Air passengers may once more be allowed to pack beverages, lotions, and hair spray in their carry-on luggage, if imaging technologies to detect liquid explosives can prove their worth. Several competing systems, including multi-energy x-ray systems and a low-field magnetic resonance imaging (MRI) scanner, are undergoing field tests at some airports worldwide.

The evaluations are part of a move by some governments to relax restrictions on the transport of liquids, gels, and aerosols through security checkpoints; they also figure in the overhaul of airport security technologies for detecting trace and bulk explosives (see accompanying story). Since the foiled plot four years ago to bomb several transatlantic flights with hydrogen peroxide–based explosives, security regulations have restricted passengers in the US and more than 60 other countries to transparent 100-ml containers that can fit into a small plastic bag.

A new x-ray scanner developed by UK-based Kromek Ltd can analyze up to...

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