NOVELTY - The gas-generating apparatus comprises a reaction chamber (58), a fuel mixture within the chamber, and a catalyst sealing member comprising a non-planar pressure sensitive member and disposed within the chamber. The fuel mixture reacts to produce a gas in the presence of a catalyst. The sealing member has a first configuration and a second configuration. A catalyst (48) is contactable by the fuel mixture, when the sealing member is present in the first configuration. The catalyst is not contactable by the fuel mixture, when the sealing member is present in the second configuration.    USE - The apparatus is useful for generating a gas such as hydrogen or oxygen (claimed) to a fuel cell.    ADVANTAGE - The gas-generating apparatus is capable of self-regulating the hydrogen-producing reaction to regulate the flow of fuel, has long shelf life and efficient hydrogen production, and minimizes the fluctuations in pressure of the hydrogen received by the fuel cell.    DETAILED DESCRIPTION - The gas-generating apparatus comprises a reaction chamber (58), a fuel mixture within the chamber, and a catalyst sealing member comprising a non-planar pressure sensitive member and disposed within the chamber. The fuel mixture reacts to produce a gas in the presence of a catalyst. The sealing member has a first configuration and a second configuration. A catalyst (48) is contactable by the fuel mixture, when the sealing member is present in the first configuration. The catalyst is not contactable by the fuel mixture, when the sealing member is present in the second configuration. A pressure in the reaction chamber actuates the non-planar pressure sensitive member to move between the first configuration and the second configuration. The non-planar pressure sensitive member has a cylindrical shape. The catalyst sealing member comprises a flexible chamber (38), a cup disposable against a sealing member, a shaft casing, a ball movable relative to the shaft casing, a catalyst isolating chamber that isolates the catalyst from the fuel mixture in the second configuration, a fuel channel to allow the fuel mixture to contact the catalyst, a corrugated bellows and a pair of cups. The catalyst is disposed within the catalyst sealing member. The catalyst sealing member is open in the first configuration, and is closed in the second configuration. The buoy is open, when a pressure in the flexible chamber is higher than the pressure in the reaction chamber. The buoy is closed, when the pressure in the flexible chamber is lower than the pressure in the reaction chamber. The flexible chamber is elastomeric, and is fluidically connected to the outside of housing (56) such that the pressure in the elastomeric chamber is atmospheric pressure. The pressures in the elastomeric chamber in the catalyst sealing members are different than each other so that the catalyst sealing members are open and close at different pressures inside the reaction chamber. A first spring provides a spring biasing force to balance a reaction chamber force provided by the pressure in the reaction chamber such that when the spring biasing force is greater than the reaction chamber force the catalyst sealing member is present in the first configuration, and when the biasing force is less than the reaction chamber force the catalyst sealing member is present in the second position. The cup is not disposed against the sealing member in the first configuration, and is disposed against the sealing member in the second configuration. The first spring biases the cup through a shaft connected to the cup and a piston connected to the shaft, and acts on the piston. The catalyst is present on the shaft or in the cup, and is attached to the ball or to a shaft connected to the ball. The ball is spaced apart from the shaft casing in the first configuration, and is pushed against the shaft casing in the second configuration. A second spring is provided to move the catalyst sealing member between the first configuration and the second configuration. The fuel mixture comprises two chemical hydrides and water. The reaction chamber comprises a gas-permeable liquid-impermeable composite, which is subjected to a compression pressure within the reaction chamber. A lattice structure is disposed between two gas-permeable membranes. The produced gas flows through one or both of the membranes and into the lattice structure. The fuel channel is formed through the catalyst sealing member. The bladder is expanded and the cups are open, when the catalyst sealing member is present in the first configuration. The bladder is contracted, and the cups are closed, when the catalyst sealing member is present in the second configuration. The gas-generating apparatus further comprises a fuel gage that measures an electrical resistance or the density of the fuel mixture to determine the remaining unreacted fuel.    DESCRIPTION OF DRAWING(S) - The diagram shows a cross-sectional view of a hydrogen-generating apparatus.    Two relief valves (221, 22b)    Flexible chamber (38)    Catalyst sealing mechanisms (40, 42)    Catalyst (48)    Housing (56)    Reaction chamber. (58)