Mechanism of diving regulators

The mechanism of diving regulators is the arrangement of components and function of gas pressure regulators used in the systems which supply breathing gases for underwater diving. Both free-flow and demand regulators use mechanical feedback of the downstream pressure to control the opening of a valve which controls gas flow from the upstream, high-pressure side, to the downstream, low-pressure side of each stage.^[1] Flow capacity must be sufficient to allow the downstream pressure to be maintained at maximum demand, and sensitivity must be appropriate to deliver maximum required flow rate with a small variation in downstream pressure, and for a large variation in supply pressure, without instability of flow. Open circuit scuba regulators must also deliver against a variable ambient pressure. They must be robust and reliable, as they are life-support equipment which must function in the relatively hostile seawater environment, and the human interface must be comfortable over periods of several hours.

Diving regulators use mechanically operated valves.^[1] In most cases there is ambient pressure feedback to both first and second stage, except where this is avoided to allow constant mass flow through an orifice in a rebreather, which requires a constant absolute upstream pressure. Back-pressure regulators are used in gas reclaim systems to conserve expensive helium based breathing gases in surface-supplied diving, and to control the safe exhaust of exhaled gas from built-in breathing systems in hyperbaric chambers.

The parts of a regulator are described here as the major functional groups in downstream order following the gas flow from the cylinder to its final use. Details may vary considerably between manufacturers and models.