2. Learning Objectives
After reading this chapter the reader
should be able to:
1. Differentiate between the
capabilities of screening equipment
currently available.
2. Compare the functions and
abilities of trace detection equipment
to x-ray screening technology.
3. Identify the potential problems
related to mass deployment of
backscatter technology within the
United States.
4. Recite the basic components of x-
ray screening equipment.
5. Specify the criteria for successful
performance of metal detectors.
9. Backscatter X-rays
Much organic material is low-density, and does not
show up well on traditional transmission x-ray
images. Organic matter, specifically explosive
material, contains low atomic number (low Z)
elements such as carbon, oxygen, hydrogen, and
nitrogen. AS&E creates photo-like Z Backscatter
images showing organic materials by directing a
sweeping beam of x-rays at the object under
examination, and then measuring and plotting the
intensity of scattered x-rays as a function of the beam
position. This system has proved to be highly
effective. As applied, the device produces a virtually
“naked” image of passengers by bouncing x-rays off
their skin. The device however does enable staff to
instantly detect any hidden weapons or explosives
13. Computerized Tomography (CT)
The system operates and looks like a medical CAT
scanner. The explosive detection device was adapted
based on the same principles. The system first
produces an x-ray scan similar to the conventional x-
ray scanner. An automated inspection algorithm
determines the locations within the baggage where
the absorption indicates a suspicious area; cross-
section CT slices then need to be made to determine
the density, texture, mass and shape of the object.
Dual-energy CT, a theoretically possible, although
not yet implemented option, would also provide
information on the nature of the explosive.
15. Trace Detection
Trace detection refers to a group of products that can analyze a swipe
or air sample, detecting and identifying minute traces of substances.
Some equipment can access the human convection plume, a natural
airflow phenomenon radiating from the human body, to collect any
threatening particles. The process takes four seconds to collect the
trace particles and another eight seconds to analyze it. A proximity
sensor activates both visual and audio prompters for the passenger to
enter. As the person stands in the center of the archway, gradually
stronger puffs of air come from four surrounding columns positioned to
direct them from the lower to the upper body parts of the body,
accelerating the plume at a faster rate than it would naturally rise. The
systems also perform high-speed baggage inspection to accurately
measure mass, density, atomic number, and other physical
characteristics of objects, providing three independent x-ray images of
each bag.
18. Metal Detectors
Selecting a Metal Detector
Hand Held Body Scanners
Previously, passengers were required to pass through simple metal detectors before boarding a vessel or
aircraft or entering a facility or sterile concourse. However, such efforts have been repeatedly found to be
less than 100% effective. There are still easily recognizable deficiencies in many current metal detectors.
They simply do not trap all forms of dangerous weapons. More often, their greatest weakness is often
cited as the inability to detect metals incapable of being magnetized. The scientific principle upon which
metal detectors work is quite simple. Passive systems detect metal by changes in the earth’s magnetic
field. Active detectors operate by creating an electro magnetic field and alarming when the field is
disturbed by metal objects passing through it. In order to satisfy market demand; many companies have
been through innumerable successive generations of equipment. Those improvements have featured
increased levels of security performance in metal detection capability, discrimination of personal metal
objects, and immunity to outside interference. Overall, managers need to contemplate such issues as
external factors or sensitivity to environmental factors (i.e., environmental magnetic noise); physical
construction or size; ease of operation, (i.e., ease of calibration, self calibration, and required frequency of
calibration) and last but not least cost and appearance. The best hand held detectors are light weight in
construction, have a comfortable grip, and a large scanning surface.
22. 1. Define the components of a standard x-ray machine.
2. Explain the science behind x-rays.
3. Discuss the disadvantages of a metal detector system.
4. Draft a one-page explanation sheet differentiating between the
various types of screening equipment available on the commercial market.
5. Construct a floor plan for screening equipment in a facility of your
choice.
6. Compare the advantages of multi-zone metal detection equipment to
the former standard use machines.
Case Study: Evaluate the environmental factors that might interfere with a metal
detector on the premises where you work. How would you advise the security manager
on the appropriate screening equipment to install? Submit a short essay.
Discussion Questions and Exercises
