On-site detection of chemical warfare agents
Chemical warfare agents (CWAs) are low-molecular weight synthetic compounds, which are fast acting and sometimes lethal, even at low levels, and in physical properties can be classified into gaseous blood agents, gaseous choking agents, volatile nerve gases, volatile blister agents, nonvolatile vomit agents, and nonvolatile lacrimators. To measure the toxicity of a substance, a lethal concentration value is used. This value indicates the vapor concentration leading to 50% death in humans with 1 min inhalation. When considering toxicity manifestation time and vapor dispersion, the detection sensitivity for vapor concentration is one hundredth of LCt50 within 1 min. In the case of GB, this required detection sensitivity is 0.15 mg/m3, and at this level there is no odor and humans show no signs of toxicity. In the chemical weapon disposal situation, because the workers stay in one place for a long time, the time weighted average (TWA) values are the monitoring target for allowed operational conditions. These TWA values are approximately 1/100,000 of LCt50. The desired alarm time is to be less than several minutes. For portable-type detectors used by first responders, a combination of IMS and arrayed monitoring tape method machine is desirable. This combination covers gaseous to volatile CWAs. GC–MS helps to identify the detected CWAs. Nonvolatile CWAs are still unable to be detected by portable machines. For fixed-type detectors, highly sensitive detection equipment is necessary, and a combination of CFI-APCI-MS and a lined set of transmission-type monitoring tape method machines is almost perfect, covering all the CWAs with the required sensitivity.
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