A new gas/vapor mixture permeation system is described to investigate the effect of organic molecules on oxygen (O2) and carbon dioxide (CO2) transport in barrier materials. Methanol vapor was considered as a flavor simulant mainly because of its conveniently high diffusion coefficient, which makes the experimental time accessible. A highly accurate syringe pump was used to introduce a desired activity level of vapor into gas feed stream. Adsorption of methanol on high energy surfaces is carefully characterized to prevent underestimation of methanol permeability. A special permeation cell was also developed to study the effect of interacting vapors on O2 and CO2 transport in barrier materials. Systematic permeation measurements were conducted for binary and ternary gas/vapor permeation measurements (e.g., MeOH/O2 and O2/CO2/MeOH) to verify the feasibility of our new vapor/gas permeation system. (c) 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012