Fresh Air in Dark Places First edition published 2010 ISBN: 978 1 905331 89 5 © Witherby Seamanship International Ltd, 2010 British Library Cataloguing in Publication Data A catalogue record for this book is available from the British Library. Notice of Terms of use All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, without the prior permission of the publishers. While the advice given in this book has been developed using the best information currently available, it is intended purely as guidance to be used at the user’s own risk. Witherby Seamanship International Ltd accepts no responsibility for the accuracy of any information or advice given in the document or any omission from the document or for any consequence whatsoever resulting directly or indirectly from compliance with or adoption of guidance contained in the document even if caused by failure to exercise reasonable care. This publication has been prepared to deal with the subject of Fresh Air in Dark Spaces. This should not, however, be taken to mean that this publication deals comprehensively with all of the issues that will need to be addressed or even, where a particular issue is addressed, that this publication sets out the only definitive view for all situations. Printed and bound in Great Britain by Bell & Bain Ltd, Glasgow Published in 2010 by: Witherby Seamanship International Ltd 4 Dunlop Square, Livingston Edinburgh, EH54 8SB Scotland, UK Tel No: +44(0)1506 463 227 Fax No: +44(0)1506 468 999 Email: [email protected] www.witherbyseamanship.com Fresh Air in Dark Places by Olsen & Olsen v Contents Authors’ Introduction vii Foreword viii Introduction ix The Death Toll must be Cut x 1 A Straightforward Approach 1 1.1 Systematic Approach to Safety 1 1.2 What is ‘Fresh Air’? 2 1.3 Weight of Air and Different Gases – an Introduction to Molecular Mass 3 1.3.1 Methane 5 1.3.2 Vapours Lighter than Methane 7 1.4 The Hazard of Invisible Gases 7 1.5 Temperature and Pressure Variation 9 2 What is so Special about Fresh Air? 11 2.1 Oxygen 11 2.2 Spaces with less than 20.9% Oxygen 12 2.3 The Human Need for Oxygen 13 2.4 Nitrogen 15 2.5 Carbon Dioxide 16 3 The Adrenalin Rush and Feeling Superhuman 17 4 Carbon Monoxide – A Nasty and Sinister Gas 21 4.1 Threshold Limit Value (TLV) 26 5 A Most Unpleasant Smell 27 6 The Hydrocarbons 33 6.1 Flammability of Hydrocarbons 34 6.2 More Waxy and Viscous Fluids 37 6.3 Hydrocarbon Vapours and Flammable Limits 37 Fresh Air in Dark Places vi 6.4 The Chemical Industry and Alkanes 40 6.5 Benzene 42 6.6 CFCs 43 6.7 Ammonia 45 6.8 Release of Gases from Residues on Chemical Tankers 45 7 So Far, So Good, So What? 47 8 The Real World 53 8.1 Hazard Identi?cation 56 8.2 Risk Assessment 56 8.3 Checklists 57 8.4 Signed Entry Permit 58 8.5 Correctly Monitor and Record 60 9 Tables of Toxicity 75 9.1 Source of Data 76 9.2 TLV, TWA and STEL 79 9.3 OEL, MEL, WEL and DNEL 82 10 The Nose is not Enough 85 10.1 Introduction to Explosimeters 86 10.2 Introduction to the Oxygen Analyser 90 10.3 Introduction to the Tankscope 91 10.4 Tubes and Multi-Channel Gas Detectors 92 10.5 Testing and Calibration of Instruments 96 10.6 Summary of the Various Gas Measuring Instruments 96 10.7 Flammable Range Diagram 97 11 Closing Summary 99 11.1 Key Points when Preparing to Evaluate the Atmosphere in a Compartment 99 11.2 Evaluating the Atmosphere of Secondary Locations 101 Bibliography 105 vii Authors’ Introduction The authors, Olaf and Erik Olsen, ?rst considered this book after reading yet another account of an enclosed space tragedy resulting in the fatality of merchant seafarers. Despite the fact that the merchant marine world has been provided with guidance, regulation and codes to prevent such accidents, they still continue to happen. A ship is a collection of spaces, whether they are con?ned, enclosed, dangerous or otherwise, and most must be entered at some time for cleaning, inspection or maintenance. People on board a ship, particularly at sea, operate in one of the healthiest work locations known, but these routine activities can cause the death of a seafarer in a matter of minutes. It is with this in mind that the description of ‘dark places’ comes to mind. Rather than producing yet another set of best practices, it is hoped that the informative style of this book explains the hazards associated with the activity of entering con?ned spaces. Olaf has a Master Mariners certi?cate and draws on his career experience on tankers and dry cargo ships, together with considerable time in commercial ship management, in maritime education and in his work as an advisory consultant to several international maritime bodies. Erik is a graduate in health science combining commercial management and broad maritime transport knowledge. As authors providing the manuscript for this book, Olaf and Erik are very mindful of the constructive and very bene?cial editorial work done by the staff at Witherby Seamanship and thank all involved accordingly. March 2010 viii Foreword In 1947, Alistair Rattray worked in ship construction on the River Clyde in Scotland. Working in con?ned spaces, he quickly realised the importance of having equipment that would reliably and safely alert personnel if a ?ammable atmosphere was present. Consequently, he formed Gas Measurement Instruments Limited (GMI), a company which is proud to have maintained close links with the marine industry. Sixty three years later, there is still a risk of fatalities, severe injuries or illness when working in con?ned spaces compared to any other type of work in ships. As the need to enter con?ned spaces remains, a thorough understanding of the associated risks and requirements is essential. In writing this book, Olaf and Erik Olsen have embarked on a personal voyage to illuminate “dark places” using considerable experience and knowledge. Indeed, their deep understanding of con?ned space working, gained from ship experience, extensive training and interfacing with ship and shore personnel, has allowed the production of a book which is written in plain English making it easy to understand and importantly, allowing it to be readily put into practice. It is interesting to note that the style of this book in many ways emulates the characteristics of successful gas detection equipment used to evaluate atmospheres onboard ships. This includes ease of use and understanding, while maintaining reliability and accuracy. This book will undoubtedly be read from cover to cover by those wishing to develop a greater knowledge of con?ned spaces but additionally it can be used as a reference source by all personnel in the industry – a value that Gas Measurement Instruments is proud to be associated with. Ken McDermott Marine Product Manager Gas Measurement Instruments Ltd. Fresh Air in Dark Places 40 So far, saturated hydrocarbon structures have been discussed, the bulk of which are ?ammable. It has been shown that the boiling point, molecular mass and carbon to hydrogen balance are interrelated. 6.4 The Chemical Industry and Alkanes In the chemical manufacturing industry, the saturated, paraf?nic hydrocarbons are known as aliphatic (oily) alkanes. The word paraf?n was used as a trade mark name for light oils extracted from shale and used as lamp oil. Also known as kerosene or wax oil, it is used mainly for light products extracted from crude oil. The aliphatics can also present as an alkene or alkyne unsaturated, ole?nic substance. These are molecular structures that are unsaturated with hydrogen or other elements and are more active in their ability to react with the materials they come into contact with. Examples include ethene/ethylene, propene/propylene, butene/ butylene etc. The unsaturates in their simplest form are identi?ed by the suf?x -ene rather than the alkane-ane. 41 The Hydrocarbons This means that an operator must look carefully at reference documents and hazard data sheets to be aware of the facts. The unsaturated ‘enes’ are usually more aggressive to a person’s health than the saturated ‘anes’. The saturated alkanes like methane, ethane, propane and butane are not listed as severely toxic substances. However, a person can be asphyxiated by a high concentration exposure and in smaller concentrations it is likely to cause the effect of apparent drunkenness. When exposed to these hydrocarbons, there is a risk of misguided action, poor judgement and increased high spirits. The victim will tire rapidly and become exhausted, possibly falling over semi-conscious suffering hydrocarbon narcosis. The majority of hydrocarbon gases and vapours, although very ?ammable, are not regarded as toxic. However, an example of these gases causing death was sadly experienced when two ship inspection personnel succumbed to methane asphyxiation after entering a coal ship’s cargo hold, without permission and without gas atmosphere evaluation having been carried out. A group of people suffering from hydrocarbon narcosis may all be in a similar stupe?ed condition, without realising the danger they are in. This is one of the main reasons why whenever anyone is inside a con?ned space there must be a watchful standby communications person at the entrance to the space, in fresh air for the entire time. They should frequently communicate and test the entrants’ reactions until they re-emerge. If con?ned space entrants are exposed to more aggressive unsaturates, the effect on them can be rapid and similar to an anaesthetic. After being overexposed to the simpler saturated hydrocarbons, a person may recover by being moved into fresh air. They are likely to have a prolonged headache, tiredness and possible nausea. The greater the exposure concentration, the greater the effect. Fresh Air in Dark Places 42 6.5 Benzene The descriptions have so far concentrated mainly on aliphatic oil- based hydrocarbons, but aromatic hydrocarbons should also be considered. In carbon chemistry, a natural and physical form of six carbon atoms may form in a cyclic mode. In a saturated condition, this would be cyclohexane, this relates to cellulose and glucose as well as other possibilities. In the unsaturated version, this leads to a building block of organic chemistry. When the benzene phenyl ring is added to other elements, molecules and more benzene, many of today’s modern synthetic substances are produced. Many benzene derivatives are toxic and some, including benzene itself, toluene and xylene, which are often associated with paint coatings, are listed as carcinogens. The number of structures in this group is in?nite and they often carry sulphur or nitrogen, creating complexities in their aggression. They, along with another group of products called the halogenated hydrocarbons, are often dif?cult to measure as a gas and to evaluate in the atmosphere because of their readiness to react with tank residues and change into other substances. The measurement of benzene can be tricky as it is a solvent capable of bonding with many other residues in solid, liquid or vapour form. As a toxic substance, benzene is a well known carcinogen that is capable of accumulating in human tissue and aggressively affecting the system. Over the years, the solvency power of benzene was underestimated, which resulted in much higher permitted safe exposure thresholds than are practised today. Indeed, the TLV (see Section 9.2) of benzene was at one time 25 ppm for a person in exposure over a 43 The Hydrocarbons 40 hour week and, as years passed, this ?gure was progressively reduced in stages of 15, 10, 5 and 3 and nowadays is as low as 1 ppm in most health and safety guidelines. 6.6 CFCs A number of halogenated hydrocarbons have been identi?ed as environmentally aggressive and their manufacture progressively banned under the label of chloro?uorocarbons, CFCs. The elements ?uorine, chlorine, bromine and iodine are known as halogens. They have a valency of one and are able to take up vacant unsaturated slots in an ole?nic hydrocarbon structure, displacing other less reactive structures. This creates several products. Halogens such as chlorine gas are toxic, as are the products associated with them. An example is vinyl chloride monomer (VCM) carried in gas ships as a bulk cargo and used mainly in manufacturing polyvinyl chloride (PVC). As in the case of benzene, vinyl chloride is a toxic substance that has received more stringent health and safety guidance through the years, with its TLV being tightened to a ?gure of 3 ppm in most industrial countries. It is also important to mention that the authorities dealing with guidance on toxic substances such as benzene and vinyl chloride monomer have all regularly revisited their information and written in much more detail than is incorporated in this guide. It is for that reason that a reference bibliography containing such additional information is added as a ?nal chapter.