Self Contained Underwater Breathing Apparatus (SCUBA) often use an ‘Octopus’ system as an alternative air supply. QinetiQ at Alverstoke were contracted by the Health and Safety Executive (HSE) (Contract D5008) to conduct a review and breathing performance test of ‘Octopus’ systems. It was shown that SCUBA single demand valve systems capable of meeting the breathing performance requirements of BS EN 250, cannot be relied upon to meet the same requirements when used as part of an ‘Octopus’ system. Reduced breathing performance of ‘Octopus’ systems (when compared to single valve systems) was found to be a result of the use of low performance first stage regulators, second stage demand valves of different and poor performance and breathing in phase as opposed to out of phase. Recommendations on the use of ‘Octopus’ systems are presented. Appropriate test procedures and acceptance criteria should be identified for ‘Octopus’ systems, and proposed for the next revision of BS EN 250.
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