Also known as Air & Vacuum valves discharge large quantities of air from non-pressurized pipes and are used mainly when filling a line. Air & vacuum valves also make it possible to admit large quantities of air when lines are drained and when the pressure drops suddenly. Air & vacuum valves are also known as large orifice air valves, vacuum breakers, low-pressure air valves and air-relief valves.

Also known as air release valves continuously release relatively small quantities of air from a pressurized line. The automatic air release valve is also known as a small orifice air valve and as a pressure air valve.

Combination air valves fulfill the tasks required of both types of valve: air & vacuum (kinetic) valve and air release (automatic) valve. In other words - they discharge or intake large volumes of air when filling or emptying a system and continuously release small volumes air when the line is pressurized. Combination air valves are also known as double orifice air valves.

The D-060 HF NS series Combination Non Slam Air Valve is a surge-dampening, slam-preventing, 3-stage combination air valve. The air valve provides high capacity vacuum protection and, at the same time, efficient surge suppression. At sudden drainage and/or water column separation (sudden pump trips or valve closure, for instance), the air & vacuum orifice admits air at high flow rates, thus preventing vacuum. As the water column and/or pressure wave returns, large volumes of air are discharged at high velocities, raising the non-slam disc, partially closing the air & vacuum orifice and allowing air to exhaust slowly through the smaller orifice of the non-slam disc. This slowly exhausting air pocket dampens the slam of the returning water column, thus suppressing the pressure surge. As the water flow arrives at a much slower rate, dampened by the slower air discharge, it buoys up the main float, gently closing the air & vacuum component of the air valve.