A thermoelectric 'nano-nose' has been built from tangled bundles of single-walled carbon nanotubes (SWNT). The response is specific to the details of the interaction of the adsorbed molecule with the nanotube wall; even gases such as He, N-2 and H-2 can be easily detected. Plots of DeltaS vs. rho (a) are sensitive to whether oxidation or reduction of the tube wall is taking place, and to whether the gas molecule is physisorbed or chemisorbed.