[cnn-photo-caption image=http://i.cdn.turner.com/cnn/2009/TRAVEL/12/30/airline.terror.scanners/t1larg.scanner.afp.gi.jpg caption="A staff member demonstrates a full body scan at Manchester Airport in the UK" width=300 height=169]
The Netherlands said Wednesday it was installing the scanners at Amsterdam's Schiphol airport, where security staff failed to detect explosives being taken aboard Northwest Airlines flight 253.
How do these scanners work?
There are two types of device which offer full-body scans. Millimeter wave scanners use extremely high frequency radio waves which are processed by a computer to produce a detailed 3D image of air passengers. Backscatter scanners use high energy rays that - unlike X-rays which penetrate objects - scatter when they hit materials, allowing computers to render a detailed image and detect substances such as explosives and plastic weapons. Both scanners, unlike conventional X-rays, can strip away layers of clothing, accurately mapping the contours of the body, any prosthetics beneath the skin, as well as clothing and metallic and non-metallic objects.
How long does it take?
The scanning process takes between 15 and 30 seconds. Passengers enter a small booth or archway and raise their hands while radio waves target them from all directions. It may take slightly longer for airport staff to review the images produced and - given the level of detail, more passengers may find themselves subjected to follow-up security checks as a result.
Why are they controversial?
Privacy campaigners say the scanners produce "naked" images of passengers which represent an unnecessary violation. They say the process is humiliating, and despite pledges that the images will not be stored or used elsewhere, it could be open to abuse - particularly with scans of celebrities. Although the U.S. Transportation Security Agency, which is installing the scanners in many airports, insist the equipment does not capture details of face or produce images of a quality that can be deemed compromising, opponents say the technology is still capable of this and may be utilized in the future.
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