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. Ansti Test Systems developed a turnkey system that measures the inhalation and exhalation effort in using a regulator. Publishing results of the performance of regulators in the ANSTI test machine has resulted in performance improvements.
In the European Union the standard EN250:2000 <Respiratory equipment. Open-circuit self-contained compressed air diving apparatus. Requirements, testing, marking> defines minimum performance standards for "Open-circuit self-contained compressed air diving apparatus".
The standard contains limits on inhalation and exhalation pressures and overall work of breathing. It specifies the following, under test conditions of a breathing rate of 62.5 litres (2.2 cu ft) per minute and an ambient pressure of 6 bars (600 kPa):
- Work of breathing: <3.0 joules per litre
- Peak respiratory pressure: ±25 mbar (±2.5 kPa) (inhalation or exhalation)
- Inhalation work of breathing: <0.3 joule per litre
- 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.
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- "Demand Regulator Test Station". Ansti Test Systems Ltd. 2003-06-19. Retrieved 2009-09-14.
- "The ANSTI Machine: Evaluating A Regulator's Breathing Characteristics - Scuba Diving Magazine".
- ISBN 0-580-35713-9 British Standards Institution
- "HSE publishes research on performance of 'octopus' regulators for scuba diving".
- Middleton, JR (1980). "Evaluation of Commercially Available Open Circuit Scuba Regulators.". US Naval Experimental Diving Unit Technical Report. NEDU-2-80. Retrieved 2008-06-12.
- Morson, PD (1987). "Evaluation of Commercially Available Open Circuit Scuba Regulators.". US Naval Experimental Diving Unit Technical Report. NEDU-8-87. Retrieved 2008-06-12.
- Warkander, DE (2007). "Comprehensive Performance Limits for Divers' Underwater Breathing Gear: Consequences of Adopting Diver-Focused Limits.". US Naval Experimental Diving Unit Technical Report. NEDU-TR-07-02. Retrieved 2008-06-12.