Single electron transistor (SET)-based gas sensors utilizing tungsten nanoparticles as conducting islands and operating at room temperature have been fabricated. Electrical characterization showed a strong correlation between the drain current of the SET device and the concentration of gas. The reversible exposure to gas resulted in reduction of both the Coulomb blockade voltage and the drain current. The reduction in the drain current shows an oscillatory behavior, with the variation on the gate bias. The sensitivity of the gas sensor can be tuned by controlling the charge on the gate electrode. Relaxation times of 400 ms for a concentration of 36% of gas in were achieved. Although the SET sensor has not been demonstrated with sensitivities in the few tens of ppm compared with existing technologies, the response is very fast and the sensitivity can be tuned by modulating the gate bias. The sensor demonstrates the possibility of gas sensing using SET devices as sensitive electrometers. The sensitivity of the SET gas sensor is higher at lower concentrations.