Identifying Threatening Items at an X-ray Post2013-08-28T13:01:41-04:00

by Mark D. Hardison, CPO
February 2001
Reprint Protection Officer News - Spring 2000

When working at an X-ray machine, how do you identify an item that may be prohibited? Some things, such as tapes, printed-circuit boards, computers and similar items; will be relatively easy to identify on the X-ray machine. Examples of these items can be used in training. Pictures of the items as they would be seen on the X-ray monitor can be used to identify similarities between the items under scrutiny, and the photographic examples. ( A book of these photos can be assembled concurrent with a regular training program.) If there is any doubt, the X-ray operator can manually inspect the item, and/or insist on a property removal pass. Some prohibited items will vary from location to location; and may change over time. For example, laptop computers may be closely controlled at one facility; and freely passed at the next one.

There are some items that are always subject to control. In this article, I will consider the recognition of firearms and destructive devices.

To identify an item, you will need to know what the item is. You can think of a firearm, not as a "gun", but as a discrete set of parts. Knowing what these parts are will help you to identify the firearm. An easy way to remember and recognize the parts of a firearm, is the old phrase "lock, stock, and barrel."

The’lock’ is the mechanism that fires the weapon. This is why some are called ‘flintlocks’, and others ‘matchlocks’. They were named after the type of lock that made them fire. A modern firearm will also have a lock. The lock of a modern firearm is the mechanism linking the trigger and the hammer, or striker. On a revolver, the hammer is usually quite prominent. On some smaller semiautomatic pistols, it will not look like a hammer at all. But, on any firearm, there will be some kind of firing mechanism. If actual examples of different types of locks are too difficult to obtain, there are gunsmith’s guides with ‘exploded’ (or isometric) drawings of various weapons.

The ‘stock’ properly refers to the handles or frame (often wood) of a firearm. This provides something to hold onto. In most semiautomatic pistols, the magazine (the device that holds the cartridges) is placed into a wheel inside the grip, where the stock is.

The ‘barrel’ is the tube that the bullets are fired out of. I will also include the chamber as a part of the barrel. The chamber is the place that the cartridge sits when the bullet is fired. If there is no barrel, the ‘gun’ will not fire the bullet at deadly velocity. By way of anecdote; over twenty years ago as a young Military Policeman, I witnessed another MP drop about 30 cartridges for an M-16 rifle into a campfire. (He had tripped.) Several of us were struck by the debris of the exploding cartridges; and the next couple of seconds were very exciting. Fortunately, no one was hit in the eye, and there were no injuries. A barrel is a necessary part of a firearm; however, the barrel can be very short; scarcely longer than the cartridge itself. The simplest example of this is probably removing the barrel of a revolver: the cylinder, containing the barrels, can still fire the cartridge.

By remembering the "lock, stock, and barrel" you will be looking for those thing that make up a firearm. It is worth remembering that some firearms can be quickly and easily taken apart and assembled. This can make them look less like a weapon.

The next threat to look for is destructive devices. Primarily, this would mean explosives and accelerants (fire bombs).

When looking for a destructive device, you can use a method similar to the one used for firearms. The key components of a destructive device are the "firing train". The "firing train" usually includes: battery>switch>blasting cap>explosive charge. Please note that one or more of these may appear to be missing.

Batteries, or cells, are used to provide the energy to power the destructive device. While we are all familiar with the common types ("AA", "AAA", "D", and "C" cells, and 9-volt transistor and 6-volt lantern batteries), there are many specialty batteries and cells that will be difficult to detect. At most locations, the X-ray operator will be able to acquire samples of different batteries for comparison, without too much trouble. You will notice that some of the ‘wafer’ or ‘button’ type batteries are very difficult to detect.

A switch can either be a complex electronic component, or as simple as two intersecting loops of wire. Very thin wire may not show up on the X-ray monitor at all. Often, the etched metal plating of a printed-circuit board will also be invisible to the operator. Just because you cannot see the wire on the X-ray monitor, does not mean that it is not there.

Blasting caps are small, nonferrous metal tubes. Usually, they are about a quarter of an inch in diameter; and about two to four inches long. (About 6mm across, by 5cm to 10cm long.) An electrically-ignited blasting cap will have two wires coming out of one end. These are called "leg wires", and they are thin. The "leg wires" often will not show up on a monitor due to their small size. Other blasting caps use a fuze (this is the correct spelling for this device, no matter what the damn spell-checker says!), which is inserted into the end of the blasting cap. These fuzed blasting caps do not seem to be commonly used for mail-bombs or other clandestine explosive devices. (This observation is based on interviews with bomb squad technicians; and the information released by the Bureau of Alcohol, Tobacco, and Firearms, in publicly available reports.) Most powerful explosives will require a blasting caps to detonate them. Charts and photos used to identify blasting caps can often be obtained from your local bomb squad, military explosives-disposal unit, or even a mining supplies retailer.

The explosive charge itself can be almost any shape or consistency. Explosives can range from simple, homemade formulas, such as ammonium-nitrate and fuel-oil; all the way to complex commercial compounds like Dynamite and C-4. An explosive charge charge can be a liquid, a solid, a slurry, or a powder (such as gunpowder and blasting powder). Most explosives will will have certain characteristics in common, however. Usually, the explosive charge is heavy; weighing as much as an equal volume of wet fertilizer. (Nitrogen is a common chemical link between many commercial fertilizers and commercial explosives. TNT is ‘tri-nitro-tuolene’; and nitroglycerine is the base of other explosives. There are other substances, such as chlorates; but nitrogen is the most common. The similarity, and comparison, is not accidental.) If not well wrapped, you may even smell something similar to fertilizers, or other chemicals. You may notice an oily residue on a suspicious package. If you are examining incoming mail, you may notice that a suspicious package:

  • Is excessively heavy for its size
  • Is specifically addressed to a person, or their office or title
  • Has excessive postage
  • Is excessively wrapped
  • May have exposed wires, or strings sticking out

Some destructive devices will have a flammable liquid as the explosive charge. These items may be disguised as bottles of alcoholic beverages, or other liquids. Again, the same rule would apply; for you to look for the firing train.

The procedures to follow if you find a suspicious item, will be determined by your local leadership team. The operator should ask questions about, and be familiar with, that policy ahead of time. Remember that old saying? "Nobody’s life depends on it." It is not true for this task! If you are suspicious of an item; most experts advise to leave the item alone: don’t move it; don’t touch it; and don’t even think about opening it.

For more information about this subject, contact your local bomb squad or military explosives-disposal unit. Also, the Federal Bureau of Investigation, and the Bureau of Alcohol, Tobacco, and Firearms can provide helpful information on this subject.

The information used to train X-ray operators should not be shared with the general public. While everything that I have written about here is in the public domain, it still should not be shared with those who do not have the "need to know."


Mark Hardison is a Certified Protection Officer. He is Physical Security/Loss Prevention Officer in his Civil Air Patrol squadron. In his ‘civilian’ employment; he is a Console Operator in the Security Department of a major financial services corporation in the Phoenix area.