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The right machine for the job.

THE IDEAL SECURITY screening procedure involves screening everyone who enters a facility using both a metal detector and an X-ray machine. These two devices effectively determine whether weapons, explosives, or both are being smuggled into a facility. They also serve as a psychological deterrent to those interested in smuggling in weapons.

People are frequently observed entering protected facilities where security screening devices are in place but leaving immediately when they notice the detection equipment.

They usually return to the facility later minus whatever they were originally carrying and pass through security without incident.

Realistically, though, most companies cannot afford the luxury of dual screening. Assuming a company has a need for security screening--and many companies do--it is usually the security manager's responsibility to make a recommendation to management. How can a manager decide which application is best for his or her company?

Walk-through metal detectors cost about $4,500 to $5,500. They are approximately seven feet high and three feet wide and weigh around 100 lbs. Many people confuse metal detectors with magnetometers, but they are not the same. Magnetometers measure magnetic field intensity. Metal detectors are based on electromagnetic technology, meaning a transmitting panel emits a field of electromagnetic pulses to a receiving panel. If nothing metallic passes between the two panels, the control unit registers normal. When a metal item passes through the field of electromagnetic pulses, it causes a break in the field and an alarm sounds.

Most manufacturers use pulse technology. Two companies make metal detectors that transmit a continuous modulated magnetic field where the transmitter and receiver operate in phase with each other. Any introduced metal distorts the eddy currents and causes an alarm. These detectors note smaller amounts of metal and can distinguish between ferrous and nonferrous metals. They are ideally suited for environments such as mineral plants, where expensive minerals are likely to be stolen in small amounts.

Metal detectors are available in several forms and are used in different configurations, depending on the user's needs. Walk-through detectors can be used as semipermanent structures or portable units. They are often installed in door frames of embassies courtrooms, and parole offices. The U.S. Marshals Service uses portable units in courthouse lobbies and courtroom entrances for sensitive criminal trials. The U.S. Secret Service uses portable detectors when the president or vice-president travels. Prisons and some probation departments use portable units.

Serious consideration should be given to the environment when planning where to locate screening devices. Ideally, operating a walk-through metal detector in conjunction with an X-ray system requires a duplex 120-volt receptacle on a dedicated circuit to the control panel to avoid overload and interference from other electronic devices. Activation of the X-ray system, the TV monitor, metal detector, and then additional electronics on the same circuit--such as computers--can cause false alarms.

How reliable are walk-through detectors? Tests conducted by federal agencies, including federally funded laboratories, indicate walk-through detectors, when set at the proper sensitivity and tested daily, are extremely reliable. The equipment is even capable of detecting plastic automatic pistols because the guns are 83 percent metal and only 17 percent plastic. Walk-through metal detectors have sensitivity controls and can be programmed to detect any type or size of weapon.

Another type of metal detector is the handheld, or wand, type. This type of detector is convenient for avoiding long lines when a lot of people are passing through a walk-through detector. While handheld detectors can be used alone, they can be extremely useful when used in conjunction with walk-through detectors. For example, when a person moves through a walk-through detector and the alarm sounds, the person then steps aside and the security officer scans the person's body using a wand, allowing other people to proceed through the security checkpoint. When the object that set off the alarm is discovered and removed, the person is again routed through the walk-through for final clearance. A handheld detectors costs between $15 and $200.

X-ray systems detect weapons, liquids, and explosives and are much more expensive than metal detectors--around $30,000 to $50,000. They use X-ray beams to identify contraband by its darkness, shape, and color. The data is processed through a computer and displayed on a television monitor. The image on the monitor depends on the density and absorption characteristics of the contents of the package. When machines with conveyor belts are used, X-ray inspections can be performed rapidly by trained operators.

Worker safety is often an issue. Federal agencies, airlines, and correctional institutions have been using X-ray systems for years without a reported incident of radiation injury. Machines emit only 0.5mR/h, equivalent to the average television.

The Bureau of Radiological Health certifies X-ray systems manufactured by all major companies. If the manufacturer cannot provide certification for a machine, the company should not purchase the machine.

In determining what size X-ray system to purchase or whether to purchase one at all, a company should consider what materials must be examined. If a business has a lot of mail it wants to inspect or if it wants to inspect people's briefcases and purses, an X-ray machine with a conveyor belt--like those used in airports and federal court buildings--is appropriate. If an organization cannot afford a large system, an alternative is to purchase a small package X-ray system, which is available for a few thousand dollars. Although these systems are too small to examine briefcases and purses, they are useful for checking mail.

When choosing a system, management should remember that metal detectors discern metal objects. Metal detectors do not depend on human interest, motivation, or skills to be effective. Once the controls are set, the operator need only have the person remove the metal article before passing through the detector again. Certain explosive, such as C4 (a plastic explosive), cannot be recognized with a metal detector. Most explosives, however, use some metal, such as wire, dynamite caps, detonators, batteries, or timing devices. According to the FBI Bomb Data Center in Washington, D.C., the most common explosive today is the pipe bomb, which is easily picked up by a metal detector.

X-ray systems identify weapons and explosives. They depend on the training, skill, and motivation of the operator. If the operator does not observe certain shadows, shades, or objects, does not inspect the object further, has not been trained properly, or is not interested or motivated enough to be attentive, the X-ray machine is ineffective. The author has passed through many airports where objects in his attache case required immediate inspection according to training literature but were missed eight out of ten times.

If a company's budget does not permit buying both an X-ray system and a metal detector, metal detectors are the best bet since they can detect most contraband and, if programmed correctly, can be operated by almost anyone without extensive training. If a company receives a lot of mail and wants to examine suspicious packages, it might want to consider buying a small, inexpensive parcel inspection X-ray system in addition to a walk-through metal detector.

Lawrence McMicking, CPP, is a supervisory security specialist for the United States Marshals Service in Arlington, Virginia. He is a member of ASIS.
COPYRIGHT 1993 American Society for Industrial Security
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 1993 Gale, Cengage Learning. All rights reserved.

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Title Annotation:Physical Security
Author:McMicking, Lawrence
Publication:Security Management
Date:Feb 1, 1993
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