A size selective approach to improving selectivity in semiconducting metal oxides (SMO) sensors was obtained by tailoring the architecture of WO(3) powders. The key for achieving high selectivity is based on using a dual sensor configuration where the response on a porous WO(3) powder sensor was compared to the response on a nonporous WO(3) powder sensor. Detection selectivity between methanol and dimethyl methylphosphonate (DMMP) is obtained because the access of a gas molecule in the interior pore structure of WO(3) is size dependent leading to a size dependant magnitude change in the conductivity of SMO sensor.