Preliminary evaluation of an active end-of-service-life indicator for organic vapor cartridge respirators

Data are presented on a microwatt chemiresistor microsensor for use with negative-pressure organic vapor respirators. This sensor would operate at or within a sorbent bed and detect parts per million levels of chemical vapors and/or gases as a function of sensor resistance. Sensors were evaluated against four challenge concentrations of ethyl acetate (750 ppm, 1000 ppm, 1500 ppm, and 2000 ppm). Direct comparison of breakthrough times and curves for the chemiresistor microsensor and a standard infrared (IR) detector system were made. The chemiresistor sensor responses were found to correlate well with the IR system. The evaluation showed that although the chemiresistor sensors were not as sensitive as the IR detectors, they could be used if located inside the charcoal bed. Thus, these sensors could function as organic-vapor detectors and could be used in cartridge applications. However, further improvements in stability and sensitivity of these chemiresistor sensors is necessary.