Sorption and diffusion of water and methanol in polydimethylsiloxane and a series of PEBAX(TM) copolymers (polyether block amide copolymers) were measured over a wide range of activities near room temperature. The goal was to identify a membrane material for separation of the hazardous air pollutant methanol from wet air streams in the pulp and paper industry. The PEBAX(TM) copolymer series used here allows a unique insight into transport of small molecules, because solubilities are virtually constant, while diffusion coefficients vary. This is due to the similar chemical structure, but different chain mobility of the homopolymers. The grade PEBAX(TM) 2533 is most promising for the separation process due to high solubility and diffusivity. The unwanted simultaneous highly selective separation of methanol and water from the targeted air/vapor streams will be addressed in future work.