Hey all,

I've got a question regarding the calibration function in https://github.com/empierre/arduino/blob/master/AirQuality-Multiple_Gas_Sensor1_4.ino :

$ grep MQCalibr *
AirQuality-Multiple_Gas_Sensor1_4.ino:  Ro0 = MQCalibration(MQ2_SENSOR,10,RL0,SmokeCurve);
AirQuality-Multiple_Gas_Sensor1_4.ino:  Ro1 = MQCalibration(MQ6_SENSOR,10,RL1,LPGCurve);
AirQuality-Multiple_Gas_Sensor1_4.ino:  Ro2 = MQCalibration(MQ131_SENSOR,10,RL2,O3Curve);
AirQuality-Multiple_Gas_Sensor1_4.ino:  Ro3 = MQCalibration(TGS2600_SENSOR,10,RL3,C2H5OH_terCurve);
AirQuality-Multiple_Gas_Sensor1_4.ino:  Ro4 = MQCalibration(MQ135_SENSOR,10,RL4,CO_secCurve);
AirQuality-Multiple_Gas_Sensor1_4.ino:  Ro6 = MQCalibration(TGS2602_SENSOR,1,RL6,C7H8Curve);
....
AirQuality-Multiple_Gas_Sensor1_4.ino:float MQCalibration(int mq_pin, double ppm, double rl_value,float *pcurve )

Th function MQCalibration should calibrate the sensor in clean air, the calibration function uses the PPM concentration of the gas in a clean air environment.
You already use the appropriate value for i.e. CO2 (around 399 PPM) in the MQ135 sketch - but why are you using those obscure values in the calibration (1, 10) here?

Thanks in advance!