Headspace Particulate Measurements of Low Vapor Pressure Inorganic Oxidizers for Detection Canine Disciplines

Fuel-oxidizer mixtures are popular energetics in homemade explosive devices composed of an oxidizer and a fuel. To date, detection canines remain one of the most successful tools for detecting the illicit usage of these materials. However, some popular inorganic oxidizers, such as potassium chlorate, have little to no anticipated vapors due to their negligible vapor pressures. There is subsequently an ongoing question in the detection canine discipline regarding what chemical(s) are enabling odor recognition. The goal of this study is to help improve our understanding of the chemical signatures that may be involved, focusing on measuring headspace particles to complement the existing knowledge on vapor. Measurements were collected on both bulk (grams to pound) and trace (micrograms) sample quantities. Nanometer- to micrometer-diameter particles were observed to be liberated, including those that could deposit in the nasal olfactory region. Aerosol mass spectrometry analysis observed signals for potassium, chlorine, hypochlorite, and chlorite. Vapor analysis observed signals for other volatile organic compounds. Vapor analysis results are consistent with expectations that potassium chlorate has a negligible vapor pressure and contributes minimally to the overall vapor composition. Headspace particulate analysis results suggest a possible event chain for odor perception, starting from surface particles to liberation into the headspace and then deposition in the nasal cavity for sensing. The implications of such events for canine odor recognition training for inorganic oxidizer detection are discussed.