Thin films of tin oxide (SnO2) have been deposited by means of RF sputtering from a pure SnO2 target onto alumina substrates in an Ar/O-2 mixture. Different oxygen contents in the sputtering atmosphere were used, in order to achieve the best thin films properties for CO detection. Films with the best sensitivity were obtained with 30% oxygen. The optimum operating temperature of the realized devices was about 270 degrees C. Copyright (C) 1996 Elsevier Science Ltd