“…Different types of sensors may be used to detect volatile substances in the gas phase. Metal oxide sensors (MOS) (tin oxide, SnO 2 ; zinc oxide, ZnO; and tungsten oxide, WO 3 ), which may or may not be doped with precious metals (especially palladium, Pd, and platinum, Pt), have been used for many years in gas detection and have provided the basis of many new research developments (Seiyama, 1978;Windismann, 1979;Oyabu, 1984;Moseley and Williams, 1987;Oishi et al, 1988;Gardner, 1989;Mosely and Williams, 1991). Their ability to detect aromas and discriminate among them has been tested in many fields, particularly in the agrifood industry (Moy, 1992;Gardner et al, 1992a,b;Moy, 1993;Moy and Chatonnet, 1993).…”