空气阀和通风口流入防止器组件的目的是允许通过饮用水分配系统中的空气阀和通风口释放和进入大量空气，但当空气阀出口被淹没或成为恶意篡改的目标时，防止污染水进入。总成由一级和二级腔室组成。每个腔室包含一个独立的浮子操作的闭合构件。主室是下室。辅助或上部腔室是冗余的，如果主腔室未能关闭，则会关闭。 可接受达到本标准性能要求的其他配置。

The purpose of air valve and vent inflow preventer assemblies is to allow the release and admission of high volumes of air through air valves and air vents in potable water distribution systems, but prevent the entry of contaminated water when the air valve outlet becomes submerged from flooding or is the target of malicious tampering.Assemblies consist of a primary and secondary chamber. Each chamber contains an independent float-operated closure member. The primary chamber is the lower chamber. The secondary or upper chamber is redundant and will close in the event that the primary chamber fails to close. Other configurations achieving the performance requirements of this standard are acceptable.