The dependence of the readings of four different Pirani vacuum gauges on nine different gas species was investigated. It was found that the gas species dependence varied from gauge to gauge so that in general only an approximate correction factor for a specific gas species can be given for this type of vacuum gauge. A Pirani gauge produced by microstructuring methods showed a broader measurement range than conventionally produced gauges. By comparing experimental with theoretical data, it was possible to give upper limits of the thermal accommodation coefficients of the nine gas species on the technical surfaces of oxidized tungsten and silicon within the gauges. (c) 2008 American Vacuum Society.