The nanosized TiO2 was mixed with WO3 and doped with transition metals (Pt,Ru, Pd and In). Particle sizes, phases and specific surface areas of sensor materials were investigated by SEM, XRD and BET analyses. The metal-TiO2 thick films were prepared by screen-printing method onto Al2O3 substrates with platinum electrode. It was shown that the highest sensitivity and selectivity of the sensor for trimethylamine and ammonia mixed gas by doping with 1 wt.%In and 15 wt.% WO3 was
reached at the optimum operating temperature of 350 C.