Last week, terrorists walked into Brussels' Zaventem airport and detonated bomb-laden luggage in the check-in area. They also bombed a subway station. As New Scientist went to press, 35 people had been killed and hundreds wounded. Can we stop attacks like this? Airport security focuses on keeping explosives off planes. Stopping bombs detonating in crowded check-in areas and transit terminals is a bigger challenge. Security checkpoints work, but they cause delays and create queues that can also be a target. But there are new ways to scan people as they walk. Cameron Ritchie, head of technology at the US-based security firm Morpho, is working on a "tunnel of truth". Passengers would be scanned by an array of sensors as they walk through the tunnel to get into airports or train stations. The Lincoln Laboratory at the Massachusetts Institute of Technology has a different approach. A team there has turned to lasers to "sniff" explosives from a distance. The lab says it can scan spaces like check-in areas from 100 metres away by sweeping them with lasers tuned to frequencies that vaporise molecules found in bombs. This material makes a tiny sound as it vaporises, which is amplified and detected.
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