Body Scanner Machines
On Christmas day in 2009, a would-be terrorist managed to clear Nigeria and Amsterdam airport security checks to board a flight to the U.S. with 80 g of PETN (an explosive stronger than TNT) concealed in his underwear. His attempt to set off a bomb on the plane failed, but put pressure on governments to employ more advanced imaging technology to screen passengers for explosives and to revamp the security checks system to accommodate that. The challenge lay in developing high-tech equipment that would not unduly lengthen the time taken for security clearance, as an increase of 45 seconds per passenger can result in flight delays of up five 5 hours (Fiorino, 2010).
Puffer Machine
Reproduced from: www.blogcdn.com
In response to this need, the puffer machine was developed. Installed at 34 airports in U.S., it can determine whether an individual is carrying explosive materials, even in tiny quantities. A quick blast of air is released over the passenger’s clothing to dislodge trace explosive particles. The air is then collected and sent to a detector that can identify eight types of nitrate-based explosives within seconds. If a prohibited substance is detected, security personnel are notified via a visible and/or audible alarm.
Reproduced from: www.debbieschlussel.com
The puffer machine is highly effective, being able to detect the equivalent of 1 mg of aspirin in an Olympic-size swimming pool. However, its maintenance costs are very high and it frequently malfunctioned due to its extreme sensitivity to dirt and humidity. This led the U.S. Transport Security Administration (TSA) to abort its five-year contract, $30-million pilot plan. Having abandoned the puffer machine, the TSA decided to focus its efforts on the millimetre-wave scanner.
Millimeter-wave scanner
Reproduced from: www.tsa.gov
One of the most effective machines for detecting prohibited items, be they metal or non-metal, 488 of these devices have been installed in 78 airports across the U.S. to date. The scanner bounces harmless millimetre-wave radio frequency over the passenger’s body via two rotating antennas, and the radio waves that bounce back from the passenger are processed. A black-and-white 3D image will then appear on the screen, with the passenger’s facial features deliberately blurred to ensure privacy. If suspicious objects are seen on the passenger’s body, the operator, usually located offsite, will notify customs officials who will then carry out further checks.
Though highly effective, millimeter-wave scanners have several limitations. For one, they only scan the body surface and cannot penetrate the skin, which means that they cannot detect drugs or explosives that have been ingested or inserted in a body cavity. While cheaper to maintain compared to the puffer machine, each unit costs about US$170,000 which would add up to several billion dollars if installed in every major airport (Fiorino, 2010).
Cost is not the only barrier. Privacy concerns have been raised, with some members of the European Parliament argue that such scanning violates EU citizens’ human rights (Fiorino, 2010). Although there is arguably no invasion of privacy as long as sensitive body parts are not displayed, passenger use of the system is still voluntary in the EU.