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Special Report: The virtual way to unpack liquids and laptops
The latest 3-D scanners installed at airport security channels mean ‘there is no way to conceal something’. Ian Taylor reports
The 3-D scanners which promise to transform the airport security experience once fully installed and certified by ending the 100ml restrictions on liquids, gels and aerosols are modelled on hospital scanners.
The liquids, laptops and other devices in air passengers’ carry-on bags are obviously very different from soft tissue – so how do the scanners, which Travel Weekly (August 14) reported being installed at most UK airports, work?
Richard Thompson, portfolios, innovation and digital vice-president at Smiths Detection which makes the only CT scanners currently approved for screening liquids of more than 100ml in bags, explained: “They primarily measure two things – density, whether an item is organic or non-organic, and the ‘Z effect’ [or effective nuclear charge] which is the atomic number of the item being scanned.
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“The [machine] algorithm basically asks, ‘Could that item be an explosive or not?’”
There is also a visual element, he explained, saying: “Is there a detonator? Are there wires? That is where the quality of the detectors, the quality of the X-ray generator, the resolution of the image, the quality of the software and the skill of the analyst come into play.
“So, there are two quite different methods of detection. One is ‘This looks like it could be an explosive’ – that is where you start. Then you try to spot knives or other weapons in bags.”
He noted: “You can get false alarms with boot polish, cheese and other items which share similar properties [to explosive].”
But Thompson said: “The benefit of CT scanning is it takes hundreds of images, so you end up with a 360-degree, three-dimensional render.
“Where in the past if there was a laptop or iPad on top of something suspicious, you might not be able to see through it. It would look too cluttered. With CT [computer tomography] you’re getting a 360-degree view. You can see underneath the laptop.
“The software is so advanced that an operator can remove the laptop from the image, virtually unpacking the bag.
“That is what allows passengers to leave stuff in their bags because there is no way you can conceal something as you might have been able to in the past. The security staff can see the whole bag from whatever angle they wish.”
The security upgrade is not cheap
The scanners are not cheap to purchase, install and maintain, with airports paying about £1 million per security lane to upgrade to them.
Thomson said: “If you look at the whole security checkpoint, you can spend as much on the body scanner, the trays, the tray-return system, the automation, the software and so on [as on the 3-D scanner]."
The cost of the scanners is commercially sensitive, but airports can be looking at spending £500,000 per security lane, if not more, just on the equipment. But that is just the start. The scanners come with service contracts, so the total cost can be close to £1 million per security lane.
Thomson admitted: “It’s not cheap but there is a return on investment because passengers get through a lot quicker and are happier.” The extra time in departures leads them to spend more, he suggested,
Some airports have had to reinforce buildings or install new lifts because of the scanners’ weight. Thompson said: “CT scanners are quite heavy, over two tonnes per machine, so airports need to factor that in, for example if security is on a mezzanine floor.
“[But] for most airports with security on the ground floor, it’s not an issue.”
He added: “Installing these is a major project because you can’t just shut an airport down, so they’re installed one by one.
“Heathrow is just finalising its installation programme. We secured that order in 2020 so it was a five-year project.”
Thompson noted: “There was a concern that it would take analysts longer to view bags and make decisions on 3-D images, but that has been found not to be the case.”
Next steps at security
Even the latest 3-D scanners reject 5%-10% of bags, sending them down what Thompson calls “the naughty lane” as security to be opened and searched manually. So, there is research into whether X-ray diffraction could improve the process.
Thompson said: “X-ray diffraction can give the precise molecular fingerprint of a substance, telling you ‘It’s not explosive, it’s cheese’, so the bag isn’t rejected.”
He noted: “We’re looking to improve the checkpoint with this on top of the CT system.” However, he said: “We would need to ensure it didn’t impact the bag flow.
For example, Gatwick works at up to 800 trays an hour per lane – passengers have to jog to catch up with thir tray. We can’t introduce technology that slows that down.”
The other technology in development is artificial intelligence (AI). Thompson said: “There is a strong argument that machines could do a better job than people. Software never gets tired.
“But it’s difficult for a government minister to say ‘We’re turning this all over to AI’ because of the one-in-a-million chance something goes wrong. There is political reluctance to deploy AI not just in the UK but around the world.”
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