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

炭管被广泛用于测量工作环境中的有机蒸气，但在采样过程中不可能知道蒸气的突破情况。本研究利用半导体气敏元件建立了一种检测有机气体的方法，将有机气体引入装有两个传感器的玻璃柱中，监测传感器的电阻。在系统进入稳定状态后，在传感器的上游连接一根木炭管。传感器的电阻被暂时收集到IC卡上。当相对湿度为0%时，传感器的输出信号在所有被测有机气体(丙酮、甲乙酮、乙酸甲酯、乙酸乙酯、甲醇、异丙醇、甲苯、正丁醇、二氯甲烷、氯仿和1，1，1-三氯乙烷)被识别之前就开始发生变化。当相对湿度为80%时，传感器也能检测到许多有机蒸汽突破之前的水蒸气，但对二氯甲烷和氯仿则无法检测到突破，基于以上结果，研制了一种能够通知采样装置突破的报警系统。该系统可检测多种有机蒸气的突破，可作为炭管进样限值的指示器。

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.