X-ray Screener Training – The Need
X-ray screeners have one of the most important jobs in our airports. Each year they detect many thousands of dangerous objects that individuals intentionally or inadvertently attempt to carry through checkpoints. It’s important to bear in mind that although airport x-ray machines may look very sophisticated, they are essentially just IMAGING SYSTEMS, and NOT automated weapons and explosives detectors. The effectiveness of the x-ray screening depends on the performance of the technology of course – but also just as importantly, on the performance of the PERSONNEL operating the equipment.
Although security screeners have the option, in theory, of hand-searching every item of carry-on baggage, this would be totally impractical in a busy airport environment. ICAO Annex 17 – Security, Recommended Practice 2.3 states: “Each Contracting State should whenever possible arrange for the security controls and procedures to cause a minimum of interference with, or delay to the activities of, civil aviation provided the effectiveness of these controls and procedures is not compromised”. In this context, airport authorities need to have security procedures that maintain passenger flow and so responsibility must be placed on screeners to VISUALLY examine the vast majority of hand-carried bags using x-ray, rather than hand-searching.
The human operators manning airport x-ray machines must carry out a wide variety of tasks, including ensuring baggage is placed properly on the feed belt of the x-ray equipment to ensure effective image production, operating the controls, monitoring the x-ray images and making decisions about each baggage item, as well as carrying out risk assessments of passengers to select those requiring enhanced security screening. A single mistake from an x-ray screener at an airport could result in a terrorist attack on an airliner, which could mean the loss of hundreds of lives. Therefore, it’s vital that training of screening personnel is of the highest possible quality as it has a direct correlation on the effectiveness of the security screening performed.
The detection of threat items in baggage using x-ray is not as easy as many people may assume. On the contrary, it’s an extremely challenging task and one of the most demanding roles in the aviation security system. It’s worth remembering that in a hospital a radiologist will examine each medical x-ray image for several minutes and often consult with colleagues before making a diagnosis. Also, a medical x-ray image is viewed in a quiet and darkened room, with no distractions. In many airports, the screeners are expected to work at the speed of the conveyor belt of the x-ray machine, so the screeners have only about 6 seconds to inspect each bag image. Within this very short time period the airport x-ray screener must intensively scan for prohibited articles and make a decision about each luggage item. And x-ray images in airports are viewed in bright light with noise and a multitude of other potential distractions. The sheer number of bags that have to be screened and the cluttered patterns on each bag image makes it very challenging to identify dangerous items, especially as many objects look totally different under x-ray to how they appear in reality. A screener may find it relatively easy to identify large, predictable, high-contrast threats like firearms and metal knives viewed in familiar side profile – but if a weapon is viewed from above, or from its end, it will be far more difficult to identify. And x-ray screeners aren’t just looking for easily identifiable threats like guns and knives. Since the 9/11 attacks, even objects such as containers of liquid, nail scissors, razor blades, cigarette lighters and plastic knives are classified as potential threats by many airports. But airport security operations haven’t generally increased the time available for screeners to find these increasingly harder-to-spot items.
Identifying explosives with x-ray is even more difficult than detecting weapons, because explosives do not have defined, predictable forms. They can be liquid or gas, or solid in any shape or size. Terrorists use Improvised Explosive Devices (IEDs), which don’t generally comprise sticks of dynamite and an alarm clock (stereotypical bombs are virtually nonexistent), but often utilise plastic explosives which can be moulded into an unlimited number of innocuous/ambiguous shapes and objects – including thin sheets which terrorists have used to line bags. Detonators, switches and the other metallic components in IEDs are usually extremely small, delicate structures, easily concealed in a packed bag. The problem of spotting IEDs with x-ray is further complicated by the fact that plastic explosives have densities and characteristics which make them appear similar to many non-threat, organic materials (such as plastic, leather, rubber, paper, textiles and foodstuffs) routinely carried in baggage. If an explosive device is present in a packed bag it will almost certainly be partially obscured by denser innocuous items.
Terrorists are extremely cunning in concealing IEDs, often camouflaging them in electronic items where the complex circuitry makes the bomb components difficult to identify. The Pan Am Flight 103 bombing over Lockerbie, Scotland that claimed the lives of 259 passengers and an additional 11 people on the ground was the result of a small amount of Semtex, an extremely powerful plastic explosive, hidden inside a cassette recorder. Suicide terrorists may even distribute components of an IED over several bags for later assembly during a flight, as they plannned to do in the UK Liquid Explosives Plot of August 2006. The bombs, made from liquid hydrogen peroxide explosive carried in 500ml bottles of soft drinks, combined with batteries, wires and detonators, would have been assembled in flight and then detonated to deadly effect.
Screening equipment needs to be used in conjunction with highly-trained and motivated personnel. It is crucial that the knowledge and skills of airport screeners are continually reinforced, including gaining new skills based on evolving threats and new methods of concealment. Properly trained x-ray screeners may help us avert another major aviation terrorist incident.
