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Copyright WTCB, Brussels, Belgium All rights reserved. No part of this publication may be reproduced without the prior written permission of BBRI. It is allowed to quote data from this publication, provided that the source of the quotation is clearly mentioned. Although all care is taken to ensure the integrity and quality of this publication and the information herein, no responsibility is assumed by the publishers, the authors or the European Community for any damage to property or persons as a result of operation or use of this publication and/or the information contained herein. This publication does not necessarily represent the opinion of the European Community.

Technical Report Part 1

Design Fire Scenarios Rapporteur Alfred Haack, STUVA

Thematic Network FIT Fire in Tunnels is

supported by the European Community under the fifth Framework Programme

Competitive and Sustainable Growth Contract n G1RT-CT-2001-05017

Thematic Network FIT Fire in Tunnels

Overview of the FIT reports

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Overview of the FIT reports The Thematic Network FIT Fire in Tunnels aims to establish and develop a European platform and optimise efforts on fire safety in tunnels. The Networks ambition is to develop a European consensus on fire safety for road, rail and metro tunnel infrastructures and enhance the exchange of up-to-date knowledge gained from current practice and ongoing European and national research projects. The outcome of the FIT network is presented in 3 complementary formats:

FIT website (www.etnfit.net) General report Technical Reports on

o Design fire scenarios; o Fire safe design; and o Fire response management

The FIT website (www.etnfit.net) contains the 6 consultable databases, the co-membership, the presentations of the International Symposium on Safe and Reliable Tunnels (Prague 2004) and the technical reports. The reports are available after registration as a corresponding member. The General report presents the outcome of the FIT activities. After the introduction of the FIT Network, the general approach to tunnel fire safety is presented. This chapter can be considered as a strategic introduction to the consecutive safety aspects and the integrated approach to safety in tunnels. It introduces the highlights of the technical reports of the FIT network with the executive summaries on design fire scenarios, fire safe design and fire response management. The Technical reports on the FIT workpackages presents the detailled reflexion and results of the network on the items in more then 450 pages state of the art research work. The reports are available from the FIT website after registration as a corresponding member.

Technical report Part 1 Design fire scenarios describes recommendations on design fire scenarios for road, rail and metro tunnels. Design fires to cover different relevant scenarios (e.g. design fires referring to the evacuation of people, design fires referring to ventilation purpose or design fires referring to the structural load) are presented and recommended. In Technical report Part 2 Fire Safe Design, a compilation of relevant guidelines, regulations, standards or current best practices from European member states (and important tunnel countries like e.g. Japan and USA) is given. The analysis is focused on all fire safety elements regarding tunnels properly said and are classified according to the transport nature: road, rail and metro. The occurrence of a fire in a tunnel provokes a need for response from the tunnel users, the operators and the emergency services. The Technical report Part 3 Fire response management presents the best practices which should be adopted by these different categories to ensure a high level of safety.

Overview of the FIT reports

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The Technical reports on the FIT workpackages presents the detailled reflexion and results of the network on the items in more then 450 pages state of the art research work. The reports are available from the FIT website after registration as a corresponding member.

Technical report Part 1 Design fire scenarios Rapporteur Alfred Haack, STUVA The technical report of FIT Work Package 2 is devoted to design fire scenarios for road, rail and metro tunnels. It collects data from different countries (e.g. Germany, France, Italy, UK), international organisations (e.g. PIARC, ITA, UPTUN) as well as from the experiences in individual tunnels (e.g. Mont Blanc, Tauern, Nihonzaka, Caldecott, Pfnder). The report includes basic principles of design fires, tunnel fire statistics and impacts of fires and smoke in tunnels on people, equipment and structure. The data is analysed and different sets of data are compared to ascertain the degree of confidence attributed to the information. Recommendations are made within the text on specific issues when this was deemed appropriate and reliable. Technical report Part 2 Fire Safe Design Rapporteur Bruno Brousse, CETU Fire Safe Design Road Niels Peter Hoj, COWI Fire Safe Design Rail Giorgio Micolotti, RFI Fire Safe Design Metro Daniel GABAY, Arnoud Marchais, RATP The FIT Workpackage Compilation of guidelines for fire safe design presents the compilation of relevant guidelines, regulations, standards or current best practices from European member states, including reference documents from important tunnel countries like e.g. USA and Japan, or from European or international organisations, e.g. PIARC and UN/ECE. The report is classified according to the transport nature in three similar main sections: road, rail and metro tunnels. The three sections in the report presents the collected guidelines and regulations, their analytical abstract and table of content. About 50 safety measures are presented and compared related to structural measures (19), safety equipment (36) and structure and equipment with response to fire (3). For each type of measure the impact on safety is presented with a synthesis and a detailed comparison of the comprehensive list of safety measures. Technical report Part 3 Fire Response Management Rapporteur Norman Rhodes, Mott MacDonald The objective of the FIT Work Package 4 Best practise for Fire Response Management is the definition of best practices for tunnel authorities and fire emergency services on prevention and training, accident management and fire emergency operations. The occurrence of a fire in a tunnel provokes a need for response from the tunnel users, the operators and the emergency services. The technical systems which are installed in many tunnels are described in Chapter 2. These systems contribute to the possible levels of safety that can be achieved and are mentioned later in relation to response planning. The viewpoint of the fire brigade is then presented in Chapter 3 in order to establish the context of fire response management. Best practices for Road, Rail and Metro tunnels then follow in Chapter 4, 5 and 6 respectively. They are presented according to the conceptual phases before, during and after a fire, taking into account the different involved parties (users, operators and emergency services).

Table of contents

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Table of contents Chapter 1 : Introduction 19 1.1 Design fire objectives 19 1.2 Characteristics of design fires 21

1.2.1 Input parameters and fire development phases 21 1.2.2 Classification of design fires based on design fire scenario analysis 23 1.2.3 Pre-flashover design fires 23 1.2.4 Fully-developed (fuel- or ventilation- controlled) fires 24 1.2.5 Smouldering fires 25 1.2.6 Parametric fires 25

Chapter 2 : Hazards by fires 27 2.1 Statistical overview of Real Fires and Fire Effects 27

2.1.1 Frequency of Fires in Tunnels 27 2.1.2 Analysis of selected Fires 27

2.2 Fire impact on human beings [94] 32

Chapter 3 : Existing Standards and Proposals on Design Fires 39 3.1 Design Fires for Road Tunnels 39

3.1.1 The Course of some real Fires in Road Tunnels 39 3.1.2 Evaluation of fire growth rate and peak HRR 53 3.1.3 Design fires referring to the structural load of Road tunnels 61 3.1.4 Design Fires referring to the Ventilation of Road Tunnels 78 3.1.5 Design Fires and Road Tunnel Equipment 80 3.1.6 Design Fires referring to the Rescue of Road Tunnel Users 81

3.2 Design Fires for Mainline Railway Tunnels 87

3.2.1 The Course of some actual Fires in Mainline Railway Tunnels87 3.2.2 Evaluation of fire growth rate and peak HRR from experiments91 3.2.3 Design Fires referring to the Structural Load of Mainline Railway

Tunnels 92 3.2.4 Design Fires referring to the Ventilation of Mainline Railway Tunnels 104 3.2.5 Design Fires referring to the Equipment of Mainline Railway Tunnels 105 3.2.6 Design Fires referring to the Rescue of Passengers in Mainline

Railway Tunnels 105

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3.3 Design Fires for Metro Tunnels 106 3.3.1 The Course of some actual Fires in Metro Tunnels 106 3.3.2 Evaluation of fire growth rate and peak HRR from experiments111 3.3.3 Design fires referring to the structural load of metro tunnels 112 3.3.4 Design Fires referring to the Ventilation of Metro Tunnels 116 3.3.5 Design Fires referring to the Equipment of Metro Tunnels 116 3.3.6 Design Fires referring to the Rescue of Passengers in Metro

Tunnels 117

Chapter 4 : Current Considerations in the EU Countries on Future Developments in the Fire Scenarios for Traffic Tunnels within the DARTS project [132 to 135] 121

4.1 Application of Natural Fire Safety Concept to Road, Rail and Metro Tunnels [132 to 135] 121

4.1.1 Fire characteristics contributing to natural fire curve 122 4.1.2 Structural behaviour 123 4.1.3 Parameters contributing to realistic structural load 124 4.1.4 Safety measures in the NFSC approach 125

4.2 Effect of ventilation on rate of heat release during fire tests in the Second

Benelux road tunnel 139 4.2.1 Fire development for cars [132, 135] 139 4.2.2 Fire development for vans 140 4.2.3 Conclusions from the Second Benelux tunnel tests 141

4.3 Summary 141

Chapter 5 : Conclusions 143 5.1 Introduction 143 5.2 Design fire objectives 143 5.3 Proposals for design fires 144

5.3.1 Road tunnels 144 5.3.2 Mainline railway tunnels 145 5.3.3 Metro tunnels 147

5.4 Future work 148

Chapter 6 : Bibliography 151

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FIT PARTNERSHIP

BELGIAN BUILDING RESEARCH INSTITUTE (BBRI) (Co-ordinator & WP1 leader on Consultable Databases) Johan Van Dessel Yves Martin www.bbri.be

BUILDING RESEARCH ESTABLISHMENT LTD (BRE) (Manager Database 3: Overview of numerical computer codes) Suresh Kumar Stewart Miles www.bre.co.uk

CENTRE FOR CIVIL ENGINEERING RESEARCH AND CODES/CENTRE FOR UNDERGROUND CONSTRUCTION (CUR/COB) Jan P.G. Mijnsbergen www.cur.nl www.cob.nl

ENTE PER LE NUOVE TECNOLOGIE, L'ENERGIA E L'AMBIENTE (ENEA) Franco Corsi www.enea.it

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GESELLSCHAFT FUER ANLAGEN- UND REAKTORSICHERHEIT(GRS) Klaus Kberlein

www.grs.de

HEALTH AND SAFETY EXECUTIVE (HSE) Richard Bettis www.hse.gov.uk

INSTITUTO DE CIENCIAS DE LA CONSTRUCCION "EDUARDO TORROJA" CSIC (IETCC) Angel Arteaga www.csic.es

INSTITUT NATIONAL DE L'ENVIRONNEMENT INDUSTRIEL ET DES RISQUES (INERIS) (Manager Database 2: Tunnel test site facilities) (Manager Database 5: Assessment reports on fire accidents) Guy Marlair www.ineris.fr

SP SWEDISH NATIONAL TESTING AND RESEARCH INSTITUTE (SP) Haukur Ingason www.sp.se/fire

NETHERLANDS ORGANIZATION FOR APPLIED SCIENTIFIC RESEARCH (TNO) Kees Both www.bouw.tno.nl

FIT Partnership


TECHNICAL RESEARCH CENTRE FINLAND (VTT) Esko Mikkola www.vtt.fi/rte/firetech

FIRE SAFETY ENGINEERING GROUP - UNIVERSITY OF GREENWICH (UOG) E. R. Galea http://fseg.gre.ac.uk

OVE ARUP PARTNERSHIP (ARUP) Paul Scott www.arup.com

COWI CONSULTING ENGINEERING AND PLANNERS AS (COWI) (General approach to tunnel fire safety & WP3 rapporteur Fire Safe Design - road) Niels Peter Hj Steen Rostam www.cowi.dk

DEUTSCHE MONTAN TECHNOLOGIE GMBH (DMT) (Manager Database 4: Data on safety equipment in tunnels) Horst Hejny Werner Foit www.dmt.de

FIRE SAFETY DESIGN AB (FSD) Yngve Anderberg Gabriel Khoury www.csic.es

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MOTT MACDONALD LIMITED (WP 4 rapporteur Fire response management) Norman Rhodes www.mottmac.com

SISTEMI ESPERTI PER LA MANUTENZIONE (SESM) Fulvio Marcoz www.sesm.it

STUDIENGESELLSCHAFT FUER UNTERIRDISCHE VERKEHRSANLAGEN E.V. (STUVA) (WP 2 rapporteur Design Fire scenarios) Alfred Haack www.stuva.de

FOGTEC BRANDSCHUTZ GMBH & CO KG Stefan Kratzmeir Dirk Sprakel www.fogtec.com

TRAFICON NV Ilse Roelants www.traficon.com

DRAGADOS CONSTRUCCION P.O., S.A. Enrique Fernandez Gonzalez Carlos Bosch www.dragados.com

FIT Partnership


HOCHTIEF AKTIENGESELLSCHAFT Hermann-Josef Otremba www.hochtief.com

ALPTRANSIT GOTTHARD AG Christophe Kauer www.alptransit.ch

CENTRE ETUDE DES TUNNELS (CETU) (Chair & WP3 rapporteur on Fire Safe Design) Didier Lacroix Bruno Brousse www.cetu.equipement.gouv.fr

FRANCE-MANCHE SA (EUROTUNNEL) Alain Bertrand www.eurotunnel.com

METRO DE MADRID S.A. Gabriel Santos www.metromadried.es

REGIE AUTONOME DES TRANSPORTS PARISIENS (RATP) (WP3 rapporteur Fire Safe Design - metro) Daniel Gabay Arnaud Marchais www.ratp.fr

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SUND & BAELT HOLDING A/S Leif J. Vincentsen Ulla Vesterskov Eilersen www.sundbaelt.dk

STOCKHOLM FIRE BRIGADE Anders Bergqvist www.brand.stockholm.se

KENT FIRE BRIGADE Ian Muir Manny Gaugain www.kent-fire-uk.org

LYON TURIN FERROVIAIRE (LTF) Eddy Verbesselt www.ltf-sas.com

RETE FERROVIARIA ITALIANA S.P.A. (RFI) (WP3 rapporteur Fire Safe Design rail) Giorgio Micolitti Raffaele Mele www.rfi.it

TECHNICAL UNIVERSITT GRAZ - INSTITUT FR VERBRENNUNGSKRAFTMASCHINEN (TUG) Peter-Johann Sturm www.virtualfires.org

FIT Partnership


FIT Co-membership The FIT partnership is strengthened with a co-membership (co-opted members and corresponding members) to receive ample feedback and input and obtain a larger forum for the dissemination of its outcome. The objectives of the corresponding and co-opted membership is the following:

provide a large platform for the FIT working items ensure European feedback and input via organizations active in 'fire in tunnels' ensure member-state support via national and regional representatives

Co-opted members are organisations invited to contribute to the FIT activities in a very intensive way. They have the same access level as FIT network members (working document, etc.). Co-opted members are bound by an agreement of collaboration and confidentiality. Seventeen organisation have been invited and agreed as FIT Co-opted members. Corresponding members further enlarge the FIT Network. Corresponding members are these organisations and national representatives that are interested to follow closely the activities of FIT and registered themselves via the FIT website. They have a priviliged access to the endorsed FIT working documents and the Consultable Databases on fire and tunnel. A FIT public working document is a draft document that is being prepared for final edition by the FIT network. It is made available for the FIT corresponding members for consultation, input and comment. More then 1200 corresponding members have been registered on the FIT website www.etnfit.net (status March 2005).

FIT CO-OPTED MEMBERS Amberg Engineering AG (Hagerbach test gallery) Contact name: Mr. Felix Amberg Rheinstrasse 4, Postfach 64, 7320 Sargans Switzerland Asociacion Latinoamericana de metros y subterraneos Contact name: Mr. Aurelio Rojo Garrido Cavanilles 58, 28007 Madrid - Spain CENIM - UPM Contact name: Mr. Enrique Alarcon Jos Gutirrez Abascal 2, 28006 Madrid - Spain Centro Ricerche Fiat Societa Consortile per Azioni Contact name: Mr. Roberto Brignolo Strada Torino, 50, 10043 Orbassano (TO) - Italy Railway Scientific and Technical Centre Naukowo-Techniczne Kolejnictwa Contact name: Mrs. Jolanta Radziszewska-Wolinska ul. Chlopickiego 50, 04275 Warsaw - Poland

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CTICM Contact name: Mr. Jol Kruppa Btiment 6 domaine de Saint Paul - 102 route de Limours 78471 Saint Remy-Les-Chevreuse - France Deutsche Bahn AG Contact name: Mr. Klaus-Juergen Bieger Taunustrasse 45, 60329 Frankfurt - Germany European Association for Railway Interoperability Contact name: Mr. Peter Zuber Boulevard de l'Impratrice 66 1000 Brussels - Belgium European Commission Directorate-General for Energy and Transport Contact name: Mr. Bernd Thamm rue de la Loi 200, 1049 Brussels - Belgium European Fire Services Tunnel Group (EFSTG) Contact name: Mr. Bill Welsh ME13 6XB Tovil, United Kingdom Eurovirtunnel Contact name: Mr. Gernot Beer Lessingstrasse 25/II, 8010 Graz - Austria Federal Highway Administration Contact name: Mr. Tony Caserta 400 Seventh Street S.W., HIBT-10 Washington, D.C. 20590 - USA Federal Ministry for Transport, Innovation and Technology Contact name: Dipl. Ing. Rudolf Hoerhan Stubenring 1, 1010 Wien - Austria Holland Rail Consult Contact name: Mr. Mark Baan Hofman Postbus 2855, 3500 GW Utrecht - The Netherlands Ministerie van het Brussels Hoofdstedelijk Gewest Contact name: Mr. Pierre Schmitz Vooruitgangstraat 80/1 1030 Brussels - Belgium Ministry of Transport, Public works and Watermanagement Contact name: Ir. Evert Worm PO Box 20.000 3502 LA Utrecht - The Netherlands Norwegian Public Roads Administration Contact name: Mr. Finn Harald Amundsen PO Box 8142 Dep 0033 Oslo - Norway


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Technical Report Part 1

Design Fire Scenarios

Rapporteur: Alfred Haack (STUVA)

Contributions: Alfred Haack (STUVA), Suresh Kumar (BRE), Didier Lacroix (CETU), Werner Foit (DMT), Horst Hejny (DMT), Franco Corsi (ENEA), Rudolf Hrhan (Federal Ministry for Transport, Innovation and Technology, Austria), Guy Marlair (INERIS), Arthur Bendelius (Parsons Brinckerhoff), Daniel Gabay (RATP), Haukur Ingason (SP), Kees Both (TNO), Ed Galea (University of Greenwich) Technical review: Gabriel Khoury (FSD) Workpackage Members Alfred Haack (STUVA), Yves Martin (BBRI), Suresh Kumar (BRE), Jan Mijnsbergen (CUR/COB), Horst Hejny & Werner Foit (DMT), Franco Corsi (ENEA), Angel Arteaga (IETCC), Guy Marlair (Ineris), Roger Dirksmeier (Fogtec), Klaus Kberlein (GRS), Richard Bettis (HSE), Haukur Ingasson (SP), Fulvio Marcoz (SESM), Kees Both (TNO), Ed Galea (University of Greenwich)


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Introduction


CHAPTER 1 : INTRODUCTION This is the final report of Work Package 2 of the European FIT (Fire in Tunnels) project devoted to design fire scenarios for road and rail tunnels. It collects data from different countries (e.g. Germany, France, Italy, UK), international organisations (e.g. PIARC, ITA, UPTUN) as well as from the experiences in individual tunnels (e.g. Mont Blanc, Tauern, Nihonzaka, Caldecott, Pfnder). The report includes basic principles of design fires, tunnel fire statistics and impacts of fires / smoke in tunnels on people, equipment and structure. The data is analysed and different sets of data are compared to ascertain the degree of confidence attributed to the information. Recommendations are made within the text on specific issues when this was deemed appropriate and reliable.

1.1 Design fire objectives Design fires and design fire scenarios are essential inputs required by a fire safety engineered approach to the fire safety design of new tunnels and any appraisal of fire protection measures in existing tunnels. Because of the shift from prescriptive to performance-based regulations, they have become the basis for the quantitative analysis of all aspects of tunnel fire design and accidental management. An effective fire protection design for life safety and property protection in tunnels requires a systematic assessment of a number of component sub-systems which contribute to the overall safety of the design. These sub-systems are: the initiation and development of fire spread, spread of smoke and toxic gases, detection and activation, fire service intervention and occupant evacuation, and possibly also adequate repair and retrofit conditions. Different fire protection measures are required at different stages of fire development, and these depend upon whether the system is designed for life safety or property protection (fire safety in the construction phase of the tunnels is not considered here). Further complexity arises due to the fact that the time scales for the response of active fire protection measures such as detectors and sprinklers are different from the response time of occupants during evacuation or the structural response time for structural integrity. Recently ISO (the International Organisation for Standardisation) has also published documents on design fire scenarios [157, 168]. Part 2 of the Standard ISO/TR 13387 covers Design fire Scenarios and Design Fires and outlines important principles and aspects that need to be considered for the provision of fire safety primarily for buildings [168]. These can equally apply to the fire safety in tunnels. The approach, however, ignores any constraints which might apply as a consequence of prescriptive national regulations or codes, and so may not necessarily mean compliance with national regulations unless they permit a performance-based approach. Following ISO/TR 13387, a design fire is an idealisation of a real fire that might occur, and a design fire scenario is the interaction of the design fire with its environment, which includes the impact on the fire of the geometrical features of the tunnel, the ventilation and other fire safety systems in the tunnel, occupants and other factors. Generally principles for fire safety engineering may apply for tunnels; however essentially the approach in the ISO document applies to buildings in which the compartimentalisation strategy can be applied; i.e. pre-dominantly the safety is guaranteed by comparting or limiting the fire to the room in which it originates sufficiently long enough to allow evacuation and fire brigade intervention.

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Such a strategy is however hardly possible in tunnels, in which generally speaking there is only one compartment, unless current developments of tunnel plugs, water curtains etc. would eventually succeed in providing discret sections within the tunnel to extinguish fires and prevent smoke reaching people. Work on such ideas is currently in progress in the European project UPTUN (UPgrading TUnnels). At this stage, such technologies have not yet been fully developed. A design fire scenario would typically define the ignition source and process, the growth of fire on the first item or vehicle ignited within the tunnel, the subsequent possible spread of fire, the interaction of the fire with its enclosure and environment, and its eventual decay and extinction. The PIARC report [36] states clearly that there should be more focus on the definition of appropriate fire scenarios dealing with specific aspects of tunnel fire safety. This can be achieved by accurate specification of the input and output characteristics of design fires, which are discussed in detail in the next section. The main cause of death in fire is related to smoke and hot gases inhalation and not to the fire itself. With respect to life safety, therefore ample attention should be given to the determination and mitigation of spread of (possibly toxic) hot gases and smoke. Some key design fire scenarios relevant to the fire safety in tunnels are listed below: (1) Design fire scenario for ventilation design and assessment Smoke ventilation in tunnels needs to be designed on the basis of smoke flow rates, i.e. the volume flow in the fire plume, from a design fire and local gas temperatures downstream from the design fire since they determine the volume flow rates which need to be vented. The design fire scenario should take into account all important factors such as ambient conditions, wall properties, and the efficient operation of detection and ventilation systems, which can have significant influence on the appropriate design fire characteristics. Although design fires can also be related to the critical confinement velocity in the design of exhaust ventilation systems, there is experimental evidence from large-scale fires tests [167] that for large fires, the critical velocity becomes independent of fire size. Furthermore, assumptions and regulations in the choice of design fire for design of ventilation system differs between different countries, especially for large fires. (2) Design fire scenario for egress analysis Evacuation measures for tunnel users or emergency rescue service need to consider breathable gas temperatures and concentration of toxic gases at head height in the tunnel as well as the effect of thermal radiation down onto evacuees from the hot gases at high level in the tunnel. The times for hazardous conditions to develop at particular locations needs to be compared with occupant egress times. These need to take into account the time it takes for occupants to realise they are in danger and begin their escape. Concern is related to the issue of stratification of hot gases and smoke. Expert opinions differ, and therefore we recommend to be careful and preferably avoid scenarios relying heavily on stratification. (3) Design fire scenario for thermal action on structures Initial data on design fires regarding the structural load are mainly based on fire tests executed in the context of the EUREKA project as reported in the PIARC report [36]. Currently ISO curves, Eurocode 1 curves, a so called hydrocarbon curve and still other different national design curves such as the Dutch 'Rijkswaterstaat Design Curve' are in use.

Introduction


Unfortunately none of these design criteria are universally accepted. Very important in this respect is to note that in general no appreciation of the real risks involved in adopting another curve is made. In the design fire scenario, instead of simply considering the fully-developed or steady-state phase, there can also be an advantage considering the various different phases of a design fire. (4) Design fire scenario for the safety of tunnel fire equipment In the existing regulations only a few hints are given to, for example, the temperature resistance of equipment in the case of a fire, often in relation to the ISO-temperature curve (Figure 3.3) and therefore not to specific tunnel fires. So a more precise framework together with the definition of design fires for testing purposes is needed. (5) Design fires for work on tunnel construction, refurbishment, repair and maintenance In the past fires related to, for example, tunnel boring machines and the refurbishment of tunnels. To cope with such incidents design fires for different work scenarios are needed. Within this report for the work package 2 of FIT the focus is on establishing design fires whereas guidelines etc. are discussed within work package 3 (see reports there). Also the results of other European projects like UPTUN must be taken into account as soon as they are available. Further the ISO work on design fires in general [157, 168] must be considered.

1.2 Characteristics of design fires 1.2.1 Input parameters and fire development phases Design fires, which are the basis of the design fire scenario analysis, are described in terms of variables used for the quantitative analysis. These variables typically include the heat release rate of the fire, yield of toxic species and soot as functions of time. Where the mathematical models used are not able to predict growth of fire and its spread to other objects within the tunnel traffic space or any other part of the tunnel, such growth and spread needs to be specified by the analysis as part of the design fire, or determined on experimental basis, preferably at a realistic scale. (1) Input characteristics Each design fire scenario is represented by a unique occurrence of events and is the result of a particular set of circumstances associated with active and passive fire protection measures. Accordingly, a design fire scenario represents a particular combination of events associated with factors such as: a) type, size and location of ignition source, b) distribution and type of fuel, c) fuel load density, d) type of fire, e) fire growth rate f) fires peak heat release rate g) tunnel ventilation system, h) external environment conditions, i) fire suppression j) human intervention(s)

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Design fires are further characterised in terms of the following variables as functions of time: a) fire characteristics (flame length, centreline velocity, radiation, convection, temperatures) b) critical confinement velocity for avoiding backlayering (only relevant in longitudinal ventilated tunnels) c) toxic species production rate d) time to key events such as fire spread from one vehicle to the next. Alternatively design fires can be characterised, for thermal actions on the tunnel structure and tunnel equipment, in terms of time-temperature curves that depend on the emissivity of the fire gases, surface temperature and emissivity of the walls. (2) Fire development analysis A full specification of a design fire scenario may include the following phases (figure 1.1): a) incipient phase characterised by a variety of fire sources, such as smouldering or flaming fire b) growth phase covering time of fire propagation up to flashover or full fuel involvement c) fully developed phase characterised by a substantially steady burning rate as may occur in ventilation or fuel controlled fire d) decay phase covering the period of declining fire severity e) extinction when there is no more energy being produced.

Figure 1.1: Schematic of a design fire scenario (axes: horizontal = time; vertical = hrr and/or

temperature)

Decay

INCIPIENT GROWTH Fully Developed DECAY

Sprinklered-controlled fire

Sprinklered Activation

Flashover

Introduction


1.2.2 Classification of design fires based on design fire scenario analysis Following ISO/TR 13387, different phases of the design fire scenario, illustrated in the above figure, can be used to define different design fires for meeting different design objectives. In contrast to building applications, where pre-flashover fires are of primary interest for life safety analysis, for tunnel applications, fully developed and flashed over fires are also of interest for life safety because of large distances involved as was the case in the Mont Blanc Tunnel fire disaster that consumed 26 vehicles and took 39 lives (in buildings, the strategy is to contain the fire in the room in which it originates; in tunnels there is only one compartment). Fully developed and flashed over fires also have an impact on the tunnel structure, tunnel equipment and structural components. In tunnels, significant flashover and fully developed phases are likely to occur in large fire incidents where multiple vehicles are involved. It should be emphasised that in contrast to the flashed over fires (arising in enclosed spaces) in buildings, a flashed over fire in a tunnel is unlikely to involve the whole tunnel length, but would be restricted to the vicinity around the seat of the fire. On the other hand, in tunnels the smoke spread will be in the area in which people have to evacuate. 1.2.3 Pre-flashover design fires Pre-flashover fires are of primary interest for life safety analysis, and can be influenced by active fire protection measures such as smoke control system or fire suppression systems. The incipient and the growth phase prior to flashover is referred to as the pre-flashover phase. The growth of a vehicle fire in a tunnel is highly depending on the arrangement of the combustibles and the way oxygen can be drawn in. As the fire grows in size, the rate of growth accelerates. If the fire remains localised to the item first ignited (or incident vehicle), the fire becomes fuel-controlled and decays. However, if the fire spreads to other combustible items (or vehicles), this may cause onset of rapid transition from a localised fire to the combustion of all exposed surfaces within the tunnel. The phenomenon of rapid transition driven largely by radiation feedback from the hot combustible and flammable gases collected under the tunnel roof and their sudden ignition. For design purposes, an exponential or power-law is often used for characterising the transient growth of the heat release rate for the pre-flashover fires. The most commonly used relationship is t2 fire, where the heat release rate of the fire grows with square of the time, of the form:

2

0

=

gttQQ (1)

where tg is referred to as the growth time, and represents the time for the fire to grow to the reference heat release rate 0Q& , where 0Q& can be used to represent the fully developed phase of the vehicles heat release rate. The rate of fire growth is subsequently modified by events that occur during the design fire scenario. These events can modify the heat release rate of the rate of the fire positively or negatively.

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Typical events and their effects are: a) Flashover extremely rapid acceleration from a localised fire to fully involved fire (fully

developed heat release rate) b) Deep hot layer acceleration c) Sprinkler activation steady or declining heat release rate d) Manual fire suppression steady or declining heat release rate e) Fuel exhaustion heat release rate decays to zero f) Changes in ventilation fire characteristics modified g) Fire service intervention fire characteristics modified h) Flaming debris subsequent ignition(s). Table 1.1 below gives the four categories of t2-fire growth commonly used in Great Britain for building fires.

Growth rate description Characteristic growth time, tg (s) Slow 600 Medium 300 Fast 150 Ultra-fast 75

Table 1.1: t-fire growth commonly used in Great Britain for building fires

These t2-fires can be modified appropriately for a particular tunnel fire scenario to take into account the factors described above. Considerable engineering judgement is required in selecting the appropriate category of fire growth. As an example, for liquid fuel spill from a vehicle fire on the floor, the ultra-fast growth description may be a good assumption for the fire growth rate. 1.2.4 Fully-developed (fuel- or ventilation- controlled) fires Fires with a significant steady-burning phase, such as following flashover, are referred to fully developed fires. The potential scenarios representative of such fires in tunnels could be, for example, a petrol tanker fire or post-crash fire involving multiple vehicles in a collision. When the fires reach fully developed phase, the rate of burning can be either fuel-controlled or ventilation-controlled. The transition from fuel-controlled to ventilation-controlled regime occurs when: mf = mox/s, (2) where mf and mox are respectively the mass fraction of fuel and oxidant, s is the stoichiometric oxidant to fuel ratio. It should be noted that usually apart from the close-vicinity of vehicle(s) on fire, tunnel fires are largely fuel-controlled, where their burning rate is controlled by the nature and geometrical arrangement of the fuel and not by the availabilty of air. However, there are exceptions such as the Mont Blanc Tunnel fire (1999) that became ventilation controlled due to the large number of vehicles being involved in fire.

Introduction


1.2.5 Smouldering fires A smouldering fire is caused by a combination of the following (input) parameters: a) Nature of fuel, b) Limitation of ventilation c) Strength of the ignition source The smouldering fire generally burns over a long period in limited ventilation conditions with little air entrainment, producing relatively low levels of heat but considerable unburned combustibles, higher concentration of smoke with relatively low visibility but large toxic products of combustion such as carbon monoxide and soot (e.g., burning of rubber tyres of vehicles involved in fire). The relatively low temperatures generated also mean that there is little buoyancy in the combustion products and thus little likelihood of smoke stratification under the tunnel roof as with hotter fires. Thus, the principal hazards posed by a smouldering fire are high concentration of carbon monoxide and low visibility conditions. The construction and combustible contents of a vehicle (e.g., electrical fault or overheating parts in its engine compartment) could be a potential source of a smouldering fire in tunnels. Seating materials in railway carriages with high fire resistance may also lead to a smouldering fire. 1.2.6 Parametric fires Parametric fires are the family of curves for the gas phase for different ventilation opening factors and fire load densities, which are usually expressed as time-temperature curves but can use heat release rates versus time curves. Since the parametric fires have been mainly derived from fires in small compartments using cellulosic-based fuels, their use for fires in tunnels should be used with caution. Prior to undertaking any fire scenario analysis, it is essential that the fundamental aspects of fire science and fire safety engineering, and limitations of the mathematical models used for hazard and risk analysis are clearly understood [168]. Recently some guidance has published on the use of advanced fire models based on the technique of computational fluid dynamics (CFD) [180] now being used quite frequently for tunnel fire safety design and assessment [169-172, 180, 181]. Note of caution: The success or acceptance criteria that appear in many of the tables presented in this report are in essence part of existing prescriptive standards that are accepted and in use in many countries around the world. However, it is essential to appreciate that many of these criteria are on the whole based on consensus opinion rather than reliable and representative engineering data. The information contained in these tables should thus not be automatically considered to be a reliable engineering basis upon which to base success or acceptance criteria for life safety or structural design.


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CHAPTER 2 : HAZARDS BY FIRES

2.1 Statistical overview of Real Fires and Fire Effects 2.1.1 Frequency of Fires in Tunnels Fire incidents in traffic tunnel systems are rare in relation to the total number of vehicle fires in several countries [36, 130, 206]. The following numbers are taken from a recent report by S. Kumar summarising fire incidents (road, rail) of 1994 to 1999 in the UK [163]. As a guide to likely numbers, the total number of arson fires (all vehicle types) in tunnels varies in the UK between 60 90 per year. This would be about 0.1 % of all vehicle fires, about 0.3 to 0.45 % of the vehicle fires with engines running and about 6.7 % to 10 % of the vehicle fires which follow a crash / collision [163]. 2.1.2 Analysis of selected Fires 2.1.2.1 Restrictions of the data base With regard to the rare frequency of vehicle fires in tunnels (chapters 2.1.1 and 4.1.1.4.1 as well as [36]) detailed reports about these fires are even more rare. In order to determine main fire causes it was necessary to include fires from various countries (e.g. USA, Japan, Great Britain) as well as fires which occurred sometime ago (i.e. between approximately 1970 and 1997) in the analysis of the fire events. One aspect which must be taken into consideration, among others, is that fires described in the sources available (e.g. investigation reports, fire service operational reports, publications in specialist journals, newspaper articles) are not always described in sufficient detail for the problems which occurred relating to fire protection and those encountered when fighting the fire to be adequately assessed. Furthermore, the technical developments during the assessment period also have to be taken into account. It is certainly possible that a fire which occurred in 1970 might not occur at all today, or certainly not take on the same proportions, as a result, for example, of the numerous improvements that have been made to vehicles in the intervening period. Against this background a total of 85 fires have been analysed in underground traffic systems. These selected fires are divided up as follows: - 45 fires in underground railway and suburban railway tunnels - 11 fires in main-line railway tunnels - 29 fires in road tunnels. Analysis of these fires brought to light the following main points of emphasis with respect to the causes of the fires and problems encountered in fighting the fires. 2.1.2.2 Causes of the Fires A significant proportion of the fires assessed were caused by vehicle defects: (1) approx. 40 % of the fires assessed (18 out of 45) in underground railway and suburban

railway tunnels (Figure 2.1) (2) approx. 82 % of the fires assessed (9 out of 11) in main-line railway tunnels (Figure

2.1) (3) approx. 62 % of the fires assessed (18 out of 29) in road tunnels (Figure 2.1)

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In the case of road tunnels therefore, approx. 62% of the fires assessed by STUVA were triggered by technical defects to vehicles. A further approx. 34% of the assessed fires were caused by rear-end collisions in road tunnels (Figure 2.3). These results essentially confirm the assessments carried out by PIARC/OECD on fires in road tunnels in the past 40 years (Figure 2.3) [1]. The slight deviations from the STUVA analysis (figure 2.3) are almost certainly attributable to the varying number of fire events assessed (STUVA 29 fires; PIARC/OECD 33 fires) and to the fact that some of the fires included in the analysis are of a different nature.

40

82

62

0

10

20

30

40

50

60

70

80

90

100

vehicle defects vehicle defects vehicle defects

metro tunnel railway tunnel(main line)

road tunnel

fires

[%]

Figure 2.1: Main Causes of the Selected Fires in Traffic Tunnels [74]

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51

3648

0102030405060708090

100

bad visibility(rescuing andextinguishing)

unfavourabletrain operation

on the line

bad ventilationduring

incident

metro tunnel railway tunnel(main line)

road tunnel

fires

[%]

Figure 2.2: Main Problems of Fire-Fighting in the Selected Fires in Traffic Tunnels [74]

5862

3634

6 4

0

10

20

30

40

50

60

70

Cau

ses

of fi

res

[%]

technical defects rear-end collisions others

PIARC / OECD

STUVA

Figure 2.3: Results of the PIARC / OECD Analyses of the Causes of Fires in Road Tunnels [74]

In the case of underground railway and suburban railway tunnels, another common cause of fires in addition to defects to vehicles was found to be arson (17 out of 45 fire events, approximately 50% of which were in the vehicles themselves, and the other approximately 50% at the stopping points)

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2.1.2.3 Problems encountered during Extinguishing and Rescue Work (1) Visibility The most frequently mentioned cause of delays to extinguishing and rescue work contained in the literature assessed relating to metro and road tunnels was poor visibility in the smoke-filled tunnel systems: a) 23 out of 45 fires in underground railway and suburban railway tunnels (Figure 2.2) b) The frequent poor visibility during fires in underground railway and suburban railway

tunnels is often related to the lack of forced ventilation. c) 12 out of 29 of the fires analysed in road tunnels Poor visibility in road tunnels resulted mainly from inadequate tunnel ventilation equipment and fire ventilation programs. It was not possible to find any details on the visibility during the fires in main-line railway tunnels during the extinguishing and rescue work in the documentation available for the analysis. (2) Technical Equipment of the Fire Services Problems with technical equipment of the fire services occurred mainly in fires in metro tunnels and road tunnels. The following are the main difficulties which occurred: a) Problems with the extinguishing water supply (9 out of 45 fires in metro tunnels, 7 out of

29 fires in road tunnels) b) Insufficient respiratory protection (4 out of 45 fires in metro tunnels, 5 out of 29 fires

in road tunnels) c) Inadequate two-way radio equipment (5 out of 45 fires in metro tunnels, 4 out of 29 fires

in road tunnels) In the documentation available referring to fire events in main-line railway tunnels there were no significant details of problems with the technical equipment of the fire services. Material DamaFires caused various types of damage to tunnel structures and tunnel equipment: (1) Concrete Spalling Concrete spalling was found in a total of 34 out of 85 fire events. Of these, 11 involved damage to underground railway and suburban railway tunnels, 3 cases of damage related to mainline tunnels (including the Channel Tunnel) and 20 cases were found in road tunnels. (2) Sagging of rectangular roof tunnel due to overheating of the steel reinforcement. This is particularly serious in underwater tunnels. (3) Damage to Tunnel Equipment In 42 out of 85 fire events there was damage to the tunnel equipment (e.g. electric cables, lighting, ventilators). Of these, 19 cases of damage related to underground railway and suburban railway tunnels, 2 cases to mainline tunnels and 21 to large conflagrations in road tunnels.

Hazards by fires


2.1.2.4 Problems with Tunnel Operation related to fire Problems with tunnel operation before and during the fire essentially occurred in the (1) Organisation of Tunnel Operation during the Fire In 21 out of 85 fire events analysed, problems occurred with the organisational

procedures of the extinguishing and human rescue work. (2) Vehicle Operation in Tunnels containing Rail Traffic In 12 out of 56 fires in rail traffic tunnels there were problems with organising the

transport operations in cases of fire (e.g. stopping vehicles not affected by the fire in good time). Of these 12 fires, 8 related to tunnel systems for underground railways and suburban railways and 4 related to mainline railway tunnels (Figure 2.2). In Germany there were only 2 fires in the underground railway and suburban railway field where there were problems with transport operations: a) up to and including 1987: 1 fire (1983, Munich) b) from 1988 on after introduction of the new BOstrab: 1 fire (1991, Herne)

(3) Ventilation in Road Tunnels In 14 of the 29 large fires analysed in road tunnels the ventilation equipment itself or

operation of the equipment proved to be insufficient (Figure 2.2). 2.1.2.5 Summary Analysis of the fire events therefore shows the following main points of emphasis: (1) Main Causes of Fires: a) Vehicle defects b) Arson (metro tunnels), decreasing tendency since increased demands on fire protection of the vehicles (e.g. DIN 5510) c) Rear-end collisions (road tunnels) (2) Problems with Extinguishing and Rescue Work: a) Poor visibility for the rescue workers (metro tunnels, road tunnels) b) Inadequate two-way radio connections during fire service operations (mainly in metro and road tunnels) (3) Main Aspects of Damage (additional to vehicles) a) Damage to concrete tunnel lining b) Damage to operational equipment (4) Problems with Tunnel Operations a) Inadequate organisation of tunnel operation in cases of fire b) Ventilation in road tunnels during large fires not ideal These practical issues have to be taken into account in the formulation of design fires.

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2.2 Fire impact on human beings [94] The products of combustion are many and varied. We generally lump fire products together and call the resulting mixture smoke. The smoke produced by fires is a volatile cocktail comprising, solid soot particles, unburnt or partially burnt fuel and a mixture of hot air and toxic gases. While the density, and chemical composition of the smoke produced by fires is dependent on the nature of the burning fuel, the total volume of smoke produced will depend on the physical size of the fire and the confines of the fire enclosure - in particular the height of the ceiling. The life threatening components of fire smoke are (1) obscuration causing loss of visibility, (2) toxic gases and (3) heat. (1) Obscuration: The obscuring nature of sooty smoke reduces visibility and the escape potential of fire victims. The effects of reduced visibility may be felt far away from the seat of fire origin. It is often this effect which is first noted by the victims of fire. Light obscuration is often expressed by the concept of optical density. This is a measure of the attenuation in intensity (I) of a beam of light traversing a distance L through the smoke. The optical density (OD) is defined by the non-dimensional parameter,

=

LIILogOD 0 (3)

where Io is the intensity of a standard light source and IL is the light intensity after passing a distance L through the smoke. Another measure of smoke concentration is the extinction coefficient (K). Both the OD and K relate to the level of smoke particles measured in the environment. In order to convert from the extinction coefficient to optical density per metre (OD/L), multiply OD/L by 2.3, i.e. K = OD/L * 2.3 [101, 102]. From these formulations the visibility can be approximated. The reciprocal of the optical density gives an indication of the level of visibility. Jin calculated that 2.0 divided by the extinction coefficient gave a conservative estimate as the visibility afforded by the environment [101, 102]. However, numerous figures can be used, according to the level of illumination, as well as other conditions. Jin [101, 102] conducted a series of experiments exploring the relationship between visibility in smoke and evacuation movement rates. Jins experiments were conducted in a smoke filled corridor some 20m long. The experimental population consisted of 17 females and 14 males with ages ranging from 20-51 years. Experiments were conducted using both non-irritant and irritant smoke. The subjects were asked to travel from one end of the corridor to the other, identifying when they could see a fire exit sign. Both the irritancy and the density of the smoke affected the volunteers walking speed.Figure 2.4 shows the gradual decline of the recorded walking speed through non-irritant smoke as the density of the smoke is increased, whereas in irritant smoke the gradient is far steeper. Jin explained this as being caused by the erratic movement of the volunteers due to their inability to keep their eyes open [101, 102]. Jin also noticed that the volunteers attempted to compensate for this lack of orientation by using the walls as guidance. Jins results suggest that in non-irritant smoke, walking speeds reduce to 0.5m/s in smoke with an optical density of 0.43m (extinction coefficient of 1.0), while in irritant smoke, the walking speed is reduced to 0.4m/s at an optical density of 0.22m/s (extinction coefficient of 0.5).

Hazards by fires


Figure 2.4 The walking speed of volunteers through irritant (solid line) and non-irritant (dashed

line) smoke. The squares indicate the approximate visibility levels, purely according to the extinction coefficient of the smoke.

(2) Toxic gases: The toxic gases produced by fire fall into two main groups, the NARCOTIC GASES - e.g. Carbon Monoxide (CO), Carbon dioxide (CO2), Hydrogen Cyanide (HCN), low Oxygen (O2) and the IRRITANT GASES - e.g. Hydrogen Chloride (HCl), Hydrogen Floride (HF), Hydrogen Bromide (HBr), Sulphur Dioxide (SO2), Oxides of Nitrogen (NOx), Acrolein (CH2 CH CHO). It is estimated that some twenty toxic gases are produced in fires [95]. While popular belief may suggest that heat is the major cause of death in fires, the life threatening capability of these gases claims more fire related fatalities per year. When inhaled, the narcotic gases cause incapacitation and in extreme cases death. These gases attack the central nervous system causing reduced awareness, intoxication and reduced escape capability. Prolonged exposure (several minutes in some cases) causes loss of consciousness and eventually death. Exposure to narcotic fire gases is the main cause of death in building fires. The effect is generally (but not totally) dependent on the dose received rather than the atmospheric concentration. The irritant fire gases cause sensory irritation to the eyes, nose, throat and lungs ranging from mild irritation to severe pain. As the degree of irritancy increases the occupants escape abilities can be severely degraded. The effect is dependent on the concentration of the irritant. If sufficiently high concentrations of irritants are ingested incapacitation and death may result. The effects of some of the major fire gases may be summarised as follows [99]. a) CO: Produced when any combustible material burns incompletely or in reduced oxygen. It is always present in fires and can reach extremely high concentrations. Concentrations of several thousand parts per million (ppm) are not uncommon.

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When CO is inhaled, it is absorbed by the blood from the lungs and combines with haemoglobin to form carboxyhaemoglobin (CoHb). This reaction inhibits the absorption and hence the transport of oxygen to the body tissue. 10 - 20% CoHb generally causes headache, 30 - 40% CoHb generally causes severe headache, nausea, vomiting and collapse, 50 - 100% CoHb generally causes death. However, values as low as 20% are known to have caused death in some victims. It is necessary to consider the original state of health of the victim and their level of activity during exposure. Angina can reduce fatal level dramatically, there is also some evidence to suggest that smoking can also alter the concentrations required to cause the effect. b) HCN: Produced by the combustion of Nitrogen (N) containing materials such as wool, silk, polyurethane foams, nylon, leather, acrylics and some plastics. Levels of 3 mg/lit are normally fatal, however levels as low as 1 mg/lit have resulted in death and people have survived levels as high as 7 mg/lit. An atmospheric concentration of 200 ppm will induce rapid collapse and death. One important difference between the impact of CO and HCN is the so-called knock down; effect that HCN possesses. The impact of CO follows Habers Rule, which assumes that the impact of time and concentration is equivalent. HCN, however, does not follow this relationship, with low concentrations producing relatively long incapacitation times (in the order of tens of minutes) whilst at higher concentrations (approaching only 200ppm), incapacitation occurs in under a minute. c) CO2: Produced by the combustion of any fuel. Effects partially due to exposure concentration and partially dose received. CO2 produces HYPOXIA - a reduction in the amount of oxygen available for tissue respiration. It also has a tendency to increase the respiration rate (breathing rate), thus increasing the rate of uptake of other toxic fire gases and it is itself toxic. 3 - 6% respiratory distress, 6 - 7% dizziness, bordering on loss of consciousness, 7 - 10% loss of consciousness. d) Low O2: All fires will consume O2, if the compartment is not well ventilated the concentration of O2 can drop dramatically. The effects of low O2 hypoxia are partly concentration related and partly dose related. 20.9 - 14.4% slight loss of exercise tolerance, 14.4 - 11.8% reduction in mental task performance, reduced exercise tolerance, 11.8 - 9.6% severe incapacitation, loss of consciousness, 9.6 - 7.8% loss of consciousness, death. e) HF: Produced from fluorinated polymers such as polyvinyl fluoride. Combines with moisture to produce hydrofluoric acid - an extremely potent acid. Causes EDEMA (accumulation of an excessive amount of fluid in cells, tissues or body cavities) within the respiratory tract. Burns produced by hydrofluoric acid cause throbbing pain. 32 ppm Irritation of eyes and nose, 60 ppm Itching of skin, irritation of respiratory tract, 50 - 100 ppm Dangerous to life after a few minutes.

Hazards by fires


f) HCL: Produced from the combustion of PVC and many fire-retardant materials. Combines with water to produce hydrochloric acid which is highly irritant to the eyes, throat and respiratory tract. 35 ppm Irritation of throat, 50 - 100 ppm Barely tolerable, 1000 ppm Danger of edema after a short exposure. g) SO2:

Produced from the combustion of rubbers and other compounds containing sulphur. Combines with water to produce sulphurous acid which is highly irritant to the eyes. It causes uncontrollable coughing.

20 ppm Coughing and eye irritation, 100 - 250 ppm Dangerous to life, 600 - 800 ppm Death in a few minutes. h) CH2 CH CHO: Produced from the combustion of natural materials such as wood and cotton and hydrocarbons such as kerosene. It is an intense eye irritant and causes irritation to the upper respiratory tract. 1 ppm Irritation, 5.5 ppm Intense irritation, 24 ppm Unbearable. All the values presented above are indicative only. Factors such as health, body weight, age, level of activity may affect an individuals tolerance to these products. For the irritant gases, Purser [100] recommends that the levels at which irritant gases are supposed to become severe and influence evacuation capabilities are shown in Table 2.1. These values would be subject to wide variations in the subject population, according to differences in the constitutions of those involved. As well as causing incapacitation, the elevated exposure levels would also slow down the progress of the evacuee due to the increasingly uncomfortable conditions (as well as the effect of these gases on the visual acuity of the evacuees making navigation increasingly difficult). Through this reduction in travel speed, the evacuee would in turn be exposed to the irritant environment for a greater period of time.

Concentration [ppm] Toxic Gas Impair half of population

Incapacitation in half of population

HCl 200 900 HBr 200 900 HF 200 900 SO2 24 120 NO2 70 350 Acrolein 4 20 HCHO 6 30

Table 2.1: Concentration levels of irritant gases resulting in evacuation limiting behaviour.

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(3) Heat: Fires release large amounts of energy, this energy is used to heat up the surrounding environment. Air temperatures in excess of 1000oC can be generated in fully developed enclosure fires. Excessive heat transfer to the skin of exposed people can cause pain and burns. These in turn can result in incapacitation and death. When a victim is attempting to escape a fire they are most likely to be affected by both convective and radiative heat. The rate of convective heat transfer from hot air is dependent on the air temperature, degree of insulation provided by clothing and the humidity in the air. Above 120oC the exposed areas of the skin are subject to burning by convective heat. High levels of humidity compound the problem (reduce the critical temperature) by reducing the cooling effects due to perspiration. Furthermore, humid air delivers more heat to the skin due to waters higher heat capacity. Damage to the respiratory tract due to burns is strongly dependent on the humidity of the air. However, due to its higher heat capacity, inhaled hot air with a high water vapour content can cause more severe damage to the respiratory tract than dry air at the same temperature [95]. Dry air at 300oC can cause burns to the larynx after a few minutes while humid air at 100oC can cause burn throughout the respiratory tract. Of greater concern is the impact of thermal radiation. The so-called pain threshold due to exposure to thermal radiation is the equivalent to a thermal radiation exposure of 2.5 kW/m2 for 24 seconds. This is a conservative value and is the value recommended by Purser [96]. The rationale for using this as a critical tolerance value is that the individual has received a cumulative dose of thermal radiation equivalent to that required to cause the onset of pain (but not burns) and as a result is rendered incapable of continuing to evacuate effectively. An arguably more representative formulation is the so-called incapacitation threshold. This is equivalent to an exposure of 8.25 kW/m2 for one minute. A cumulative dose of radiation equivalent to 8.6 kW/m2 for one minute is expected to cause mortality in 1% of the population [97]. The rationale for using this as the critical tolerance value is that the occupant has received a severe cumulative dose of thermal radiation and is thus likely to be suffering from second degree burns to exposed skin resulting in severe pain and thus will find it difficult to continue to evacuate. To compare the impact of the two formulations, consider an individual exposed to a constant radiative heat flux of approximately 2.5 kW/m2. An exposure to 2.5 kW/m2 for 24 seconds is the recommended tolerance time according to Purser [96]. According to Hymes et al [97] an exposure to 2.6 kW/m2 for 1 minute is the lower limit threshold for second degree blistering of exposed skin, an exposure to 2.6 kW/m2 for 5 minutes can result in a 1% mortality and an exposure to 2.8 kW/m2 for 5 minutes is the lower limit for second degree plus burns (>0.1mm deep) to exposed skin. Using the pain threshold approach, an occupant exposed to 2.5 kW/m2 for 24 seconds is considered incapable of evacuating. Using the incapacitation approach, this value increase so that an individual exposed to 2.5 kW/m2 for 5 minutes is considered incapable of evacuating. The first approach therefore assumes that the evacuee will succumb once a pain threshold is reached; the evacuee subsequently succumbing at a far lower level of radiative flux.

Hazards by fires


Both approaches are subjective and depend on many variables such as age of the occupant, state of health, amount and type of clothing worn, amount of skin exposed etc. For an average adult, if the head, neck and hands are exposed, this is the equivalent of about 14% of the body surface area. If arms and legs are also exposed, this increases the exposed surface area to approximately 61%. The old are more susceptible to burn injuries than the young. The predicted mortality rate from burns as a function of % area burned and age suggests that a 20 year old with 20% area burned has a 1% chance of death which increases to 5% at age 40 and 31% at age 70. For 65% area burned, the chance of death is 67%, 90% and 99% for 20, 40 and 70 year olds respectively [98]. As a result these values are only intended to be indicative. In reality, the degree of thermal radiation a person is subjected to is likely to influence the persons behaviour as well as their physical ability to evacuate. For instance, during a fire evacuation scenario, a person may be less likely to elect to enter an environment in which they will receive a moderately high dose of thermal radiation (e.g. that required to cause the onset of pain). Faced with such a situation, the person may be more likely to select an alternative exit route if one exists or remain in a place of relative safety. However, if the person is already exposed to the fire environment and is in the process of evacuating, they are likely to tolerate higher exposures to thermal radiation than those required to cause pain before they are rendered incapable of evacuating. Thus for tunnel fire environments, it is likely that the higher value is the more reasonable to use. Many of the above principles are applied in a range of toxicity models commonly used in engineering design known as Fractional Effective Dose (i.e. FED) models [100]. These FED models can then be imbedded into advanced evacuation modelling tools to provide an indication of the possible effect of the fire atmosphere on the evacuating population [182-186, 190].

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Design Fire for Road Tunnels


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CHAPTER 3 : EXISTING STANDARDS AND PROPOSALS ON DESIGN FIRES

3.1 Design Fires for Road Tunnels 3.1.1 The Course of some real Fires in Road Tunnels As an introduction to the development of design fires, examples from real tunnel fires are presented: (1) Nihonzaka Tunnel, Japan (1979) (2) Caldecott Tunnel, Oakland, California (1982) (3) Pfnder Tunnel, Austria (1995) (4) Gotthard Tunnel, Switzerland (1997) (5) Mont Blanc Tunnel, France/Italy (1999) (6) Tauern Tunnel, Austria (1999) More fire incidents are included, for example, in the reports about the European UPTUN and NEDIES project as well as in [3, 74]. The data provided for each tunnel is mostly presented in the same logical manner with sections on: (1) Fire Event (2) Course of the fire and extinguishing and rescue work (3) Fire Damage (4) Summary 3.1.1.1. Nihonzaka Tunnel, Japan (1979) (1) Fire Event [2 to 6] The Nihonzaka tunnel is located half way between the cities of Tokyo and Nagoya. The tunnel consists of two approx. 2 km-long tubes which are operated in each direction. There were no restrictions on hazardous materials travelling through the tunnel until the fire occurred. The fire was started on July 11, 1979, by a rear-end collision involving 4 lorries and 2 cars. The accident caused tanks on the vehicles to become leaky so that fuel (petrol and diesel) leaked out. This fuel ignited and thereby triggered a conflagration affecting 173 vehicles in total. Among the burnt-out vehicles there were two road tankers carrying neoprene and accompanying solvent. The load on another lorry involved in the accident consisted of 10 drums of ether. These also became leaky as a result of the accident. The ether which leaked out immediately began to burn intensely. Other materials which burnt were artificial resin and plastics. The deluge sprinklers located in the tunnel were set off automatically by fire alarm systems. After approx. 10 minutes the fire appeared to have been extinguished. However, approx. 15 minutes later the fire flared up again. This produced thick black smoke. Thereafter the fire grew to a length of more than 1100 meters. Although there was a message at the portal of the tunnel that there had been an accident, vehicles continued to drive into the tunnel. A tailback of 231 vehicles formed in front of the seat of the fire.

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(2) Course of the Fire and Extinguishing and Rescue Work [2 to 6] The Nihonzaka tunnel is monitored from two control centres (Shizuoka and Kawasaki). The fire was first noticed by the Kawasaki control room. Mistakenly, from here the fire service responsible for the Shizuoka district was alarmed initially, although it was further away. A unit of the fire service which was much closer was only informed 40 minutes after the fire broke out. The people inside the tunnel initially tried to extinguish it themselves by rolling out the hoses attached to the hydrants in the emergency areas. However they were not able to activate the extinguishing water supply, as they were not aware that in addition to the throwing of a lever - which is normally sufficient - it was also necessary to press a button. Personnel located in the Shizuoka control centre failed in their attempts to reach the scene of the accident, but were able to assist 42 vehicles in escaping from the tunnel. At around 8.30 pm 208 people had managed to escape from the tunnel on foot (approx. 15 minutes after the fire had broken out again). The firemen reaching the scene of the fire could not initially achieve a great deal, as their respiratory equipment only allowed each of them to work for 30 minutes. The supply of fire-fighting water in the tunnel (approx. 170 m) had been used up approximately 1 hours after the fire started without it being possible to put the fire out. When the fire-fighting water ceased to flow, combustible gases and vapours drifted from the source of the fire to two groups of vehicles in the tunnel, setting them alight. The extinguishing work could only be resumed after a "shuttle service" to surface waters had been set up using 7 sets of fire-fighting appliances. It was only possible to bring the fire under control 2 days after it had broken out. The fire, which initially started on July 11, 1979, was finally extinguished on July 18 (i.e. approx. one week after the rear-end collision). During the fire the semi-cross ventilation of the tunnel worked in the suction mode at full power. However this was not sufficient to extract enough smoke and hot burning gases for the fire service units, who were equipped only with limited respiratory protection, to effectively fight the fire. (3) Fire Damage [2 to 6] Of the 230 vehicles in the tunnel, 173 were destroyed by the fire. 7 people died in the fire, while a further 2 were injured. The tunnel lining and the additional 4.5 mm-thick reinforcement of the tunnel walls were damaged for a length of approx. 1,100 meters. The greatest damage occurred in an area of approx. 500 metres on either side of the seat of the fire. The road surface melted in places up to a depth of 2-3 cm on average, with the maximum depth being approx. 7 cm. Electric cables and pipes laid in a cable duct in the road surface concrete continued to function normally. During the repair work the concrete of the tunnel lining was removed up to a depth of approx. 3 cm. Then wire grating was placed in position and steel fibre concrete injected using the dry injection method. The application thickness depended on the damage to the tunnel, being approx. 5-10 cm on average. After the repair work to the roadway had been completed on August 7, work began on repairing the tunnel equipment. This work lasted approx. 1 month, including among other things: a) renewal of the surveillance and fire alarm systems b) reconstruction of the ventilation system c) renewal and supplementation of the fire extinguishing equipment d) installation of a guided escape system (including loudspeakers)



(4) Summary a) The fire was caused by a rear-end collision. b) The fire brigade alarm was incorrect (wrong fire brigade, too late). c) Those people in the tunnel could not use the fire extinguishers as the instructions were

not clear. d) The efforts of the fire brigade to extinguish the fire were considerably hampered by the

inadequate respiratory protection devices. e) The suction power of the semi-cross ventilation system in the tunnel was not sufficient to

extract the smoke and hot burning gases. f) The hot burning gases caused the fire to jump between groups of vehicles. g) In the fire 7 people died, the tunnel was damaged over a length of approx. 1,100 meters

and 173 vehicles were destroyed. 3.1.1.2 Caldecott Tunnel, Oakland, California (1982) (1) Fire Event [2, 3] The fire occurred on April 7, 1982, shortly before midnight, with very little traffic in the tunnel. A drunken car driver lost control of his car and collided several times with the wall of the tunnel. Behind a right-hand curve in the tunnel he stopped in the left-hand lane in order to inspect the damage he had caused. Two or three cars then passed the stationary vehicle without there being an accident. However, an empty bus then pulled out to overtake a full petrol tanker without noticing the stationary car in the left-hand lane. When the towing vehicle of the petrol tanker was level with the stationary car all three vehicles collided. The bus driver was thrown out of the bus by the force of the collision. The bus itself carried on without the driver and smashed into a concrete pillar outside the tunnel. This alerted the personnel operating the tunnel to the accident inside the tunnel. The tanker was carrying a total of 33,300 litres of petrol, of which 20,400 litres were in the trailer, which was torn open by the collision. The petrol leaked out and ignited. As there were no traffic lights at the entrance to the tunnel, vehicles continued to drive into the tunnel even after the fire had broken out. Some of these drove into the area affected by the fire, with the result that in total 2 lorries and 4 cars burnt out. (2) Course of the Fire and Extinguishing and Rescue Work [2, 3] The tunnel personnel initially tried to find out what was going on in the tunnel. However it took approx. 7 minutes until the fire brigade was alarmed. The first fire service units reached the western portal of the tunnel approx. 11 minutes after the vehicles collided. Fire units did not reach the eastern portal until approx. 19 minutes after the accident occurred. The ventilation in the tunnel switched itself off at this time. From then on, the course the fire took was influenced by the natural ventilation. Within three minutes of the collision the tunnel filled with over 150C hot smoke between the eastern portal and the burning tanker. As the escape routes to the neighbouring tubes were not particularly well marked they were not noticed by the people in the tunnel. They remained with their cars and were enclosed by the smoke. Some of the vehicles which drove into the tunnel after the fire had started reversed back out of the tunnel. As the natural air current drove the burning gases to the eastern portal, it was possible for the firemen on the opposite side of the fire to get within 25 meters of the fire. At this time, however, they did not make any effort to extinguish the fire. When they wanted to operate a valve in order to keep the water and petrol mixture in the tunnel drainage system away from a local lake they discovered that this valve was corroded and could not be moved.



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When approx. 75 minutes after the collision the first efforts were made to extinguish the fire, the water pressure dropped and the extinguishing water supply in the tunnel failed. This may have been attributable to the damaged fire-fighting water connections in the vicinity of the burning tanker, as some firemen noticed that water was leaking out of the damaged connections. The residual fire was finally extinguished with foam extinguishing agents and extinguishing powder. After approx. 2 hours (after the time of the collision) the fire was finally under control. (3) Fire Damage [2, 3] The tunnel and tunnel equipment, as well as the road surface, were badly damaged over a length of approx. 580 meters. The repair costs amounted to more than approx. 3.3 million EUR (3 million US dollars). (4) Summary a) The fire was triggered by a drunken car driver who caused a rear-end collision (bus, petrol tanker) in the tunnel. b) The tunnel was filled with smoke within approx. 3 minutes. c) As it was not possible to stop vehicles entering the tunnel, more people were placed in danger by the fire. d) Escape routes to the neighbouring tubes were not used owing to inadequate marking in conjunction with the dense smoke. e) The fire-fighting water supply pipes in the tunnel were damaged by the impact of the vehicle (no impact protection). f) Foam extinguishing agents and extinguishing powder proved an advantage in extinguishing the fire. 3.1.1.3 Pfnder Tunnel, Austria (1995) (1) Fire Event [7, 8] On April 10, 1995, there was a traffic accident in the tunnel as a result of which three vehicles burnt out. The fire was located approx. 4.3 km from the northern portal and 2.4 km from the southern portal. The accident was caused by the microsleep of a car driver travelling in a southerly direction. He crossed over to the oncoming traffic lane and crashed into an articulated vehicle laden with bread. This lorry began to skid, then also crossed over to the wrong side of the road, slid along the tunnel wall for approx. 130 meters and then finally crashed into an oncoming minibus with caravan carrying three people. The minibus caught fire immediately and then set the articulated lorry and a following car on fire. (2) Course of the Fire and Extinguishing and Rescue Work [7, 8] In the tunnel control room the computer-controlled fire programme was started immediately. Furthermore, the alarm was passed on to the local municipal police force and the rescue services in the town of Bregenz. From here, the fire brigade responsible for the southern portal was alarmed at 8.45, and at 8.47 the fire service responsible for the northern portal. At 8.48 control of operations at the southern portal was taken over by the fire brigade at the tunnel control centre. While the alarms were being given, an explosive flare-up was observed on the monitors in the tunnel control centre. The scene of the accident was filled with smoke within seconds so that it was no longer possible to follow the course of the fire on the screens in the control centre.



The volunteer fire service of the town of Bregenz entered the tunnel at around 8.57 am from both portals without having any exact information on the situation at the seat of the fire. Some minutes later four people fleeing in the direction of the southern cavern of the tunnel were rescued (the car driver causing the accident, the driver of the articulated lorry involved in the accident and two lorry drivers who had driven into the danger area from the southern side). These people and the rescue teams were caught up in the smoke which was drifting in a southerly direction. From the scene of the accident the tunnel was completely filled with smoke in a northerly direction for approx. 270 meters and in a southerly direction for approx. 800 meters. In spite of the excessive amount of smoke and the detonations which could be heard in the tunnel, four firemen attempted to reach the scene of the fire with a special fire engine equipped for tunnel use. This was intended to prevent any injured people who might be lying on the ground from being driven over in the dark by an emergency vehicle. The driver of the fire engine was only able to find his way in the tunnel by skirting the edge of the pavement with his tyres in order not to lose his bearings. As the visibility was zero because of the dense smoke, the firemen could not find the central line of the road even when they bent down or crawled along the ground. A fireman walking in front of the fire engine collided with a parked lorry in the smoke because he was not able to see the obstacle in good time. Moreover, owing to the very poor visibility it was extremely difficult to drive the fire engine between the lorries and cars standing in the traffic jam in the tunnel. In order to be able to finally begin extinguishing the fire, it was initially necessary in the smoke-filled tunnel for the firemen to identify by touch a fire extinguishing bay from where they could open a water valve located in front of a hydrant. The extinguishing work was also greatly hindered by the heat at the scene of the fire. Nevertheless, the fire was under control approx. 1 hour after the fire brigades had been alarmed. Coordination of the fire-fighting measures was also greatly hindered by the fact that the two-way radio system in the tunnel stopped working. The three occupants of the minibus were burned to death in their vehicle. All the other people (at the time of the accident there were approx. 60 people in vehicles in the tunnel) were able to escape from the tunnel unharmed. (3) Fire Damage [7, 8] The articulated lorry, a car and a minibus were written off by the fire. The tunnel ceiling at the scene of the fire showed spalling and cracks. Even the supporting consoles of the false ceiling on the internal vault were weakened by the heat of the fire. This structural damage stretched over a length of approx. 24 meters. Additionally, the tunnel was completely blackened by soot over a length of 35 meters north of the scene of the accident, and 70 meters in a southerly direction. The operating equipment, such as the tunnel lighting, the aerial cables for the tunnel radio and the supply lines in a cable duct on the tunnel ceiling, was damaged over a length of approx. 360 meters. In order that the tunnel could be put back into temporary operation, the false ceiling was initially supported with thick wooden poles and planks. In addition, a narrow-meshed steel net was fixed in place on the ceiling in the damaged part of the tunnel. After approx. 2 days it was possible to open the tunnel again for traffic. The final repair work was carried out in May 1995. The cost of this work was estimated to be approx. 200.000,- EUR.



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(4) Summary a) Overtired drivers are a considerable danger to other road users. b) The extinguishing work was hindered by smoke, heat and the fact that the two-way radio connections did not work. c) Dense smoke spread out over several hundred meters across the entire cross-section of the tunnel. d) Owing to the dense smoke it was not possible to follow the course of the fire on the video monitoring system. 3.1.1.4 Gotthard Tunnel, Switzerland (1997) (1) Fire Event [9] On October 31, 1997, a car transporter caught fire in the tunnel. The transporter was laden with 8 new cars. After noticing the fire, the driver stopped approx. 1 km before the exit portal and called for help via the nearest emergency telephone. The automatic fire alarm system of the tunnel registered the fire approx. 1 minute after the emergency call made by the lorry driver. When the fire broke out there were 60 vehicles, including 20 lorries, in the tunnel. Approximately half of these vehicles were driving in the direction of the fire and therefore had to be stopped. From measurement data of the tunnel surveillance system and information provided by the emergency services it was possible after the fire to estimate the maximum energy release rate of the fire at approx. 22 MW. (2) Course of the Fire and Extinguishing and Rescue Work [9] The fire alarm was received by the tunnel control centre at 7.21 am. Approx. 1 minute later all emergency systems were activated, some automatically and some by hand. Four minutes after the alarm the tunnel fire service entered the tunnel from the southern portal, the portal located nearest to the fire. The tunnel fire service responsible for the northern portal drove into the tunnel 9 minutes after the alarm was raised. First aid workers were already in the tunnel 3 minutes after the emergency call, dealing mainly with the vehicles which had formed a tailback. They instructed the car drivers to turn around and drive out of the tunnel. Only a few of the lorry drivers went to the emergency rooms located in the tunnel without first being requested to do so. Most of the drivers did not want to leave their vehicles in spite of the immediate danger presented by the smoke. As a rule the vehicle occupants had to be requested to leave their vehicles by the emergency services, as well as having to be accompanied by them to the nearest emergency rooms. In total, 60 people were taken to the emergency rooms. Only one person suffered from smoke inhalation. At the scene of the fire the emergency services were placed in danger by concrete spalling. Furthermore, it was difficult to estimate the remaining strength of the damaged false ceiling. This was exacerbated by the fact that the false ceiling was scarcely visible owing to the dense smoke. The rescue was made easier by the relatively slow development of the fire and the slow rate at which the smoke spread. Approximately 1 hour after the start of the fire it was under control, before being completely extinguished after a further 30 minutes. Subsequently, however, the wreck of the vehicle had to be cooled down for approximately a further 2 hours.



(3) Fire Damage [9] The spalling of the false ceiling stretched over an area of approx. 90 m to 100 m. The spalling reached down as far as the reinforcing steel. The vertical deformation of the false ceiling was up to approx. 10 cm. Subsequent laboratory analyses showed that the strength of the ceiling sections had dropped owing to the effects of the high temperatures of the fire and the water used to extinguish the fire to approx. 50% of the values for new ceiling sections. The damage to the tunnel equipment was also extensive. Through the effects of the smoke, the temperature being about 700C, and the direct effects of the fire, video cameras, aerial cables, communication cables, lighting equipment, traffic signs and an emergency telephone were damaged. The false ceiling and its reinforcement outside the direct location of the fire were heated up to approx. 500C by the smoke from the fire. The repair work began immediately after the fire had been extinguished and was carried out at the same time as the tunnel was being cleared (removal of the wrecked vehicle, turning around and driving out the lorries jammed in the tunnel). Such measures were taken immediately with the intention of reopening the tunnel as quickly as possible. They had already been completed approx. 13 hours after the fire started. The immediate measures included removal of the damaged electrical installations over a length of approx. 100 meters and the installation of emergency lighting,

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