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Assessment of Manual Operations and Emergency Procedures for Closed Circuit Rebreathers

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Assessment of Manual Operations and Emergency Procedures for Closed Circuit Rebreathers Health and Safety Executive Assessment of manual operations and emergency procedures for closed circuit rebreathers Prepared by Cranfield University for the Health and Safety Executive 2011 RR871 Research Report Health and Safety Executive Assessment of manual operations and emergency procedures for closed circuit rebreathers Dr Sarah Fletcher Cranfield University Cranfield Bedfordshire MK43 0AL Closed Circuit Re-breather (CCR) diving has become increasingly popular as more sophisticated units enable diving for longer and at greater depths. CCR diving is much more complex than traditional open circuit diving in many ways and there is an increased potential for problems and diver errors to emerge. However, formal research examining CCR safety has been rare. To address this, the UK Health and Safety Executive commissioned the Department of Systems Engineering and Human Factors at Cranfield University to conduct a scoping study into the human factors issues relevant to CCR diving apparatus. The scoping study was designed to explore five principal subject areas: accident / incident analysis, unit assembly / disassembly, normal / non-normal diving operations, training needs analysis, interface and display. This scoping study has approached this with a series of studies each addressing separate issues that are relevant to the principal subject areas. These studies can be seen as potentially stand alone, each with its own objectives, method and results. These studies comprise; Accident / Incident Analysis; Human Error Potential Analysis: Assembly and Disassembly; Human Error Potential Analysis of Diving Operations; Training Needs Analysis; Interface and Display Recommendations and Human Error Potential in Non-Normal Operations. 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 authors alone and do not necessarily reflect HSE policy. HSE Books © Crown copyright 2011 First published 2011 You may reuse this information (not including logos) free of charge in any format or medium, under the terms of the Open Government Licence. To view the licence visit www.nationalarchives.gov.uk/doc/open-government­ licence/, write to the Information Policy Team, The National Archives, Kew, London TW9 4DU, or email [email protected]. Some images and illustrations may not be owned by the Crown so cannot be reproduced without permission of the copyright owner. Enquiries should be sent to [email protected]. ii ACKNOWLEDGEMENTS For their considerable assistance with the various components of this project we would like to thank the following: AP Diving TDI • Martin Parker • Stephen Philips (UK) • Nicola Finn • Sean Harrison (US) • Mike Etheredge VR Technology BSAC • Kevin Gurr • Brian Cumming HM Coroners: • Gavin Anthony • W. Armstrong (Greater Norfolk HSE District) • Richard Martins • T. Brown (North Northumberland) • Nicholas Bailey • P. McNab (Northern Ireland) • Damien Walker • S.S. Payne (Bournemouth, Poole • Steve Field and Eastern Dorset District) InnerSpace Systems • D. Pritchard Jones (North West Wales District) • Leon Scamahorn • M.C. Johnstone (Western District • Jerry Watley of Dorset) iii iv EXECUTIVE SUMMARY Closed circuit diving rebreather (CCR) technology has progressed significantly over recent years enabling divers to dive deeper and for longer. This type of equipment, which traditionally was used primarily in the military field, is also now used at work in commercial and recreational diving as well as by leisure divers. CCR diving is much more complex than traditional open circuit diving in many ways and there is an increased potential for problems and diver errors to emerge. However, formal research examining CCR safety has been rare. To address the well-documented paucity of empirical research and knowledge in this area the UK Health and Safety Executive commissioned the Department of Systems Engineering and Human Factors at Cranfield University to conduct a unique scoping study investigation of CCR diving apparatus. The scoping study was designed to explore five principal subject areas in separate sub-projects: accident / incident analysis, unit assembly / disassembly, normal / non-normal diving operations, training needs analysis, interface and display. The focus and breadth of the sub-projects had to be expanded in some places to accommodate unexpected developments and discoveries that emerged as the work progressed. Nonetheless, the overall remit of ‘scoping’ research, to identify key areas in need of further investigation, was maintained throughout. This scoping study has comprised a series of studies addressing separate issues, each headed by individual members of the project team. After the first introductory chapter, chapters 2-7 of this report will each set out one of the studies. These studies can therefore be seen as a potentially stand alone, each with its own objectives, method and results. Chapter 2 Accident / Incident Analysis; Dr Sarah Fletcher This first study was designed to analyse accident / incident data. As little reliable data on recreational CCR accidents and incidents is available the study reviewed relevant literature, sought UK coroner reports and incorporated a set of interviews to gather self-reports from current CCR divers. Main findings reveal current deficiencies in: synergy and communication between key CCR organisations, procedure and regulatory oversight over diver training and accident investigation, general awareness of diver behaviours which could be highly advantageous for the development of behavioural based training components. Chapter 3 Human Error Potential Analysis: Assembly and Disassembly; Dr Steve Jarvis In this study the human error potential for CCR unit assembly and disassembly tasks was analysed using the Systematic Human Error and Prediction Approach (SHERPA) methodology. The study identified eight task errors which could become more likely and safety critical in disorganised circumstances. These errors lead to various recommendations for design modifications to reduce possibilities of inaccurate assembly more rigorous storage and disposal procedures to be educated and reinforced. Mandating the use of simplified checklists is also v recommended, along with supplementary education so that divers fully understand why each checklist point task is important. Chapter 4 Human Error Potential Analysis of Diving Operations; Jonathon Pike This study also applied the SHERPA methodology to task analyses of ‘normal’ diving operations, drawing upon Standard Operating Procedures (SOPs). Findings comprise a long list of issues and recommendations including: building the check sequence into controller software, incorporating a degree of human error education into diver training, greater human factors in unit design, making Human Factors analysis of units part of EN standards, adding CO2 measurement systems directly downstream from the scrubber to warn of rising levels indicative of breakthrough, and further investigation of personal unit adaptations and the potential remedial impact of bespoke training. Chapter 5 Training Needs Analysis; Dr John Huddlestone The CCR Training Needs Analysis (TNA) study was conducted using analyses produced in the previous chapter / study, and a set of semi-structured interviews with representatives from manufacturing and training organisations. A broad set of recommendations for training was generated, these include: Advanced Nitrox training as standard, trainee minimum entry and instructor currency requirements, optimising course length and content incorporating Human Factors theory, specifying attitude goals, mandating UK courses are delivered by unit manufacturers with more emergency situation training and manuals with checklists for emergency situations, using alternative assessment models e.g. independent assessors or graduated learning progression, recurrent training and feedback mechanisms. Chapter 6 Interface and Display Recommendations; Jonathon Pike This individual study set out to assess best practice and identify key design principles which should be applied to the design of CCR interfaces and displays. This analysis was conducted using the FAA Human Factors Design Standard (FAA, 2003) as the main reference and guide. The study’s findings primarily highlight the need for review of EN standards to cover specification of interfaces and controls, plus further research to identify and develop design guidance and, once again, to gain better understanding of personal adaptations to units. Chapter 7 Human Error Potential in Non-Normal Operations; Dr Sarah Fletcher This study undertook analysis and evaluation of ‘non-normal’ or emergency CCR diving procedures. The SHERPA method was partially used but the complexity and uniqueness of emergent situations made prediction very difficult. Key findings and suggestions were produced, however, including: the feasibility of designing units to reduce or eliminate the possibility of making adaptations, develop training that better addresses emergency procedures and drill practice including unit variations / adaptations, update standards to cover emergency procedures and personal adaptations, conduct further work to examine individual differences. vi CONTENTS Acknowledgements iii Executive Summary v Glossary of Terms xi 1. Introduction 1 1.1 Overview 1 1.2 Background 1 1.3 Structure of Work 2 1.4 Structure of report 3 2. Accident / Incident Analysis 4 2.1 Introduction 4 2.2
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