manifold flowing fluid from the channel 115 through the flow distributor 114 communicates with a chamber 120 and a chamber 121 communicates with the channel 116 through flow distributor 113 the chamber is defined by the concave feature of the sealing boss as well as the adsorbent retainer plate 122 which is supported by a snap ring 123 the psa apparatus of fig3 and 4 is shown for the case with the inlet manifold on the bottom of the apparatus and the outlet manifold on the top if the apparatus is mounted in the opposite direction the snap ring 123 would be on the other side of the retainer plate the retainer plate 122 may advantageously be supplied with a fine mesh layer 124 to retain small diameter adsorbent particles this mesh layer may be made from wire mesh woven or non woven polymer glass or other fabric the mesh layer 124 and the retainer plate 122 are preferably assembled with a radial seal ring 125 which holds them together for assembly and provides a radial seal to prevent bypassing of fluid or particles although this composite retainer assembly is preferred other adsorbent support means may be used with equal success such as metal polymer or ceramic foams with an open structure nonwoven mats or other means apparent to one skilled in the art the outlet manifold is preferably supplied with a similar retainer plate assembly except that the snap ring 123 is positioned to hold the retainer plate from above it is most preferable to supply an elastic layer 130 between the upper retainer plate and the adsorbent this elastic layer is then held in compression.