This document specifies the characteristics and the requirements of air gap with non-circular overflow (unrestricted) Family A, Type B for nominal flow velocity not exceeding 3 m/s. Air gaps are devices for protection of potable water in water installations from pollution by backflow. This document applies to air gaps in factory-assembled products and to constructed air gaps in situ and defines requirements and methods to verify and ensure compliance with this document during normal working use. The fluid in the receiving vessel is assumed to have similar properties to the water supply. Where this is not the case, additional care or tests could be required to verify the efficacy of the solution in practical use.