Discrimination of Volatile Organic Compounds in Indoor Environment by an Integrated Thick-Film Gas Sensor

Recently, sick-house syndrome receives public attention as a problem of indoor environment. Volatile organic compounds (VOC) such as formaldehyde (HCHO) and toluene (C6H5CH3) generated from building materials are pointed out as one of the main cause of sick-house syndrome. In order to develop semiconductor gas sensor available to discriminate chemical species of these VOC, integrated thick-film gas sensors which are composed of SnO2, WO3, In2O3, ZnO, Co3O4 and Cr2O3 was fabricated on Al2O3 substrates. The present study was focused on examining the possibility of this sensor to discriminate 17 chemical species in VOC by pattern matching method using polar plots. First, the polar plots were constructed for each chemical species. These plots were classified into 7 groups, each of which has a characteristic shape depending on the functional group of chemical species. Next, the polar plots response time of SnO2, WO3 and In2O3 were also constructed for several chemical species. They were classified into three types of patterns. The polar plots obtained by the measurements of mixed VOC with known concentration were almost consistent with that of expected pattern The combination of the polar plots of both sensitivity and response time will assist the precise discrimination of chemical species in VOC.