Hydrothermally grown hexagonal WO3 nano-rods were sensitized by additional Pt and Au nano particles. The size of the 20-29 nm noble metal nano-particles were stabilized with methoxypolyethylene glycol, and their solution was mixed with the tungsten-oxide nano-rod suspension. Controlled sized suspension drops of activated and pure reference material were deposited on the top of micro-hotplate with gold interdigital electrodes on top. The gas sensitive properties were measured for NH3 and H2S in a temperature range of 140-300 degrees C. Noble metal nano-particles multiplied the gas sensitivity for H2S, whereas no significant effect could be detected for NH3. With gold nano-particles a lower detection limit of 25 ppb could be achieved. The response time is in the range of 30-80 s, whereas typically 300 s is needed for complete recovery. (C) 2016 Elsevier Ltd. All rights reserved.