The HERZ 1/2" Automatic Air Vent is used to vent air from heating installations. The air vent must be positioned close to the heating device (boiler, combi boiler, heat pump etc.) or at the highest points of the installation. Installations must be made in such a way that it is not possible for air bubbles to be trapped in a certain section of the installation. Before use, turn the polypropylene cap on the cover 2 to 3 turns. In the event of uncontrolled medium leakage, tighten the cap. We always recommend using a backflow preventer for ease of service and replacement of the air vent. The air vent has a STOP function (check valve) that prevents ambient air from entering the heating installation.