The Worcester Bosch automatic air vent is a pressure safety measure for the central heating unit. They work by using a floatation device to release built-up air. As water flows through the heating or cooling system, a float within the automatic air vent opens or closes depending on the water level. If the system contains only water, the float will be pushed to the top and the vent will be closed until the water level drops.

Brand Name	Worcester Bosch