Filters for tin dioxide CO gas sensors to pass the UL2034 standard

CO gas sensors have to fulfil the requirements of standards like the UL2034 or BS7860. Unfortunately, tin oxide gas sensors are also highly sensitive to volatile organic compounds (VOCs) like long chain hydrocarbons, alcohols or ethyl acetate. These standards require negligible interference in cross-sensitivity tests of CO sensors. To fulfil the standards, charcoal filters were used combined with a micromachined SnO2 sensor. The latter was operated in a pulsed mode. Sensors with optimized size and material parameters of the charcoal filters are shown to fulfil the UL2034. The sensors are characterized by electrical measurements as required by these standards. The filters are characterized by SEM, EDX, BET and TG/DSC.