In many actual applications of catalytic combustion, catalysts are coated on the channel and have a porous structure. Although numerical simulation for the optimal design of a reactor requires boundary conditions, it is not easy to obtain the concentration of radical species in the experiment; in addition, the measurement within a porous structure is even more difficult. This research considers the requirements imposed on the boundary conditions of a porous catalyst in which diffusion and reaction occur, particularly in the case with an elementary reaction scheme of hydrogen oxidation on platinum. When the concentration fluxes are given at the interface between the gas stream and the catalyst layer, reaction formulae restrict the number and type of boundary conditions. On the other hand, when the concentration is set as the boundary condition, slight differences in concentration may significantly affect the overall reaction rate. On the basis of the above findings, the features of several models were summarized. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.