A thin-film tin oxide gas sensor was tested in a flow system for the sensitivity to each vapor (10, 10(2), 10(3) ppm in air) of methanol, ethanol, isopropanol, acetone and acetic acid. With a change in operating temperature, the sensitivity to each vapor went through a maximum around 450 degrees C. When compared at the same vapor concentration, the sensitivity was in the order of acetic acid > isopropanol > ethanol > acetone > methanol. This sequence was interpreted as resulting from the differences in ability to reduce tin oxide among the vapors. (C) 1999 Elsevier Science S.A. All rights reserved.