... thin film sensor exposed to methanal (HCHO) gas atdifferent operating temperatures (200, 300 and 400° C). In the gas- sensing test, HCHO gas was diluted in water vapor, and the flow velocity of ... Beijing, ChinaG. Yang Á P. Hu Á Y. Cao Á F. Yuan (&)State Key Laboratory of Multi-phase Complex System, Institute of Process Engineering, Chinese Academy of Sciences,100190 Beijing, Chinae-mail: ... HCHO gas passes the sensor, whichindicated the good response speed of fabricated gas sensor.As time increases, gas diffusion slows down in the film,leading to a corresponding slowdown of the...