Our research work aims to develop a microfluidic system for gas analysis by using an original principle of integrated pumping. This microsystem can detect ammonia and the gas flow parameters inside the channel can be also controlled. The proposed microdevice consists in a microchannel including an integrated gas sensor with a heater. The trioxide tungsten (WO 3) is implemented as a sensitive layer. The integrated heater is used for two reasons: to optimize the sensor response and to induce the gas pumping inside the microchannel by thermal creep phenomenon, therefore, no external pumping system is required. The study of the pumping effect generation has been realized by thermal and microfluidic simulations. Thermal simulations have been performed to estimate the thermal gradient along the microchannel. In addition, the microfluidic modelling allows us to determine the mass flow rate for different thermal gradient profiles, obtained from the thermal simulations. Finally, a complete Pyrex microsystem has been realized to detect ammonia. The existence of the thermal pumping has been demonstrated experimentally.