A gas purging valve is operative to be connected to piping in a Fire Protection System (FPS) and to bleed gas at a predetermined rate. The valve includes an inlet in gas flow relationship with the FPS piping and a central passage in gas flow relationship with the inlet. The valve also includes a calibrated orifice removeably disposed in the central passage, in gas flow relationship with the passage and operative to allow a maximum predetermined gas flow rate therethrough. The valve further includes an outlet in gas flow relationship with the calibrated orifice. A ball is disposed upstream of the central passage. The ball is operative to allow gas flow through the gas purging valve but operative to impede the flow of water through the gas purging valve.