NOVELTY - A segmented metal hydride hydrogen gas storage system comprises hermetically enclosed containment can containing an electrochemical device. The device is connected to a hydrogen storage chamber (18) by a fluid communication piping. A dual one way check valve (30) is provided in the piping to permit reversible hydrogen gas stream flow between the device and chamber in one direction at any time.    USE - As metal hydride batteries having hydrogen storage capacity and to provide passive purification of hydrogen stream.    ADVANTAGE - The system inhibits water vapor migration into the hydrogen storage chamber and also inhibits migration of oxygen and other gas impurities when the system is dormant. The valve does not impede normal flow of hydrogen gas between battery and chamber during regular operation of the system.    DETAILED DESCRIPTION - A segmented metal hydride hydrogen gas storage system comprises hermetically enclosed containment can. An electrochemical device housed in the containment can and a hydrogen storage chamber (18) which are mutually connected by a fluid communication piping. The electrochemical device consumes hydrogen gas by a reversible electrochemical reaction. The hydrogen storage chamber has the metal hydride capable of releasably absorbing and discharging gaseous hydrogen. The metal hydride stores a concentrated volume of hydrogen. A dual one way check valve (30) is provided in the piping to permit reversible communication of hydrogen gas stream flow between the device and chamber in one direction at any time. The fluid communication direction depends on the pressure differential across the check valve being greater than a predetermined threshold pressure.    DESCRIPTION OF DRAWING(S) - The figure illustrates a schematic cross-sectional view of the segmented metal hydride hydrogen gas storage system.    Hydrogen storage chamber (18)    Dual one way check valve (30)    Constricted end (40)    Divergent end (42)    Ball (44)    Spring (46)