What lies beneath
Criticised by privacy advocates, screening technologies that force passengers to 'bare all' have proved an effective way to detect concealed explosives, weapons and liquids.
Over the past seven years, terrorist attacks have been widely publicised by the international media. Following 9/11 and the liquid bomb plot of 2006, it seems the aviation industry is particularly at risk.
In a bid to combat these potential threats, several security companies have developed whole body imaging technologies able to detect hidden weapons and explosives.
These systems, suitable for airport use, are currently being piloted by the Transport Security Administration (TSA). The millimetre wave system and the controversial Backscatter x-ray device have been introduced in several US airports for testing. Lauren Wolf, spokesperson for TSA, says the scanners are proving successful.
"They enable the TSA to detect prohibited items including weapons, explosives and other metallic and non-metallic objects concealed under layers of clothing without physical contact."
UK-based company QinetiQ has developed the SPO-20, a personal scanning system praised for its ability to screen passengers at stand-off distances.
Although it is currently being piloted in ferry and mass transit environments, the technology could soon be employed by airports.
Kevin Murphy, product manager, says: "You're screened in the same manner you might be by a CCTV camera or an infra red camera. It's located in one point or one place but it can screen you, watch you and draw information about you from what it sees and detects."
The system employs millimetre wave technology which detects waves emitted from the human body through their clothing. Security officials are trained to recognise normal wave signatures and flag an alarm if something is radically different.
"What this tells us is that person is different and needs some further investigation," says Murphy.
"We're not claiming we can identify a suicide bomber in the crowd. What we're doing is allowing you to filter thousands of people, down to one or two who pose a potential threat."
This easy-to-use system has a very low training budget, making it popular with the United States government.
"It's easily deployed, it's easy to move around, there are no consumables and there are no particular infrastructure requirements, other than having access to a 13 amp plug, so all of these are additional benefits," says Murphy.
He adds that anyone able to use a computer mouse or joystick could easily familiarise themselves with this technology.
Despite widespread concern about aircraft hijacks, Murphy believes terminal buildings are where the threats lie.
"If I was going to cause mass havoc in an airport and maybe shut the terminal down, I would blow up the security area itself. So you need technologies that actually work against the suicide bomber walking through the terminal and possibly shutting it down for a day or two whilst they deal with the aftermath."
To prevent such a situation, Murphy argues it's important to position detectors further away from terminals, to build up profiles of particular passengers on approach. By identifying potential risks early on, security officials are better able to monitor the situation and act accordingly.
"What you don't do is shoot them, that's not the concept of operations," says Murphy. "What you can do in approaches to a checkpoint is direct people who flag an alarm into a higher security lane, where instead of metal detectors there may be trace detectors or backscatter systems."
For the TSA, a defensive layer system of security measures is critical for ensuring passenger safety. "The use of whole body imaging is a significant step forward in checkpoint technology," says TSA administrator Kip Hawley.
"We are providing our officers with another tool to enhance security and protect the public from evolving threats."
QinetiQ's bosses insist they are not trying to overthrow traditional methods used in airport security.
"Magnetometers are very good at dealing with guns or knives or anything with a reasonably large metal content. The SPO technology just adds an extra layer of security, it does things the magnetometer doesn't - like detect liquids, gels or plastic explosives," says Murphy.
US security company American Science and Engineering (AS&E) has developed a slightly different security system known as the SmartCheck Backscatter device.
The system, which was first piloted by the TSA at Phoenix Airport in 2007, can detect illegal objects very effectively.
"What we're doing is generating a very small ray of x-rays which we refer to as a pencil beam. Using this mechanical scanning technology we basically create an x-ray beam that can move back and forth and up and down to scan an area," says Joe Reiss, vice president of marketing, AS&E.
"We're collecting the scatter off the object we're scanning, in this case a person, so we can look at the signal of the reflected x-rays. We use those scattered x-rays to generate the images. Different types of material will scatter different rays, making it easy for security officials to detect explosives or narcotics."
Though concerns about radiation exposure have been expressed, medical scientists have dismissed the risk as "trivial".
Even for frequent travellers, the effects are so minimal they pose no real health threat. A person would have to be scanned hundreds of thousands of times for the issue to even merit discussion.
As Reiss points out, people are exposed to radiation on a daily basis, and particularly so during air travel.
"When you're flying in an aeroplane you receive the same amount of radiation in two minutes that you do by undergoing one scan by one of these SmartCheck systems," he says.
In addition the technology is very simple to use. Training sessions are very short and analysts quickly become accustomed to recognising objects displayed on the images.
Reiss says: "Security officials are trained to position passengers. The machine itself is very simple, you just press a button to start. A lot of the training is just having people become familiar with looking at and interpreting images."
According to AS&E, officials are often capable of detecting anomalies after only a few hours of training.
Despite the detection success rates of these technologies, the images they produce have caused considerable controversy.
While privacy advocates argue that the anatomical detail present on some of the images is invasive and unnecessary, system developers insist they are doing everything they can to protect passengers.
Reiss argues there are several ways to safeguard privacy: "We feel we've done a lot in terms of how the software displays the image to remove a lot of the detail of the subject's anatomy," he says.
"Also, the security official who's looking at the images is in a remote location, so they're not in visual contact with the person being scanned. The person who sees the image is a different officer to the one who is in contact with the person."
Another common concern is whether any of these images can be stored or transmitted. According to Reiss any problems will be resolved in the terminal, so there's no real reason to save the data.
"The systems are designed so that when they are placed in operation the software that runs the system does not have the capability to save or transmit images."
AS&E's management is confident that privacy issues will not be a problem. During pilot tests in Phoenix some 80% of passengers chose to be scanned by the SmartCheck device, rather than face a more invasive pat-down search.
QinetiQ's millimetre wave technology also produces detailed images. "One of the critical things about these technologies is the avoidance of any privacy problems that would cause upset to either the persons being scanned or cause wider public unquiet," says Murphy.
"We avoid privacy problems in our screening by never presenting the concealed information at any point."
TSA's management agree that protecting the public is a number one priority.
Wolf says: "The system will not store, export, print or transmit images and facial features will be blurred for privacy. All images are deleted from the system after they are reviewed by the remotely located operator. All machines have zero storage capability."
At present, no Middle East airport has adopted any of these systems. Andrew Chupeau, senior media officer, Abu Dhabi Airports Company (ADAC), says that if such a technology was ever employed, management would operate the device with the utmost cultural sensitivity.
In the meantime ADAC continues to offer women the opportunity to be privately searched by a female official in a separate room.