Strategies to avoid VOC cross-sensitivity of SnO2-based CO sensors

CO gas sensors have to fulfil the requirements of standards Like the UL2034 or BS7860. These standards require negligible interference in cross sensit ivity tests of CO gas sensors. Besides their CO sensitivity, tin oxide gas sensors are also cross sensitive to volatile organic compounds like long ch ain hydrocarbons, alcohols or ethyl acetate. To fulfil the standards, charc oal filters are used combined with a micromachined SnO2 sensor. The latter is operated in a pulsed mode. Optimized size and material parameters of the charcoal filters protect the sensor from long chain hydrocarbons and alcoh ols. Small reducing molecules can be distinguished from CO by mode of opera tion and a suitable multi component analysis. Sensors with a combination of both methodologies fulfil the standards. The sensors are characterized by electrical measurements as required by the standards. The filters are chara cterized by SEM, EDX, BET and TG/DSC. (C) 1999 Elsevier Science S.A. All ri ghts reserved.