Solvent diffusion studies are often conducted in sorption columns, and the progress of sorption is followed by recording the weight gained by the polymer sample. While precautions are taken to achieve isothermal conditions, instantaneous pressure change, etc., some of these effects during solvent sorption into a polymer film cannot be avoided. Depending on the conditions of sorption, the measured and actual diffusion coefficients may differ considerably. In this work, we developed a model to describe solvent sorption with coupled heat effects and non- instantaneous pressure change into a slab, with a view to correcting the experimental data to obtain accurate measurements of diffusion coefficients.