Development of a new sampling device for hazardous gases and vapors in work environments with a built-in breakthrough detector using semiconductor gas sensors

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Charcoal tubes are widely used for measuring organic vapors in work environments, but it is impossible to know the breakthrough of the vapors during the sampling. In this study, a detection method of organic vapors was developed by using semiconductor gas sensors.Organic vapor was introduced into a glass column equipped with two sensors and the resistance of the sensors was monitored. After the system became steady state, a charcoal tube was attached to upstream of the sensors. The resistance of the sensors was collected temporally to an IC card. The vapor concentration of the exhaust air near the sensors was measured with a FID-gas chromatograph (GC) at intervals of 5 min to obtain the breakthrough curve.When the relative humidity was 0%, output signals of the sensors began to change before the breakthrough was recognized for all of tested organic vapors, that is, acetone, methyl ethyl ketone, methyl acetate, ethyl acetate, methanol, IPA,toluene, 1-butanol, dichloromethane, chloroform and 1,1,1-trichloroethane. When the relative humidity was 80%, the sensors could also be detected the vapor before the breakthrough was recognized for many organic vapors, but the breakthrough of the vapor cannot be detected for dichloromethane and chloroform.Based on the above results, an alarm system that can inform the breakthrough of a sampling device was developed. The developed system can detect the breakthrough of many organic vapors, so that it will become to be useful for an indicator of the sampling limit in charcoal tubes.