The Xylem-Hoffman Specialty 401475 Water & Steam Vent Valve (1/8" NPT, 50 PSI) is a precision air vent designed for steam and hydronic HVAC systems. It automatically releases trapped air from radiators, convectors, unit heaters, and steam mains to improve heat distribution and system efficiency. The valve operates by opening to discharge air during startup and closing tightly when ste... https://www.partshnc.com/50psi-wtrsteam-vent-18-508