This work demonstrates the feasibility to measure accurately low level of CO concentration diluted with synthetic air and two other gases (C 3 H 8 and NO 2) with only one SnO 2 micromachined gas sensor. By consideration of the shape and time constants of the normalized response curves correlated with chemical reactions, it is possible firstly to discriminate different gas mixtures and secondly to evaluate one of the present gas at a ppm level by using two successive Linear Discriminate Analysis (LDA) based on specific variables.