General Comments on Detection of Explosives

The past decade may be characterized by an intense research effort to improve the sensitivity and reliability of ion mobility-based instruments for detection of explosives and to expand the inventory of detectable explosive substances. In addition, improvements in sampling techniques have been proposed, standards for calibration of ion mobility spectrometry (IMS) instruments and for method verification have been developed, and novel instrumental techniques based on laser ablation or electrospray ionization have been advanced. This has occurred due to the rising need for rapid, efficient, and reliable detectors of explosives that are used in acts of terrorism worldwide, as stated in many occasions (see Rame 12.1). Some idea about the scale of this trend can be gained from a recent report Austin, TX, 15 Septanber, 2011—Sales of Explosives, Weapons, and Contraband (EWC) Detection equipment to the world s airport authorities, amassed a significant 834.9 million in 2010, according to a recent study published by IMS Research, a leading provider of market research in the homeland security industry.  

The following is from Dana A. Shea and Daniel Morga, Detection of Explosives on Airline Passengers Recommendation of the 9/11 Commission and Related Issue, CRS Report for Congress, Order Code RS21920, Updated April 26, 2000  

A different researeh ehaUenge is the deteetion of novel explosives. Detectors are generally designed to look for speeifie explosives, both to limit the number of false or innoeuous positives and to allow a determination of whieh explosive has been detected. As a result, uovel explosives are unlikely to be detected until identifying characteristies and reference standards have been developed and incorporated into equipment designs. Unlike imaging techniques for deteeting bulk quantities of explosives, trace analysis provides no opportunity for a human operator to identify a suspieious material based on experience or intuition. 

Liquid explosives are a novel threat that has been of particular interest since August 2006, when British poliee disrupted a plot to bomb aircraft using liquids. The DHS is evaluating technologies to detect liquid explosives. Its efforts are mainly focused on bulk detection, such as scanners to test the contents of bottles. Like solid explosives, however, liquids might be found through trace detection, if the trace detection system is designed to look for them. 

Explosive detection methods with high reliability must have a low false-positive rate (below 2% is the recommended goal) and a practically zero false-negative rate. In addition, to be certified the system should be sensitive and fast enough to detect the explosives rapidly so that ideally 7-10 passengers could be screened in a minute 

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