[abstract] SCUBA REGULATOR PERFORMANCE FOR UNDER-ICE SCIENTIFIC DIVING OPERATIONS

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[abstract] SCUBA REGULATOR PERFORMANCE FOR UNDER-ICE SCIENTIFIC DIVING OPERATIONS

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Title: [abstract] SCUBA REGULATOR PERFORMANCE FOR UNDER-ICE SCIENTIFIC DIVING OPERATIONS
Author: Lang, M; Clarke, J
Abstract: BACKGROUND: Single-hose scuba regulators dived in very cold water have a probability of experiencing first- or second-stage malfunction yielding complete occlusion of air flow or massive free flow that rapidly expends a diver's air supply, both conditions referred to as regulator "freeze-up". Principal factors contributing to ice crystallization in the regulator second stage include manufacturer's design, materials, and quality control, exhalant breath of diver, adiabatic gas expansion, mass flow, time, and temperature. MATERIALS AND METHODS: 11 divers (mean height 180.1 cm, mean weight 84.6 kg) logged a total of 133 dives in -1.86 C sea water under 6-m thick Antarctic fast ice. Dive profiles had an average depth of 38 msw and dive time of 29 min, including a mandatory 3 min safety stop at 6 msw. Twenty-seven commercially available, unmodified regulator units from 9 different manufacturers underwent standardized pre-dive regulator care and were randomly assigned to divers. Depths and times of onset of second-stage regulator free-flow were recorded. RESULTS: In 133 dives, there were 28 free flows. The free flows were not evenly distributed across the regulator brands. The regulators classified for the purpose of the test as "better" suffered only 5 free-flows out of 77 exposures (6% combined incidence), and the others suffered 23 out of 56 exposures (41% free-flow incidence). Testing on three regulators was aborted when free flow incidence reached 50%. Differences between regulator free-flow incidences were tested by the Chi-square test. The pooled incidences for the four best performing regulators were compared to the five remaining regulators. The differences between the groupings was significant at P<0.001. CONCLUSION: Regulator freeze-up is a probabilistic event; even the best regulators can fail under polar conditions. Combined laboratory and field-testing, proper pre-dive regulator care, depth-dependent gas density control, breathing rate, and diver experience can influence freeze-up incidence.
Description: Abstract of the Undersea and Hyperbaric Medical Society, Inc. Annual Scientific Meeting, Las Vegas, Nevada, USA. (http://www.uhms.org)
URI: http://archive.rubicon-foundation.org/9175
Date: 2009

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  • UHMS Meeting Abstracts
    This is a collection of the published abstracts from the Undersea and Hyperbaric Medical Society (UHMS) annual meetings.

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