A rapid, efficient and foolproof Purge Valve for 100% replacement of air in reaction vessels with any desired gas (N2, H2, AR, Cl2, etc.). No mercury used, no reducing valve needed on gas source, no high vacuum source necessary. No need to watch manometers, hand control gas flow, or install warning systems to prevent accidents. Expensive gases are conserved because once purging is complete, the flow can be cut almost to zero. Available with tube connection to system or #15 O-ring joint connection.