A gas distribution system, comprising: a hydrogen-producing region configured to produce a hydrogen-containing reformate gas stream containing hydrogen gas as a majority component; a heating assembly configured to combust a fuel stream to produce a heated exhaust stream to heat the hydrogen-producing region; a separation region configured to receive the reformate gas stream and to separate the reformate gas stream into at least a product hydrogen stream, which contains a greater concentration of hydrogen gas than the reformate gas stream, and a byproduct stream, which has a reduced concentration of hydrogen gas than the reformate gas stream; a first fluid conduit establishing fluid communication for the reformate gas stream between the hydrogen-producing region and the separation region; a second fluid conduit establishing fluid communication for the byproduct stream between the separation region and the heating assembly; and an automatic temperature-responsive valve assembly configured reversibly to alter a gas flow of at least one of the product hydrogen stream and the byproduct stream responsive to the temperature of the valve assembly; wherein the valve assembly further includes a restrictive assembly with at least an obstructive member having a first coefficient of thermal expansion and a support member having a second coefficient of thermal expansion, and wherein the valve assembly is configured such that a difference between the first and second coefficients of thermal expansion determines the manner in which the valve assembly alters the gas flow of at least one of the product hydrogen stream and the byproduct stream through a passage. a hydrogen-producing region configured to produce a hydrogen-containing reformate gas stream containing hydrogen gas as a majority component; a heating assembly configured to combust a fuel stream to produce a heated exhaust stream to heat the hydrogen-producing region; a separation region configured to receive the reformate gas stream and to separate the reformate gas stream into at least a product hydrogen stream, which contains a greater concentration of hydrogen gas than the reformate gas stream, and a byproduct stream, which has a reduced concentration of hydrogen gas than the reformate gas stream; a first fluid conduit establishing fluid communication for the reformate gas stream between the hydrogen-producing region and the separation region; a second fluid conduit establishing fluid communication for the byproduct stream between the separation region and the heating assembly; and an automatic temperature-responsive valve assembly configured reversibly to alter a gas flow of at least one of the product hydrogen stream and the byproduct stream responsive to the temperature of the valve assembly; wherein the valve assembly further includes a restrictive assembly with at least an obstructive member having a first coefficient of thermal expansion and a support member having a second coefficient of thermal expansion, and wherein the valve assembly is configured such that a difference between the first and second coefficients of thermal expansion determines the manner in which the valve assembly alters the gas flow of at least one of the product hydrogen stream and the byproduct stream through a passage.