Rules for liquids in hand luggage are being tightened again at airports throughout the European Union beginning on September 1, when passengers will once again be limited to containers of no more than 100 millilitres. Passengers are also required to pack liquid containers together in a single transparent plastic bag with a maximum volume of 1 litre. The liquid rules, which were introduced back in 2006, had been loosened at some German airport checkpoints if baggage could be checked using computer tomography (CT) scanners, which use a technology developed for medical scans that can quickly draw…