According to one aspect, a system for sensing ethanol from human skin, that comprises at least one apparatus for sensing ethanol and a coupling matrix readout extraction unit for performing a method of extracting a coupling-matrix readout. The at least one sensing apparatus and the coupling matrix readout extraction may be mounted on a substrate. The substrate may be adapted such that it can be formed into a wearable accessory that can be worn by a human subject. When the wearable accessory is worn by the human subject such that the subject provides a skin tissue sample to the accessory, the presence or concentration of ethanol and other compounds may be determined from the vapour associated with the tissue sample.