Airport laser interrogator gives you back your bottle

Sick of having to ditch your bottled water, booze and toiletries at the airport security post? That appalling hassle should end by April next year, when airports are supposed to start screening the contents of bottles for explosives.

But they can only do this if the bottle-scanning technologies currently being trialled are up to the job. This week, Cobalt Light Systems of the UK says its explosives detector has passed all its European civil aviation security tests - which means the end should be in sight for bottle-dumping at airport security.

The rule that no bottles larger than 100 millilitres can be carried on aircraft followed the failed 2006 attempt by 17 would-be terrorists who conspired to carry hydrogen peroxide-based liquid explosives onto aircraft in Britain.

The key to getting rid of the subsequent ban on all but the tiniest bottles is revealing what bottles contain without opening them. Cobalt Light Systems - a spinoff from the Central Laser Facility in Harwell, UK - uses a microwave oven-sized machine that uses a near-infrared laser to interrogate the liquid, powder or gel molecules in a bottle and reveal what they are chemically.

The technique, called spatially offset raman spectroscopy, shines the near-infrared laser into the bottle at a number of points. A small proportion of the light reflected back at each point is shifted in wavelength by the energy levels in the liquid molecules, and this small shift reveals what the substance is. Within five seconds of placing a bottle in the machine, a simple readout says: "marmite" or "hydrogen peroxide". See a video of the machine in action.

Crucially, Cobalt's newly-approved technology has a low rate of false alarms - it gives less than 0.5 per cent false positives - and reveals the seemingly innocent precursor chemicals that could be mixed inflight to create a potent explosive, says CEO Paul Leoffen.