Hydrogen purification devices, components thereof, and fuel processors and fuel cell systems containing the same. The hydrogen purification devices include an enclosure, such as a pressure vessel, that contains a separation assembly adapted to receive under pressure a mixed gas stream containing hydrogen gas and to produce a stream that contains pure or at least substantially pure hydrogen gas therefrom. In some embodiments, the enclosure is sealed without gaskets. The separation assembly includes at least one hydrogen-permeable and/or hydrogen-selective membrane, and in some embodiments the hydrogen-selective membrane is permanently and directly secured to the enclosure. In some embodiments, the membrane is welded, diffusion bonded or brazed directly to the enclosure. In some embodiments a portion of the hydrogen-selective membrane forms a portion of the sealed enclosure, and, in some embodiments, an interface is formed from consumed portions of the hydrogen-selective membrane and the enclosure.