In order to select and to apply a porous membrane under supercritical conditions, it is necessary to understand the transport mechanism affecting the permeation behaviour. This paper describes the investigation of gas transport through micro porous ceramic membranes consisting of several layers. The separation layer is made from TiO2 with a nominal pore size diameter of 0.9 nm Single. gas permeation of helium, nitrogen, argon, methane, and carbon dioxide was measured in the temperature range of 293-443 K and in the pressure range of 1-10 MPa. Observation of the permeability of these membranes revealed that the transport of non adsorbing gases under these conditions is governed by Knudsen diffusion and viscous flow. (C) 2009 Elsevier B.V. All rights reserved.