The Ravenheat automatic air vent is a pressure protection measure for the central heating unit. It works by using a floatation device to release built-up air. As water flows through the heating and cooling system, a float within the automatic air vent opens or closes depending on the water level. If the system contains no air, the float will be pushed to the top and the vent will be closed until the water level drops.

Brand Name	Ravenheat