Detection of Chemical Warfare Agents in the Presence of Interfering Materials

Abstract

The performance of two portable chemical warfare agent (CWA) alarm units, AP2CV (Proengin France) and M90 (Environics, Finland), challenged with CWA and interfering materials, was evaluated in the laboratory. This study focuses on the effect of fuel vapors and carbon dioxide on the detectors' responses to sulfur mustard (HD) and sarin (GB) vapors. The interfering materials were chosen to simulate battlefield scenarios such as fuel spills and use of fire extinguishers. In general, CWA alarm units should have a fast and accurate response so that false negative (FN) or false positive (FP) alarm rates will be low. Although both detectors detect CWA within a few seconds, their selectivity is not the same. The false alarm rate of the AP2CV is low, suggesting that dual wavelength flame photometric detection (FPD) is a reliable technique for CWA alarm devices. The M90 is a “consumable free detector” that incorporates two sensors: atmospheric pressure chemical ionization (APCI) and semiconductor cell (SCC). We found that the false alarm rate is high in the presence of fuel vapors. Addition of CO2 did not cause FP alarm, did not mask GB, and unexpectedly increased the sensitivity to HD. The physical and chemical processes involved in the detection of CWA/interferants mixtures by the AP2CV and M90 are discussed.