Air Outlet Valve

a device for the removal of the air that accumulates in hot-water heating systems. Air outlet valves may be automatically or manually operated. The manually operated outlet valve, which is a cock for periodic air release, is sometimes installed with a trap (tank) where the air accumulates before release. The automatic air outlet valve discharges air as it accumulates by means of floats that open the discharge outlets when the level of the liquid in the device is lowered.