The recognition element of a gas sensor often suffers from cross-sensitivity : gas species besides the analyte, interferents, also interact with it and contribute to its response. Variance in the concentration of an interferent, if uncorrelated with that of the analyte, "breaks"/weakens/corrupts/confounds the correlation between the response of the cross-sensitive sensor with the concentration of the analyte. For example, isoprene strongly interferes with the response of a chemoresistive Si/WO 3 sensor to acetone , making it impossible to use such a sensor to distinguish between increases in acetone vs. isoprene in human breath .