Dear Ausama I. Khudiar;

The gas-sensing response, (R) is defined as the ratio of the resistance values of the sensor; in the detected gas to the resistance in the air; R = Rg/Ra. whereas the gas sensitivity is calculated by the following equation, S (%) =((Rg-Ra))/Ra×100, more details in the reference;

Wang, C. Metal Oxide Gas Sensors: Sensitivity and influencing factors, Sensors. 10, 2088–2106 (2010) https://doi.org/10.3390/s100302088.

Hi Dear;

Sensing response is the time taken for a sensor output to shift from its previous state to a final settled value while sensitivity is concentration of gas at which maximum response is seen.

The formulaR=Rg/Ro use it to calculate the response value

to calculate sensitivity use the formula S=Response/concentration.

Response of the sensor in general is the change in the sensor characteristic parameter. The response of the resistive sensors is well described above. The sensitivity of the sensor is frequently understood as the minimum detecting gas concentration (measured in ppm or ppb). Sometimes though the sensitivity may be understood the way described above, as the change of the measured parameter of the sensor divided by the change in the gas concentration (that caused the parameter change).

Li, Y., Chen, N., Deng, D., Xing, X., Xiao, X., & Wang, Y. (2017). Formaldehyde detection: SnO2 microspheres for formaldehyde gas sensor with high sensitivity, fast response/recovery and good selectivity. Sensors and Actuators B: Chemical, 238, 264-273.

Sensing response for particular gas concentration is calculated by using

R%= (Rg-Ra)*100/Ra. as many of the researchers have used. but sensitivity is defined (according to the IUPAC) as slope of the graph plot between the sensing response (in Y-axis) vs concentration (X - axis)., Thus

S=delta R/ delta C. and its unit will be ppm-1

please read this paper

doi.org/10.1007/s10854-020-04760-2

Response (R) = (|Rg-Ra|)/Ra, where, Ra, Rg are the stable values of the resistance of the material before and after exposure to gas.

Sensitivity is a change of measured signal per analyte concentration unit, i.e., the slope of a calibration graph. This parameter is sometimes confused with the detection limit

Response; it is the amount of change of the physical parameter in the presence of a certain concentration of gas.

Sensitivity; it is the response rate to the unit of concentration of the targeted gas.