Provided is a system for detecting analytes of interest present in a gas sample, including a layer of porous material, positioned at the surface of a substrate so as to extend longitudinally along a fluidic flow path of the gas sample, said porous material containing a plurality of probe molecules, each probe molecule being able to react with the analyte of interest by causing a change in the spectral properties of said probe molecule. Also included is a a pump for generating a flow of the gas sample along the fluidic path so that the gas sample comes into contact with said layer of porous material. The system also includes at least one optical detection device capable of successively detecting, at distinct detection areas of said porous material layer distributed along said fluidic path, a change in the spectral properties of at least one of said probe molecules.