The AAV as it is also known is fitted to the boiler to automatically remove air from the central heating system and the boiler. They work using a float which opens when air is present and closes when it detects no air This ensures air can’t get into the boiler which could cause airlocks and a variety of other problems to the boiler. The auto air vent is normally located on the pump housing ensuring air is removed from the boiler at this point, the point where the water is being circulated and where air bubbles would occur. The pump circulates water around the boiler and also around the central heating system but if the air was present within the pump, the pump would cease to be effective, the boiler would overheat which would cause the boiler to turn off on an overheat fault. Auto-Air Vents are fitted to every boiler and should be checked regularly to ensure they are in good working order.