The sample to be tested is placed in a gas generator, and the gas generator carries out the sample gas and can control the flow rate of it. The sample gas flows into the mixing chamber, and the rotameter in the mixing chamber can confirm the gas flow once, and the mass flow controller is responsible for controlling the flow rate of the desorbed dry air. Both of them flow into the solenoid valve, and the gas can automatically adsorb and desorb by solenoid valve. Finally, sample gas flow into sensors. There are currently two commercial sensors (Figaro & MQ-3) and our surface acoustic wave gas sensors.