Reduced pressure vent for heating, ventilation and air conditioning systems

A pressure relief valve includes a housing configured for mounting into a conduit opening of a conduit, and a diffuser mounted into the housing and movable along a valve axis between a closed position and an open position. The diffuser includes a tubular diffuser body having an inlet opening at a first end, a diffuser cap at a second end of the tubular diffuser body to close the tubular diffuser body at the second end, and one or more outlet openings between the inlet opening and the diffuser cap. The biasing element biases the position of the diffuser toward the closed position. When the airflow pressure in the conduit exceeds a threshold, the airflow urges the diffuser toward the open position, allowing the airflow to exit the relief valve at the one or more outlet openings. 一种减压阀，包括配置成用于安装到导管的导管开口中的壳体，以及安装到壳体中并可沿着阀轴线在关闭位置和打开位置之间移动的扩散器。扩散器包括在第一端具有入口开口的管状扩散器主体、位于管状扩散器主体的第二端以在第二端封闭管状扩散器主体的扩散器帽以及位于入口开口和扩散器帽之间的一个或多个出口开口。偏压元件将扩散器的位置朝向关闭位置偏压。当导管中的气流压力超过阈值时，气流将扩散器推向打开位置，从而允许气流在一个或多个出口开口处离开减压阀。