Explosives, detection

S. Block W. Leppehneir, Hazards Evaluation of the Explosives Detection... 

Based on its recent experience in facilitating the deployment of explosives-detection equipment at airports around the country, DHS s Transportation Security Administration (TSA) has established relationships with local airport authorities and is the agency most knowledgeable about U.S. 

To explore the capability of OFRR-based pGC in explosive detection, 2,4-dinitrotoluene (DNT) is chosen as a model system, due to its chemical structure... 

Aspects of Explosives Detection M. Marshall andJ.C. Oxley (Editors)... 

Table i Terrorist attacks influencing US explosive detection efforts... 

Criminals and mentally disturbed or immature persons are both likely to be limited by the availability of materials and knowledge. In addition, criminals are quite likely to be more susceptible than the other groups to deterrence by visible and effective security measures. Thus, the first two groups — state-sponsored actors and non-state-sponsored terrorists — are the main threats on which explosives detection needs to focus. Unfortunately, this conclusion implies the need for detection of military, commercial, and improvised explosives and does not greatly help in narrowing down the issues. 

Human factors need to be properly considered in the design and appfication of any detection system. Studies have shown that explosive detection systems generally perform less effectively in realistic field trials than in laboratory tests and that one of the biggest causes of this shortfall is failure to properly consider the operator/ system interface. 

The requirements for an explosive detection system are set out in certification standards issued by the FAA/TSA/DHS. Key issues are as follows ... 

Many of the original puzzles and concerns considered before initial deployment of explosive detection equipment have not been resolved, but less than optimal solutions have had to be accepted. For example, an alarm is usuaUy resolved by re-screening of the object, hand examination of the alarming item, or questioning of the owner. None of the presently fielded techniques address the need to determine whether a liquid threat material has been sealed in a bottle. There was a short period of time after the terrorist attacks of 11 September 2001 when people wishing to carry a bottle of liquid on board an airplane were required to take a sip of it to demonstrate it was innocuous. Since the threat from liquid explosives in the... 

A. Fainberg, Explosive detection for aviation security . Science 255 (1992) 1531—1537. 

V.T. Mikhaltsevitch and A.V. Beliakov, Polarization enhancement of NQR signals for explosive detection , Sohd State Commun. 138 (2006) 409—411. 

Existing and Potential Standoff Explosives Detection Techniques , National Research Council, Board on Chemical Sciences and Technology, 2004. 

Most explosive detection equipments do not truly detect explosive vapour, rather they key on minute particles of the explosive [11]. The reason for this is that most explosives have very low vapour pressure, and low vapour pressures are rather difficult to measure. Methods based on mass loss or the direct measurement of tiny pressures are particularly prone to the influence of trace impurities of more volatile substances. Consequendy, the values reported in the literature exhibit a high degree of scatter. To add to the confusion, difierent units of measurement are used. In general, measurements involving chemical determination of the amount of the specific compound in the vapour phase are to be preferred. If several difierent values are reported, and there is no better criterion for selection, it is probably best to take the lowest value. 

Increased vigilance regarding security to protect against terrorist use of weapons of mass destruction, including especially explosive devices, as well as an increased interest in the comparison to the explosive detection capabilities of instrumental technologies, has led to increased scrutiny of canine explosive detection capabilities. 

Presently, US explosives detection dogs tend to be German or Belgian Shepherds, Malinois or Labradors, but there is more variation within a breed than between breeds [22]. Selecting a dog or breeding a dog with optimal olfactory capabilities has only recently been emphasized. Yet, for centuries animals have been bred to perform select tasks. Perhaps olfactory detection has lagged behind in this... 

M. Williams, J.M. Johnston, P. Waggoner, J. Jackson, M. Jones, T. Boussom and S.F. HaUoweU, Determination of the canine detection odor signature for NG smokeless powder , Proceedings of the Second Explosives Detection Technology Symposium and Aviation Security Technology Conference, Atlantic City, N.J. Federal Aviation Administration, 1997. 

I. Gazit and J. Terkel, Domination of olfaction over vision in explosives detection by dogs , Appl. Anim. Behav. Sci. 82 (2003) 65—73. 

ATP, Odor Recognition Proficiency Standard for Explosive Detection Canines, 2005. 

Following the Birmingham Six case, the Griess test has become somewhat discredited by the forensic community. It should be emphasized, however, that when properly used, it is an excellent tool which can serve as a basis for an efficient field test. An explosive detection kit (ETK (explosive testing kit)), partly based on the Griess test, was successfully used in Israel in several terror and non-terror investigations [49] (see below). 

---