A passive dual modulating regulator with relative differential venting (regulator) for use with a contained hydrogen generation system (system) comprises a housing, a first piston valve, a second piston valve, and a third piston valve. The regulator defines a hydrogen fluid path in fluid communication with a hydrogen-side of the system, an exterior hydrogen storage vessel, and an exterior of the system. The regulator also defines an oxygen fluid path in fluid communication with the oxygen-side of the system, an exterior oxygen storage vessel, and an exterior of the system. The regulator regulates pressure imbalances between the oxygen-side of the system and the hydrogen-side of the system, and vents oxygen and hydrogen to the exterior of the system to allow collection of both hydrogen and oxygen and avoid rupture of a proton-exchange membrane of the system.