Editing Scuba set (section)

===Second stage isolation valve===
A manually operated shut-off valve may be fitted between the low-pressure hose and the second stage, which can be used to isolate the second stage in a free-flow, or at any time when it is necessary. When this is fitted, an over-pressure relief valve us necessary on the first stage. Low profile valves operated by sliding an axial sleeve are available for this purpose and are less likely to snag than a quarter-turn ball valve, and are faster to operate than a screw-down valve, such as is standard on diving helmets for bailout.<ref name="Zeagle" />