Year
2006
Abstract
Experiments have been conducted to investigate the contamination that remains on the exterior surfaces of vehicles after exposure to or loading with the explosives C-4, nitroglycerin-based dynamite, ammonium nitrate, and ammonium nitrate/fuel oil. These experiments were divided into two types: 1) vehicle exposure studies, in which a vehicle was exposed to trace explosive contamination and the effects of environmental factors on subsequent detection were investigated, and 2) vehicle loading studies, in which a vehicle was loaded with bulk explosive material and the impact of various human factors on detection of trace external contamination was investigated. Detection of the trace material was performed in all cases using ion mobility spectrometry (IMS). Explosive type, sampling method, explosive loading method, and presence or absence of a post-contamination car wash were found to have statistically significant impacts on the results. Other experiments were performed in which a lead vehicle containing 2,4,6-trinitrotoluene (TNT) pulled a mockup chase vehicle containing chemical preconcentrators to sample the plume of trace TNT material from the lead vehicle, with the results again being analyzed by IMS. Experimental variables included vehicle speed, TNT source-to-preconcentrator distance, temperature, wind speed, sampling time, and how the TNT source was covered or concealed. The results show that the TNT plume is detectable under many circumstances.