MIL-HDBK-1013/1A
used, high initial purchase, installation, and maintenance costs. The cost-
effectiveness of using exterior detection along extended perimeters to gain
added intruder ingress/egress time must be weighed against the cost of
hardening the building more and installing IDS in a smaller area at or within
the building. Figure 7 shows that the time to penetrate or climb over a
perimeter fence is only a few seconds (about 0.1 minute). Figure 8 also
shows that the ingress time for an intruder carrying up to 35 pounds (16 kg)
of tools covering distances of up to 400 feet (122 m) between the fence and
building is less than a minute. Given the nominal amount of time gained
relative to the expense involved, the use of guards or IDS on extended fence
perimeter is recommended only if required by DoD regulation. Exterior IDS
options are discussed in par. 4.5.