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Quantification of Hydrogen Cyanide Generated at Low Temperature O-Chlorobenzylidene Malononitrile (CS) Dispersal

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Technical Report

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Uniformed Services University Of The Health Sciences Bethesda United States

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Hydrogen cyanide HCN is an acutely toxic airborne chemical compound Immediately Dangerous to Life or Health IDLH 50 parts per million ppm and has been previously determined to be a thermal degradation by-product of the riot control agent o-chlorobenzylidene malononitrile CS. Previous research and studies conducted by U.S. Army and Air Force in mask confidence chambers demonstrated quantifiable airborne HCN levels released into the atmosphere at CS combustion temperatures of 350to 800C. Presently, many CS confidence chambers exist in the military for training purposes and CS thermal combustion aerosolization processes are known to vary widely amongst these different sites. As such, the combustion temperature achieved maybe impacted, and thus, the airborne concentration of HCN generated may be impacted, creating a potentially higher or lower HCN level depending on the combustion temperature. Given this procedural variability, this study focused on determining the range of combustion temperatures in which HCN is generated. Particular focus centered on identifying if HCN is generated at combustion temperatures as low as 100 C and if the levels quantified exceed established occupational exposure limits OEL, such as the NIOSH Recommended Exposure Level REL-Short Term Exposure Limit STEL of 4.7ppm, and Military Exposure Guidelines MEGs. This study quantified airborne HCN levels generated in both the field, at live CS training events at Ft. Jackson, SC, and in the laboratory using a tube furnace operated at discrete CS combustion temperatures over a range of 100 C to 350 C. Study findings indicate that HCN is quantifiable even at 100C, much lower than previously hypothesized, but well below the OEL and MEGs. Findings may assist in standardizing DoD doctrinal policies related to thermal combustion processes within CS chambers.

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