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RR492 - Standard unmanned testing procedures for open-circuit ‘Octopus’ systems

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 (Contract 6253) to identify appropriate simple (single breathing machine) test procedures for ‘Octopus’ systems. A single breathing machine, in conjunction with a constant flow from the first stage regulator, was able to represent the breathing performance of an ‘Octopus’ SCUBA system obtained by dual in-phase breathing machines. A test procedure is proposed that uses a constant flow equivalent to the root mean square of the peak flow (ie ventilation rate * 0.707 * p * pressure (bar)). The proposed procedure should be considered for inclusion in future diving apparatus standards including the next revision of BS EN 250. Tests re-confirmed the recommendation that ‘Octopus’ systems should be based on high performance (possibly higher cost) first stage regulators.

This report and the work it describes were funded by the Health and Safety Executive (HSE). Its contents, including any opinions and/or conclusions expressed, are those of the author alone and do not necessarily reflect HSE policy.

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Updated 2010-03-19