Review: Headspace components of explosives for canine non-detonable training aid development

Explosives detection canines are a versatile capability used to protect civilians and military personnel from concealed explosives, and their effective training requires exposure to the headspace odors of energetic materials. However, the hazardous nature of energetic materials presents challenges when training needs to be performed near other human activities. Non-hazardous, non-detonable training aids for explosives are useful for this purpose. To facilitate the design of these safer, alternative, training aids, this review summarizes the headspace components that have been measured from seventeen explosive targets: nitroaromatics (trinitrotoluene [TNT] and picric acid), nitrate esters (pentaerythritol tetranitrate [PETN], erythritol tetranitrate [ETN], dynamite, nitroglycerin, smokeless powder, and ethylene glycol dinitrate [EGDN]), salts (potassium chlorate, ammonium nitrate, and urea nitrate), black powder and sulfur powder, nitramines (1,3,5,-trinitro-1,3,5-triazine [RDX], including plastic explosives like Composition 4 [C-4]), and peroxides (triacetone triperoxide [TATP], hexamethylene triperoxide diamine [HMTD], diacetone diperoxide [DADP], and hydrogen peroxide). The compiled chemical vapors are separated based on how frequently they have been reported, and a list of the most widely observed compounds is provided. Additional meta-analyses found varying degrees of research interest across targets. For example, TATP and smokeless powder have more references than black powder and ETN. Most measurements are also qualitative, with solid phase microextraction gas chromatography mass spectrometry (SPME-GC/MS) being the most popular approach. From this review, summaries of headspace composition and characterization approaches are made available to facilitate the development and testing of canine training aids for explosives.