, 650) having a field of view (632, 652) oriented to detect the object approaching relative to the entry portion of the occupancy volume, the at least one approach sensor comprising a first approach sensor; and at least one retreat sensor (640, 660) having a field of view (642, 662) oriented to detect the object retreating relative to the exit portion of the occupancy volume, the at least one retreat sensor comprising a first retreat sensor; an absorber box, wherein the first approach sensor and the first retreat sensor are mounted in the absorber box, the absorber box being configured to block unwanted break-beam responses and to fan sensor break-beams across different detection areas; and a processing system coupled to the entry sensor, the exit sensor, the at least one approach sensor, and the at least one retreat sensor; wherein the processing system is configured to determine whether an object of interest has entered the occupancy volume and to output a signal indicative of whether an object is detected within the occupancy volume; wherein if the output signal indicates that an object is detected within the occupancy volume, the system is configured to initiate a scan for unwanted materials. a plurality of sensors (610, 620, 630, 640), comprising: an entry sensor having a field of view oriented to detect an object entering an entry portion of an occupancy volume; an exit sensor having a field of view oriented to detect the object exiting an exit portion of the occupancy volume, wherein the exit portion is different than the entry portion; at least one approach sensor (630, 650) having a field of view (632, 652) oriented to detect the object approaching relative to the entry portion of the occupancy volume, the at least one approach sensor comprising a first approach sensor; and at least one retreat sensor (640, 660) having a field of view (642, 662) oriented to detect the object retreating relative to the exit portion of the occupancy volume, the at least one retreat sensor comprising a first retreat sensor; an entry sensor having a field of view oriented to detect an object entering an entry portion of an occupancy volume; an exit sensor having a field of view oriented to detect the object exiting an exit portion of the occupancy volume, wherein the exit portion is different than the entry portion; at least one approach sensor (630, 650) having a field of view (632, 652) oriented to detect the object approaching relative to the entry portion of the occupancy volume, the at least one approach sensor comprising a first approach sensor; and at least one retreat sensor (640, 660) having a field of view (642, 662) oriented to detect the object retreating relative to the exit portion of the occupancy volume, the at least one retreat sensor comprising a first retreat sensor; an absorber box, wherein the first approach sensor and the first retreat sensor are mounted in the absorber box, the absorber box being configured to block unwanted break-beam responses and to fan sensor break-beams across different detection areas; and a processing system coupled to the entry sensor, the exit sensor, the at least one approach sensor, and the at least one retreat sensor; wherein the processing system is configured to determine whether an object of interest has entered the occupancy volume and to output a signal indicative of whether an object is detected within the occupancy volume; wherein if the output signal indicates that an object is detected within the occupancy volume, the system is configured to initiate a scan for unwanted materials.