Sensitive material of MQ131 gas sensor is O3 SnO2, which with lower conductivity in clean air. When Ozone gas exists. The sensor’s conductivity is more higher along with the gas concentration rising. Please use simple electro circuit, Convert change of conductivity to correspond output signal of gas concentration. MQ131 gas sensor has high sensitivity to Ozone, also sensitive to O3 CL2, NO2, etc.