NOVELTY - A purification system purifies a hydrogen stream supplied from a storage tank mounted in a vehicle to produce a purified hydrogen stream for a polymer electrolyte membrane (PEM) fuel cell system utilized within the vehicle. The purification system has a membrane separator, storage tank, pressure regulator, combustor, heat exchangers (I,II) and control valve. The membrane separator utilizes a hydrogen transport membrane material containing metal alloy capable of selectively permeating hydrogen from the hydrogen stream at an elevated membrane operational temperature.    USE - Purification system is used for purifying hydrogen stream supplied from storage tank mounted in vehicle for producing purified hydrogen stream (claimed) for polymer electrolyte membrane fuel cell system used in vehicle.    ADVANTAGE - The purification system efficiently purifies the hydrogen stream.    DETAILED DESCRIPTION - A purification system purifies a hydrogen stream supplied from a storage tank mounted in a vehicle to produce a purified hydrogen stream for a polymer electrolyte membrane (PEM) fuel cell system utilized within the vehicle. The purification system has a membrane separator, storage tank, pressure regulator, combustor, heat exchangers (I,II) and control valve. The membrane separator utilizes a hydrogen transport membrane material containing a metal or metal alloy capable of selectively permeating hydrogen from the hydrogen stream at an elevated membrane operational temperature, thereby to produce purified hydrogen permeate stream and a retentate stream comprising impurities contained in the hydrogen stream. The membrane separator is in flow communication with the storage tank to receive the hydrogen stream and in flow communication with the PEM fuel cell system to form the purified hydrogen stream from the purified hydrogen permeate stream produced in the membrane separator. The pressure regulator is located between the storage tank and the membrane separator and configured to control pressure of the hydrogen stream to a membrane separator operational pressure. The combustor is connected to the membrane separator and configured to combust the retentate stream to produce a heated exhaust stream. The heat exchangers (I,II) are located between the pressure regulator and the membrane separator to transfer heat from the purified hydrogen permeate stream and from the heated exhaust stream to the hydrogen stream to heat the hydrogen stream and therefore the hydrogen transport membrane material to the elevated membrane operational temperature. The heat exchangers (I,II) are connected to the membrane separator and the combustor, respectively, such that the purified hydrogen permeate stream indirectly exchanges heat to the hydrogen stream and the heated exhaust stream indirectly exchanges further heat to the hydrogen stream. The control valve is interposed between the heat exchanger (I) and the PEM fuel cell, and configured to control pressure of the purified hydrogen stream to a PEM fuel cell operational pressure. The combustor has an oxidation catalyst to facilitate the combustion of the retentate stream. The metal is palladium or the metal alloy contains palladium.