Breathing performance of regulators

A diving regulator is a device that reduces the high pressure in a diving cylinder to the same pressure as the scuba diver's surroundings. The breathing performance of regulators is a factor in choosing a suitable regulator for the type of diving to be undertaken, as it indicates the ability of a regulator to meet the demands placed on it at depth and under high breathing loads. It is desirable that breathing from a regulator requires low effort even when supplying large amounts of air. It is also recommended that it breathe smoothly without any sudden changes in resistance while inhaling or exhaling. Although these factors may be judged subjectively, it is convenient to have a standard by which the many different types and manufactures of regulators may be compared.

Various breathing machines have been developed and used for assessment of breathing apparatus performance. [cite journal |last=Reimers |first=SD |title=Performance Characteristics and Basic Design Features of a Breathing Machine for Use to Depths of up to 3000 Feet of Sea Water. |journal=US Naval Experimental Diving Unit Technical Report |volume=NEDU-20-73 |date=1973 |url=http://archive.rubicon-foundation.org/4100 |accessdate=2008-06-12 ] ANSTI has developed a testing machine that measures the inhalation and exhalation effort in using a regulator; publishing results [cite web |url=http://www.scubadiving.com/gear/regulators/bonus_2007_reg_test/ansti_machine |title=The ANSTI Machine: Evaluating A Regulator's Breathing Characteristics - Scuba Diving Magazine] of the performance of regulators in the ANSTI test machine has resulted in big performance improvements.

EU Standard

In the European Union the standard EN250:2000 "" defines minimum performance standards for "Open-circuit self-contained compressed air diving apparatus". [ISBN 058035713 9 British Standards Institution]

The standard contains limits on inhalation and exhalation pressures and overall work of breathing.

The following are under test conditions of a breathing rate of 62.5 liters per minute and an ambient pressure of 6 bar (600 kPa):

*Work of breathing: <3.0 joules per liter
*Peak respiratory pressure: ±25 mbar (±2.5 kPa) (inhalation or exhalation)
*Inhalation work of breathing: <0.3 joule per liter
*Pressure spikes with no measurable positive work of breathing: <10 mbar (1 kPa)
*Pressure spikes with measurable positive work of breathing: <5 mbar (0.5 kPa)

Although a regulator meeting the above limits will supply sufficient air where the first stage feeds a single second stage, it is not necessarily capable of supplying sufficient air in all circumstances when a single first stage feeds two second stages simultaneously. [cite web|url=http://www.hse.gov.uk/press/2005/e05057.htm |title=HSE publishes research on performance of 'octopus' regulators for scuba diving]

US Military

In the United States Military, scuba regulators must adhere to performance specifications as outlined by the Mil-R-24169B which was based on equipment performance until recently. [cite journal |last=Middleton |first=JR |title=Evaluation of Commercially Available Open Circuit Scuba Regulators. |journal=US Naval Experimental Diving Unit Technical Report |volume=NEDU-2-80 |date=1980 |url=http://archive.rubicon-foundation.org/3375 |accessdate=2008-06-12 ] [cite journal |last=Morson |first=PD |title=Evaluation of Commercially Available Open Circuit Scuba Regulators. |journal=US Naval Experimental Diving Unit Technical Report |volume=NEDU-8-87 |date=1987 |url=http://archive.rubicon-foundation.org/4259 |accessdate=2008-06-12 ] [cite journal |last=Warkander |first=DE |title=Comprehensive Performance Limits for Divers' Underwater Breathing Gear: Consequences of Adopting Diver-Focused Limits. |journal=US Naval Experimental Diving Unit Technical Report |volume=NEDU-TR-07-02 |date=2007 |url=http://archive.rubicon-foundation.org/4984 |accessdate=2008-06-12 ]

References