A holistic approach for evaluating liquid explosive detection systems

Abstract

European legislation requires airports to screen liquids, aerosols, and gels by 31 January 2014. As a variety of devices can be used for that purpose, airports have to evaluate which devices best suit their needs. In order to so, a holistic “three-pillar approach” was designed and applied at a large European airport in order to evaluate all six “type B” liquid explosives detection systems that are currently certified and available. The “three-pillar approach” consists of laboratory tests, field tests, and stress tests. The laboratory tests aimed at evaluating the devices under standardized conditions. Field tests were conducted to analyze the devices’ performance and human-machine-interaction aspects in the real environment. The aim of the stress tests was to find out more about how the devices might perform upon a further lifting (phased approach) of the ban of liquids in hand baggage. The three-pillar approach could successfully be applied. The results from all three pillars differed with regard to their outcome variables and the information gained. The operational performance (false alarm rates and range of use) of the devices differed significantly between different devices and depended on the sample of liquids screened. Furthermore, some devices differed significantly regarding their false alarm rates between laboratory and field setting, which could be attributed to the usability of the devices. Security Officers’ overall impression and trust in the devices depended on the false alarm rates and the usability of the devices. At present, the amount of liquids carried by passengers is too small to have a significant influence on operation. However, the stress tests showed that an impact of the screening of liquids on operation has to be expected if passengers bring more liquids to the security control checkpoints. The results imply that human factors, as well as the environment in which devices are implemented, influence the performance of liquid explosives detection systems and should therefore not be underestimated. This again stresses the importance of a holistic evaluation of security technology with different methodologies.