shows the evolution of the signals generated by TGS 825 sensor. Each line represents the
average signal variation of all VOO samples. It can be seen that the sensor signals reach a plateau after a
certain time (10 min). However, TGS 821 sensor, with a conductance change near zero, was not used for
data analysis. To analyze the response of the e-nose, three meaningful parameters were extracted from
each sensor conductance response: the steady-state conductance, the dynamic slope of the conductance
and the area below the conductance curve. The features coming from the sensor array measuring in
different samples are treated using pattern recognition techniques, such as the Principal Component
Analysis (PCA) and Linear Discriminant Analysis (LDA)