Gas control valve

A system for containing leakage along a pintle shaft (22') in a pintle-type gas control valve, such as an exhaust gas recirculation valve for an internal combustion engine or a reformate diverter valve for a fuel cell, comprising a novel seal element and means for sealing the element to the valve's pintle shaft bearing and to an interrupted pintle shaft. The system comprises two elements: a positive vapor block in the form of an elastomeric boot or folded diaphragm (56) disposed across the pintle interruption, and a pintle shaft bearing (26') disposable in the valve's body and sealingly secured to the boot or diaphragm (56). The system may include a coil spring (50') disposed in compression within the boot or diaphragm (56).