SAFETYand HEALTH inCONFINED SPACES Neil McManus, CIH, ROH North West Occupational Health and Safety North Vancouver, B. C. Canada Published in 1999 by CRC Press Taylor & Francis Group 6000 Broken Sound Parkway NW, Suite 300 Boca Raton, FL 33487-2742 © 1999 by NorthWest Occupational Health and Safety, a division of Training by Design, Inc. CRC Press is an imprint of Taylor & Francis Group No claim to original U.S. Govermnent works Printed in the United States of America on acid-free paper 1098765432 International Standard Book Number 1-56670-326-3 (Hardcover) This book contains information obtained from authentic and highly regarded sources. Reprinted material is quoted with permission, and sources are indicated. A wide variety of references are listed. Reasonable efforts have been made to publish reliable data and infonnation, but the author and the publisher carmot assume responsibility for the validity of a11 materials or for the consequences of their use. No part of this book may be reprinted, reproduced, transmitted, or utilized in any form by any electronic, mechanical, or other means, now knoWll or hereafter invented, including photocopying, microftlming, and recording, or in any information storage or retrieval system, without written permission from the publishers. Trademark Notice: Product or corporate names may be trademarks or registered trademarks, and are used only for identification and explanation without intent to infringe. Library of Congress Cataloging-in-Publication Data Catalog record is available from the Library of Congress Visit the Taylor & Francis Web site at IIII informa http://www.taylorandfrancis.com I and the CRC Press Web site at Taylor & Francis Group is the Acadernic Division of T&F Tnforrna pie. http://www.crcpress.com Preface Confined spaces are the sites of many fatal and non fatal industrial accidents. Given appropriate conditions, potentially any space in which people work could be or could become a confined space. We know very little about accidents involving confined spaces. Publicly available information exists primarily as a result of investigations of fatal accidents. NIOSH (National Institute for Occupational Safety and Health), OSHA (Occupational Safety and Health Administration), and MSHA (Mine Safety and Health Administration) reports are the main resources for research in this area in North America. According to the most recent statistics provided by NIOSH, engulfment by loose materials caused 65% of the fatalities in workspaces normally called confined spaces, as weIl as excavations, trenches, and ditches. While excavations, trenches, and ditches normally are not considered to be confined spaces in regulations and standards, engulfment is engulfment, regardless of the semantics about location and type of material. Atmospheric hazards caused about 56% and engulfments about 34% of the fatalities in workspaces recognized as confined spaces. Drowning, electrocution, fall from heights, process-related accidents, plus other causes constituted the remaining 10%. The overwhelming cause of the very few process-related accidents was failure of live steam (utility) lines during work of an unrelated nature. The most glaring deficiency identified in the reports from NIOSH, OSHA, and MSHA was lack of knowledge. Workers and supervision routinely failed to recognize the hazardous conditions that existed or could develop in these workspaces. This problem continues and will continue, despite the enactment of comprehensive legislation in industrialized countries. Confined spaces differ from normal workspaces. One reason for this is the role of boundary surfaces. Containment by boundary surfaces amplifies or magnifies the severity of hazardous conditions. The relationship between the individual, boundary surfaces, and the source of energy or contamination or other hazardous condition is the major factor in the on set, outcome, and severity of accidents in confined spaces. Another important factor is the function of the structure within which the space exists. Some structures act as a protective baITier between energy sources, such as machinery, and the sUITound ings. Other structures contain processes. Others contain or store substances and materials. Many of the conditions that occur in these spaces are unique and are not encountered in ordinary workspaces. Confined spaces also include temporary structures, such as excavations and ditches. A disturbing number of fatal accidents occuITed in spaces that lay outside conventional defi nitions of confined spaces. Without accommodation of these realities by standard-setters and regulators, accidents involving this type of space will continue to OCCUf. Some examples include: • A mould used to manufacture 150-L (40-gal U.S.) plastic containers: the victim inserted head and shoulders into the mould (50 cm diameter by 80 cm deep) and was overcome by vapor from the perchloroethylene that he used to wipe the surfaces. • A waist-high paint mixing pot: the victim bent into the pot and was overcome by vapor from the methylene chloride that he used to clean the interior. • The shaft of a dumbwaiter: the victim opened the door to determine the location of the car and was struck by it. • A sand-mixing machine: the victim reached into a side hatch to repair a bearing and was struck by the bl ades when the drive motor started unexpectedly. • "Empty" 200-L drums: ignition ofthe hazardous atmosphere contained in these drums from residual contents caused about 16% of the fatal welding and cutting accidents. • An open-topped degreaser: the victim reached in over the top of the degreaser (2 m x 3 m x 1.5 m high) to recover apart that had fallen in and was overcome by the solvent-rich, oxygen-deficient atmosphere. • The cabinet of an abrasive blasting machine: the operator walked in through the access door to retrieve a part that had fallen and was asphyxiated by the nitrogen atmosphere used to inert the interior. • An office: a carpet layer sealed off the ventilation system, as weIl as gaps in walls and doors, to contain solvent vapors from adhesive used to anchor carpet tiles. He was overcome by toluene vapor. Traditional definitions for confined spaces have focused on structures, not conditions. This then begs the questions: what exactly is a confined space and how should management of hazardous conditions occur? The test for effectiveness of a particular definition is simple: does it encompass all of the workspaces in which the hazardous conditions peculiar to confined spaces could exist or could develop? This definitely is not the case with definitions used in present regulatory and consensus standards. Standards and regulations that fail to encompass the unusual workspaces in which people work leave open the dOOf for future tragedies. Work in confined spaces generally occurs during construction, inspection, maintenance, mod ification, and rehabilitation. This work is nonroutine, short in duration, nonrepetitive, and unpre dictable in scheduling (often occurring during off-shifts and weekends). Hazardous conditions in confined spaces follow several themes: confinement of individuals, confined atmospheres, confined energy, and the amplified expression of health, safety, biological, and ergonomic hazards. A major difficulty with the management of hazardous conditions in confined spaces is the fluid nature of the problem. A seemingly minor change or error or oversight in preparation of the space, selection, or maintenance of equipment or work activity can change the status of conditions from innocuous to life-threatening. The term "confined space" itself has contributed to the problem. The term strikes fear into management because of the considerable administrative and technical burdens imposed by regula tions onto workspaces that receive this label. The incentive not to label a particular space as a confined space, therefore, is considerable. This reality has distorted the manner in which confined spaces should be viewed. Conditions in some confined spaces are life-threatening at all times. On the other hand, conditions in many other confined spaces are life-threatening only under unusual circumstances. Surely, the determinant that should govern the nature of the response to a particular circumstance is the level of concern appropriate to a particular condition and not the worst case. Yet, the typical depiction of work practices conveyed in artic1es in trade magazines and other sources and in advertising for products is the latter. Hazard assessment is a device for identifying potential and actual hazardous conditions and assessing the level and acceptability of risk. Hazard assessment is a difficult process. Many of the conditions that can produce acute exposure or traumatic injury are difficult to recognize and assess. Hazard assessment is semiquantitative at best and intuitive at worst. Yet, as indicated by real-world accidents, the tolerance for error in judgment is very small. The operating cyc1e of many confined spaces is divisible into the following segments: the undisturbed space, preentry preparation, prework inspection and work activity. A hazard assessment performed for each provides the best way to maximize control over conditions. The undisturbed space is the status quo established between c10sure at the end of one work cyc1e and the start of preparation for the next. Preentry preparation is the sum of activities undertaken to ready the space for entry. Activities undertaken during preentry preparation should minimize the risk of entry and performing work through hazard elimination, or at the least, control. Prework inspection is the initial entry into the space. (Prework inspection is a requirement in some jurisdictions.) The purpose for prework inspection is to ensure that the space is safe for the start of work. Work activity describes the individual tasks to be performed by entrants. Hazards that remain at the start of work activity or are created by it dictate the nature of possible accidents for which emergency response is required. Performing the hazard assessment for each segment of work is essential to the process. A hazardous condition eliminated during preentry preparation could reappear as a result of work activity. Adecision about whether the risks associated with entry and work are acceptable is essential to the process. If control of conditions can be assured, the decision is not difficult to make. The less the level of perceived control, the greater becomes the need for contingencies. The only other alternative is to prohibit the entry. This decision highlights a question that deserves to be asked, but is easily overIooked: should entry occur at all? This question receives little attention in discussion about confined spaces. Consensus and regulatory standards have delegated the onus for hazard assessment and spec ification of control measures to the qualified person. The qualified person is deemed capable by education and/or specialized training and experience of anticipating, recognizing, and evaluating hazardous conditions and specifying control measures and/or protective actions. That is, the qual ified person is expected to know what to do in the context of a particular situation. Two models for the on-site management of hazardous conditions in confined spaces have evolved: the entry permit system and the on-site qualified person. Clear lines of authority, respon sibility, and accountability are required under either system. The entry permit summarizes actions and tests performed and indicates the need for precau tionary measures. The permit also specifies procedures to folIowand conditions under which entry and work can proceed. The entry permit also acts as the summary for the complete hazard assessment. The permit system works best where hazardous conditions are known from previous experience and control measures have been tried and proven effective. The permit system enables apportioning of scarce expert resources in an efficient manner. The limitations of the permit system arise where previously unrecognized hazards are present. If the qualified person is not readily available, these can remain unaddressed. The on-site qualified person provides readily available expertise for evaluation of conditions and control measures. A major advantage of this approach is the ability to respond to unanticipated situations on short notice. Following evaluation of the space and implementation of control mea sures, the qualified person issues a certificate. The certificate indicates tests performed and condi tions under which the work can proceed. The certificate also indicates the status of the space in standardized language, such as "safe for workers." This approach is ideally suited to operations that have numerous confined spaces or where conditions or the configuration of spaces can undergo rapid change. The limitation of this approach is the knowledge base of the qualified person and the skill and thoroughness in its application. The preceding discussion highlights some of the challenges posed by confined spaces. There is a serious need to unify the themes that exist within this subject area. This subject area is fragmented by industrial sector. Little, if any, crossover occurs between them. This is most unfor tunate, since hazard management models that work in one industrial sector may work just as weil in another. The blockage to intersectoral application of these models is regulatory. Application of narrowly focused hazard management models across a broad spectrum of industry does not nec essarily benefit all applications. Open discussion and consideration are essential to ensure that organizations can utilize the hazard management model that best suits their needs. In order to achieve this objective, the entire spectrum of the subject of confined spaces must be brought forth for discussion. Only in this manner will the needless tragedies that continue to occur provide some useful lessons for the future. Writing a book on confined spaces involves some difficult creative decisions because this subject does not progress from A to Z in linear fashion. The stylistic decisions are fundamental: either refer continually to material in other sections and avoid repetition or repeat some material to maintain continuity of thought. This book uses the lauer approach in the hope that this will be easier to use for the greatest number of readers. The casual reader should be able to begin in many areas with enough peripheral information to be able to put the topic of interest into perspective with other issues. The Author Neil McManus is a practlcmg industrial hygienist with 20 years of broad-spectrum service "in the trenches" to workers and management. He is certified in the compre hensive practice of industrial hygiene by the American Board of Industrial Hygiene and by the Canadian Registration Board of Occupational Hygienists. Mr. McManus is a member of the American Conference of Govemmental Industrial Hygienists, Amer ican Industrial Hygiene Association, British Occupational Hygiene Society, Health Physics Society, and the Marine Chemist Association. He has been an active volun teer in committees in the industrial hygiene profession and in the local community, and has written numerous articles and short pub lications. Mr. McManus has an M.Sc. in radiation biology and an M.Eng. in occupa tional health and safety engineering, as weH as a B.Sc. in chemistry and a B.Ed. special izing in chemistry and biology. Mr. McManus became interested in maintenance activities in confined spaces during tumarounds in an oil refinery in the early 1980s and foHowed this through sub- sequent employment in electrical generation, railway operations, and ship consfruction. He has taught courses on confined space hazards and made numerous presentations at meetings and conferences on this theme. He is a long standing member and former Chair of the Confined Spaces Committee of AIHA. Contri butors Robert E. Brown, Jr., CIH, CHMM Robert E. Henderson Dexter Corporation Director of Marketing Pittsburg, CA Biosystems Inc. Middletown, CT Richard P. Garrison, Ph.D., CIH, CSP Associate Professor of Industrial Health School of Public Health Michael S. Krupka, CIH Department of Environmental and Medfield, MA Industrial Health Ann Arbor, MI David T. Matthews, CIH John GilI, CIH Clayton Environmental Consultants Springfield, MA Kennesaw, GA Gilda Green Training by Design, Inc. David G. McCarthy North Vancouver, BC, Canada Beimont, MA Contents Chapter 1 Atmospherie Hazards and Fatal Aeeidents in Confined Spaees Chapter 2 Nonatmospherie Hazards and Fatal Aeeidents in Confined Spaees ............................................... 39 Chapter 3 Toxie and Asphyxiating Hazards in Confined Spaees .................................................................... 65 Chapter 4 Ignitable and Explosive Atmospherie Hazards .............................................................................. 111 Chapter 5 Atmospherie Confinement: The Role of Boundary Surfaees ....................................................... 161 Chapter 6 Nonatmospherie Hazardous Conditions: The Role of Confined Energy ...................................... 209 Chapter 7 Hazard Management for Confined Spaees .................................................................................... 243 Chapter 8 Preentry Planning, Hazard Assessment, and Hazard Management .............................................. 271 Chapter 9 Logistieal Considerations for Work Involving Confined Spaees .................................................. 353 Chapter 10 Instrumentation and Testing ........................................................................................................... 397 Robert E. Henderson Chapter 11 Ventilation for Work in Confined Spaees ..................................................................................... .467 Chapter 12 Respiratory and Other Personal Proteetive Equipment.. ............................................................... 509