Vents trace amounts of gas continuously, as they occur and accumulate in the valve. Recommended for applications prone to outgassing, ozone processes, etc. This is a normally open valve -- vents in or out -- increasing liquid pressure forces air/gas out. Rising liquid lifts a natural polypropylene float, which acts on an armature and seal to close the valve bubble tight. When air or gas accumulates again, the float drops and the valve reopens. Liquid pressure forces the gas to be expelled, and then re-closes the valve. The process repeats over and over, automatically, as gas accumulates. The valve has a very small orifice and is designed for trace amounts of gas. To expel large volumes of air such as at system start-up, see Series ARV above. If your application requires expulsion of a large amount of air, as well as periodic venting of smaller amounts, you may require both the Series ARV and Series DGV.