Most bombings in the United States target locations where no security is in place. No attempt is made to look for the explosive device in advance, and it therefore is not detected before it detonates. However, having the capability to detect explosives is highly desirable in at least three key scenarios, each of which involves unique detection requirements.

The first such situation involves a suspicious package, perhaps one discovered on a doorstep or in a public place and causing concern that it may contain an explosive device. An example is the backpack containing a bomb found during the 1996 Summer Olympics in Centennial Park, Atlanta. In that case, the bomb was discovered prior to detonation but exploded before it could be neutralized. Local law enforcement or explosive ordnance disposal personnel who respond in such cases require a detection system that is easy to transport, easy to operate, and inexpensive. The number of systems that can be used to address the threat posed by a suspicious package is inversely proportional to the cost and logistics burden of the system. An affordable, effective detection system might conceivably be placed in every squad car or provided to every explosive ordnance disposal team.

The second scenario for detection of explosives involves checkpoint screening, as seen in mail rooms, airports, and other public buildings. Everything that flows into an aircraft, for example, now passes through a checkpoint to ensure that it contains no bombs. The requirements for checkpoint screening are high