Editing Scuba set (section)

=====Single-hose regulator=====
{{main|Diving regulator#Single hose two-stage open-circuit demand regulators}}
[[Image:Aqua lung.jpg|thumbnail|A single-hose regulator with 2nd stage, gauges, BC attachment, and dry suit hose mounted on a cylinder]]
Most modern open-circuit scuba sets have a [[diving regulator]] consisting of a first-stage pressure-reducing valve connected to the [[diving cylinder]]'s output valve or manifold. This regulator reduces the pressure from the cylinder, which may be up to {{convert|300|bar|psi}}, to a lower pressure, generally between about 9 and 11&nbsp;bar above the ambient pressure. A low-pressure hose links this with the second-stage regulator, or "demand valve", which is mounted on the mouthpiece. Exhalation occurs through a rubber one-way mushroom valve in the chamber of the demand valve, directly into the water quite close to the diver's mouth. Some early single hose scuba sets used full-face masks instead of a mouthpiece, such as those made by Desco<ref name=Desco /> and Scott Aviation<ref name="Scott Aviation" /> (who continue to make breathing units of this configuration for use by [[firefighters]]).

Modern regulators typically feature high-pressure ports for pressure sensors of dive-computers and submersible pressure gauges, and additional low-pressure ports for hoses for inflation of dry suits and BC devices.<ref name="Harlow" />