NOVELTY - A hydrogen generator (10) comprises housing (12); liquid reservoir in housing and comprising liquid reactant container, made of liquid impermeable material, and containing liquid comprising first reactant; reaction area (22) in housing and comprising reaction container (20) made of liquid impermeable material; byproduct containment area (26) comprising flexible byproduct container (16) made of hydrogen permeable, liquid impermeable material through which solids and liquids cannot pass but through which hydrogen gas can pass; hydrogen containment area (28); and hydrogen outlet (38).    USE - As hydrogen generator in fuel cell system (claimed), where fuel cell systems are used as power sources for portable electronic applications.    ADVANTAGE - The hydrogen generator is capable of supplying hydrogen gas to a fuel cell stack with improved effectiveness and reliability of the separation of hydrogen gas from liquids and solids within the hydrogen generator. The hydrogen generator is less susceptible to internal restrictions or blockages that can impede the separation and release of the hydrogen gas. The hydrogen generator has excellent reliability, safety, volume efficiency and a simple design that is easily manufactured at a low cost.    DETAILED DESCRIPTION - A hydrogen generator (10) comprises housing (12); a liquid reservoir within the housing and comprising a liquid reactant container, made of a liquid impermeable material, and containing a liquid comprising a first reactant; a reaction area (22) within the housing and comprising a reaction container (20), made of a liquid impermeable material, and within which the first reactant reacts to produce hydrogen gas and byproducts; a byproduct containment area (26) within the housing and comprising a flexible byproduct container (16), made of a hydrogen permeable, liquid impermeable material through which solids and liquids cannot pass but through which hydrogen gas can pass; a hydrogen containment area (28) within the housing and comprising a flexible hydrogen gas container, made of a hydrogen impermeable material, and configured to contain hydrogen gas from the byproduct containment area; and a hydrogen outlet (38) from the hydrogen containment area through the housing, where the byproduct containment area is in a volume exchanging relationship with at least one of the liquid reservoir and the reaction area. A catalyst configured to catalyze the reaction of the first reactant is initially contained within the reaction area. A second reactant is initially contained within the reaction area. The hydrogen generator comprises an accelerant that is capable of providing an increased rate of reaction. An INDEPENDENT CLAIM is included for a fuel cell system comprising a fuel cell stack and the hydrogen generator. The hydrogen generator is removable from the rest of the fuel cell system.    DESCRIPTION OF DRAWING(S) - The figure shows schematic cross-sectional view of a hydrogen gas generator in an initial state.    Hydrogen generator (10)    Housing (12)    Byproduct container (16)    Flexible container (18)    Reaction container (20)    Reaction area (22)    Liquid reservoir (24)    Byproduct containment area (26)    Hydrogen containment area (28)    Liquid reactant outlet (30)    Liquid reactant inlet (32)    Liquid disperser (34)    Reaction area outlet (36)    Hydrogen gas outlet (38)