A hydrogen generator comprising: a housing (12, 14) including an access panel; an initiator assembly disposed in the housing and including one or more contact members; a compressible member having opposing first and second surfaces and within which the one or more contact members are disposed, wherein the compressible member comprises a material comprising one or more of a natural sponge material, an artificial sponge material, a cured elastomer, a cross-linked elastomer, and a vulcanized elastomer; and a fuel unit removably disposed in the housing (12, 14) adjacent the first surface of the compressible member, the fuel unit containing a hydrogen containing material that can release hydrogen gas when heated and an exothermic mixture that can react exothermically upon initiation by energy from the initiator assembly; wherein: when no fuel unit is disposed in the hydrogen generator, the compressible member is uncompressed, and the one or more contact members are at or below the second surface; the access panel is configured to be secured to the housing and comprises a removable portion of the housing or a panel that remains attached to the housing; the access panel is moveable to provide access to the hydrogen generator for insertion and removal of the fuel unit; the housing further comprises an interlock mechanism that prevents movement of the access panel when an internal temperature of the hydrogen generator is above a predetermined level; when a fuel unit is disposed in the hydrogen generator, the compressible member is compressed when the access panel is secured to the housing such that the one or more contact members extend beyond the second surface to make thermal contact with the fuel unit; and the initiator assembly, contact members, and exothermic mixture are configured to conduct energy from the initiator assembly by the one or more contact members to corresponding one or more quantities of the exothermic mixture to initiate an exothermic reaction therein, thereby providing heat for the release of hydrogen gas from the hydrogen containing material. a housing (12, 14) including an access panel; an initiator assembly disposed in the housing and including one or more contact members; a compressible member having opposing first and second surfaces and within which the one or more contact members are disposed, wherein the compressible member comprises a material comprising one or more of a natural sponge material, an artificial sponge material, a cured elastomer, a cross-linked elastomer, and a vulcanized elastomer; and a fuel unit removably disposed in the housing (12, 14) adjacent the first surface of the compressible member, the fuel unit containing a hydrogen containing material that can release hydrogen gas when heated and an exothermic mixture that can react exothermically upon initiation by energy from the initiator assembly; when no fuel unit is disposed in the hydrogen generator, the compressible member is uncompressed, and the one or more contact members are at or below the second surface; the access panel is configured to be secured to the housing and comprises a removable portion of the housing or a panel that remains attached to the housing; the access panel is moveable to provide access to the hydrogen generator for insertion and removal of the fuel unit; the housing further comprises an interlock mechanism that prevents movement of the access panel when an internal temperature of the hydrogen generator is above a predetermined level; when a fuel unit is disposed in the hydrogen generator, the compressible member is compressed when the access panel is secured to the housing such that the one or more contact members extend beyond the second surface to make thermal contact with the fuel unit; and the initiator assembly, contact members, and exothermic mixture are configured to conduct energy from the initiator assembly by the one or more contact members to corresponding one or more quantities of the exothermic mixture to initiate an exothermic reaction therein, thereby providing heat for the release of hydrogen gas from the hydrogen containing material.