In this work, we numerically simulated permeations tests on thin martensitic steel membranes using finite elements analyses to determine the behavior of hydrogen during desorption. Starting from a formal model of hydrogen diffusion, we considered cases with one or two kinds of trap sites. We noticed a delay in the desorption of the trapped hydrogen when the trap binding energy rises or when the untrapping jump frequency decreases. The lattice hydrogen may be free from the influence of hydrogen trapping during the desorption if the trapping phenomenon is too weak or too strong. By considering reversible and irreversible trap sites, we notice that the irreversible traps become predominant over the reversible traps. In that case, the lattice hydrogen and reversibly trapped hydrogen behave similarly and may be associated to "diffusible" hydrogen. Copyright (C) 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.