When a bomb-sniffing canine encounters an explosive, it inhales a multitude of small organic molecules, which interact with the olfactory receptors in the nasal mucosa to induce a neurological response. In short, the dog takes in the volatile compounds given off by the target, and if they smell familiar, it recognizes them. One such compound, given off by C-4 and other plastic explosive formulations, is 2-ethyl-1-hexanol (2E1H). Research has shown that 2E1H dominates the headspace above C-4, and dogs trained on C-4 have alerted to 2E1H in previous studies, just as they would for an actual explosive. Due to their apparent likeness of odor, some have proposed using 2E1H as a substitute for genuine C-4 when training dogs to detect plastic explosives. Using gas chromatography-mass spectrometry with solid phase microextraction as a pre-concentration technique, we demonstrate that while 2-ethyl-1-hexanol does indeed off-gas from authentic Composition C-4, it is also is found in the headspace of several common plasticizers, such as bis(2-ethylhexyl) adipate, bis(2-ethylhexyl) sebacate, and bis(2-ethylhexyl) phthalate (DEHP). This may potentially discourage its use for training purposes, as many plastic items common to everyday life contain similar plasticizers that could conceivably off-gas 2E1H as well, potentially contributing to canine false positive alerts.

On the smell of composition C-4

246th National Meeting (2013)

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