The application of polymeric membrane in combination with the metallic films can be used for the gas purification; in particular, the hydrogen where the molecular size is very small. The affinity of hydrogen to certain metals assists the flow of hydrogen, however, restricts the permeation of other gases. However, the flow rate is very small in the dense membranes. Attempts have been made to etch the nuclear tracks of the polymeric membranes in a very controlled way to achieve the conical etched tracks to meet the vertex. This has been characterized by gas permeation measurements. (C) 2003 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.