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Walk-Through Metal Detectors for Personnel
(Chapter 3   Metal Detection, Continued)

Acceptance testing and performance testing

Acceptance testing is a series of rigorous trials designed to determine if a walk-through metal detector is accomplishing what is expected of it. This series of tests is performed after installation and must be repeated after any relocation of the equipment or change to the surrounding environment. The vendor of each particular type of portal will have a series of tests to be performed after setup. Vendor tests are designed to aid in determining the ideal sensitivity settings of the equipment for a particular location and the contraband items of greatest concern. Each school should also have a series of rigorous tests that it will run before accepting or paying for any piece of equipment. The same set of tests can be used by the school later if there is any change to the equipment's environment, especially if the school cannot afford to bring the vendor back in to support them later.

A series of acceptance tests can be devised with knowledge of the weapons that are likely to be present in any particular community. (This threat varies widely in different parts of the country and can change over the years. As no facility can protect itself from every possible weapon in existence, the local law enforcement agency or the school's security department can help determine the most likely threats for that area.)

  1. Determine the three or four most likely weapons for a particular school.
  2. Obtain replicas or equivalent-composition and similarly shaped items for each of these weapons from the vendor, local law enforcement agency, or school security department.
  3. Place these items one at a time on the body of a tester who will walk through the portal with the item placed in various hard-to-detect locations. Conduct about 20 walk tests per location per item. Good locations to test include: the hand, and stuck up into the sleeve, stuck into a sock on the exterior of the leg, stuck into the inside front of the belt, and hidden inside a baseball cap. (Note that this amounts to 20 different trials for each of four different weapons for each of four different body locations—a total of 320 trials.)
  4. Determine the three or four most likely borderline items that are acceptable items to bring into the school but that may cause an alarm.
  5. Place these items one at a time on the body of a tester who will walk through the portal with the item placed in typical locations—i.e., glasses on face, pocket change in pocket, necklace around the neck. The tester should walk through 20 times with each item.

A particular portal may be said to be accepted when at least 19 of each of the 20 walk-through tests for each weapon results in an alarm, and at least 19 of each of the 20 walk-through tests for each acceptable item does not result in an alarm.

In contrast, a performance test is a much shorter and simpler set of trials that should be conducted by the operators of the system at the beginning of each morning before the equipment goes into operation. This test may consist of walking through the portal four or five times with a piece of metal on different locations of the body. If the portal goes off on each walk-through, then the system is said to be performing well and is ready for operation. If the system fails these tests, and no obvious reason for these failures is evident, such as the recent relocation of a metal object next to the portal, the vendor should be called, and the device should be taken out of operation until serviced.

 



Research Report:   The Appropriate and Effective Use of Security Technologies in U.S. Schools