For more realistic description of vapor permeation through polymeric membrane it is desirable to replace the experimentally readily accessible data on the permeate equilibrium sorption with a difficult to obtain information on the actually sorbed amount at the steady state operation of the process. For this purpose, we designed a new apparatus making possible performing permeation and steady state sorption experiments practically simultaneously. This novel experimental approach was tested in a study of propan-1-ol transport through a low-density polyethylene (LDPE) membrane in a range of experimental conditions (membrane thickness, feed concentration, temperature). Fluxes calculated using Fick's first law equation from the evaluated transport parameters (diffusivity and concentration gradient) agreed very favorably with the experimental flux values. (c) 2005 Elsevier B.V. All rights reserved.