Fire hazard testing - Part 6-1: Smoke obscuration - General guidance

Gives guidance on: a) optical measurement of smoke obscuration; b) general aspects of optical smoke test methods; c) consideration of test methods; d) expression of smoke test data; e) relevance of optical smoke data to hazard assessment. The main changes with respect to the previous edition are listed below: - Modified title. - Updated normative references. - Expanded terms and definitions. - Numerous editorial changes of a technical nature throughout the publication. - A flowchart has been added for the evaluation and consideration of smoke test methods. Has the status of a basic safety publication in accordance with IEC Guide 104

Prüfungen zur Beurteilung der Brandgefahr - Teil 6-1: Sichtminderung durch Racuh - Allgemeiner Leitfaden

Essais relatifs aux risques du feu - Partie 6-1: Opacité des fumées - Lignes directrices générales

Fournit des lignes directrices sur: a) la mesure optique de l'obscurcissement par la fumée; b) les aspects généraux des méthodes d'essais optiques de la fumée; c) des considérations concernant les méthodes d'essais; d) l'expression des résultats d'essais; e) la pertinence des résultats des mesures optiques de la fumée pour l'évaluation des risques. Les principales modifications par rapport à l'édition antérieure sont indiquées ci-dessous: - Titre modifié. - Mise à jour des références normatives. - Ajout de termes et de définitions. - Nombreuses modifications rédactionnelles de nature technique dans toute la publication. - Ajout d'un logigramme pour l'évaluation et la considération des méthodes d'essais de fumée. A le statut de publication fondamentale de sécurité, conformément au Guide CEI 104

Preskušanje požarne ogroženosti - 6-1. del: Otemnitev dima - Splošna navodila (IEC 60695-6-1:2005)

Ta del IEC 60695 podaja navodila o:
a) optičnih meritvah otemnitve dima;
b) splošnih vidikih optičnih dimnih preskusnih metod;
c) obravnavi preskusnih metod;
d) izražanju podatkov dimnih preskusov;
e) pomembnosti optičnih dimnih podatkov za oceno ogroženosti.
Ena od odgovornosti tehničnega odbora je, če je primerno, da uporabi temeljne varnostne publikacije pri pripravi svojih publikacij.

General Information

Status
Published
Publication Date
15-Jun-2005
Drafting Committee
Parallel Committee
Current Stage
6060 - Document made available
Due Date
16-Jun-2005
Completion Date
16-Jun-2005

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SIST EN 60695-6-1:2005SLOVENSKIseptember 2005

STANDARDPreskušanje požarne ogroženosti – 6-1. del: Otemnitev dima – Splošna navodila (IEC 60695-6-1:2005)Fire hazard testing – Part 6-1: Smoke obscuration – General guidance (IEC 60695-6-1:2005)©

Standard je založil in izdal Slovenski inštitut za standardizacijo. Razmnoževanje ali kopiranje celote ali delov tega dokumenta ni dovoljenoReferenčna številkaSIST EN 60695-6-1:2005(en)ICS13.220.40; 29.020

EUROPEAN STANDARD
EN 60695-6-1 NORME EUROPÉENNE EUROPÄISCHE NORM

June 2005 CENELEC European Committee for Electrotechnical Standardization Comité Européen de Normalisation Electrotechnique Europäisches Komitee für Elektrotechnische Normung

Central Secretariat: rue de Stassart 35, B - 1050 Brussels

© 2005 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.

Ref. No. EN 60695-6-1:2005 E
ICS 13.220.99; 29.020 Supersedes EN 60695-6-1:2001
English version
Fire hazard testing Part 6-1: Smoke obscuration –
General guidance (IEC 60695-6-1:2005)
Essais relatifs aux risques du feu Partie 6-1: Opacité des fumées –
Lignes directrices générales (CEI 60695-6-1:2005)
Prüfungen zur Beurteilung

der Brandgefahr Teil 6-1: Sichtminderung durch Rauch - Allgemeiner Leitfaden (IEC 60695-6-1:2005)

This European Standard was approved by CENELEC on 2005-05-01. CENELEC members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration.

Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the Central Secretariat or to any CENELEC member.

This European Standard exists in three official versions (English, French, German). A version in any other language made by translation under the responsibility of a CENELEC member into its own language and notified to the Central Secretariat has the same status as the official versions.

CENELEC members are the national electrotechnical committees of Austria, Belgium, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.

EN 60695-6-1:2005 - 2 - Foreword The text of document 89/692/FDIS, future edition 2 of IEC 60695-6-1, prepared by IEC TC 89, Fire hazard testing, was submitted to the IEC-CENELEC parallel vote and was approved by CENELEC as EN 60695-6-1 on 2005-05-01. This European Standard supersedes EN 60695-6-1:2001. The main changes with respect to EN 60695-6-1:2001 are: – modified title; – updated normative references; – expanded terms and definitions; – numerous editorial changes of a technical nature throughout the publication; – a flowchart has been added for the evaluation and consideration of smoke test methods. This European Standard is to be used in conjunction with IEC/TS 60695-6-2. The following dates were fixed: – latest date by which the EN has to be implemented

at national level by publication of an identical
national standard or by endorsement
(dop)
2006-02-01 – latest date by which the national standards conflicting
with the EN have to be withdrawn
(dow)

2008-05-01 Annex ZA has been added by CENELEC. __________ Endorsement notice The text of the International Standard IEC 60695-6-1:2005 was approved by CENELEC as a European Standard without any modification. __________

- 3 - EN 60695-6-1:2005
Annex ZA
(normative)
Normative references to international publications

with their corresponding European publications The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. NOTE Where an international publication has been modified by common modifications, indicated by (mod), the relevant EN/HD applies. Publication Year Title EN/HD Year IEC 60695-1-1 - 1) Fire hazard testing Part 1-1: Guidance for assessing the fire hazard of electrotechnical products - General guidelines

EN 60695-1-1 2000 2) IEC 60695-4 1993 Part 4: Terminology concerning fire tests EN 60695-4 1995 A1 1995

- - A2 2001

- - IEC 60695-6-2 2001 Part 6-2: Smoke obscuration - Summary and relevance of test methods

- - IEC 60695-6-30 - 1) Part 6: Guidance and test methods on the assessment of obscuration hazard of vision caused by smoke opacity from electrotechnical products involved in fires - Section 30: Small-scale static method - Determination of smoke opacity - Description of the apparatus

- - IEC 60695-6-31 - 1) Part 6-31: Smoke obscuration - Small-scale static test - Materials

- - IEC Guide 104 1997 The preparation of safety publications and the use of basic safety publications and group safety publications

- - ISO/TR 9122-1 1989 Toxicity testing of fire effluents Part 1: General

- - ISO 5659-2 1994 Plastics - Smoke generation Part 2: Determination of capital density by a single-chamber test

EN ISO 5659-2 1998 ISO 13943 2000 Fire safety - Vocabulary

EN ISO 13943 2000 ISO/IEC Guide 51 1999 Safety aspects - Guidelines for their inclusion in standards - -

1) Undated reference. 2) Valid edition at date of issue.

NORME INTERNATIONALECEIIECINTERNATIONALSTANDARD 60695-6-1Deuxième éditionSecond edition2005-05Essais relatifs aux risques du feu – Partie 6-1: Opacité des fumées – Lignes directrices générales Fire hazard testing – Part 6-1: Smoke obscuration – General guidance Pour prix, voir catalogue en vigueur For price, see current catalogue© IEC 2005

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Copyright - all rights reservedAucune partie de cette publication ne peut être reproduite ni utilisée sous quelque forme que ce soit et par aucun procédé, électronique ou mécanique, y compris la photocopie et les microfilms, sans l'accord écrit de l'éditeur. No part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from the publisher. International Electrotechnical Commission,

3, rue de Varembé, PO Box 131, CH-1211 Geneva 20, SwitzerlandTelephone: +41 22 919 02 11 Telefax: +41 22 919 03 00 E-mail: inmail@iec.ch

Web: www.iec.ch CODE PRIX PRICE CODE VCommission Electrotechnique InternationaleInternational Electrotechnical CommissionPUBLICATION FONDAMENTALE DE SÉCURITÉ

BASIC SAFETY PUBLICATION

60695-6-1 ¤ IEC:2005 – 3 – CONTENTS FOREWORD...........................................................................................................................7INTRODUCTION...................................................................................................................111Scope.............................................................................................................................132Normative references......................................................................................................133Terms, definitions and symbols.......................................................................................153.1Terms and definitions............................................................................................153.2Symbols................................................................................................................214General aspects of smoke test methods..........................................................................234.1Fire scenarios and fire models...............................................................................234.2Factors affecting smoke production........................................................................275Principles of smoke measurement...................................................................................295.1Bouguer’s law........................................................................................................295.2Extinction area.......................................................................................................315.3Log10 units............................................................................................................335.4Light sources.........................................................................................................335.5Specific extinction area..........................................................................................335.6Mass optical density..............................................................................................355.7Visibility.................................................................................................................376Static and dynamic methods...........................................................................................376.1Static methods.......................................................................................................376.2Dynamic methods..................................................................................................377Test methods..................................................................................................................417.1Consideration of test methods................................................................................417.2Selection of test specimen.....................................................................................418Presentation of data........................................................................................................419Relevance of data to hazard assessment........................................................................43Annex A (informative)

Calculation of visibility........................................................................47Annex B (informative)

Relationships between Ds and some other smoke parameters as measured in IEC 60695-6-30 and IEC 60695-6-31.................................................................51Annex C (informative)

Relationships between percent transmission, as measured in a "three metre cube" enclosure, and extinction area.................................................................57Bibliography..........................................................................................................................61Figure 1 – Chart of different phases in the development of a fire within a compartment..........25Figure 2 – Attenuation of light by smoke................................................................................31Figure 3 – Extinction area.....................................................................................................31Figure 4 – Dynamic smoke measurement..............................................................................39Figure 5 – Evaluation and consideration of smoke test methods............................................45

60695-6-1¤ IEC:2005 – 5 – Figure A.1 – Visibility (Z) versus extinction coefficient (k)....................................................47Figure B.1 – Smoke parameters related to Dsas measured in IEC 60695-6-30 and IEC 60695-6-31..................................................................................................................55Figure C.1 – Extinction area (amount of smoke) related to percent transmission as measured in the "three metre cube"....................................................................................59Table 1 – General classification of fires (ISO/TR 9122-1)....................................................25Table B.1 – Conversion from Ds to some other smoke parameters as measured in IEC 60695-6-30 and IEC 60695-6-31..................................................................................53Table C.1 – Conversions from percent transmission, as measured

in the “three metre cube” to amount of smoke (extinction area).........................................................................57

60695-6-1 ¤ IEC:2005 – 7 – INTERNATIONAL ELECTROTECHNICAL COMMISSION ____________FIRE HAZARD TESTING –Part 6-1: Smoke obscuration –

General guidance FOREWORD 1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising all national electrotechnical committees (IEC National Committees). The object of IEC is to promote international co-operation on all questions concerning standardization in the electrical and electronic fields. To this end and in addition to other activities, IEC publishes International Standards, Technical Specifications, Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested in the subject dealt with may participate in this preparatory work. International, governmental and non-governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely with the International Organization for Standardization (ISO) in accordance with conditions determined by agreement between the two organizations. 2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international consensus of opinion on the relevant subjects since each technical committee has representation from all interested IEC National Committees.

3) IEC Publications have the form of recommendations for international use and are accepted by IEC National Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any misinterpretation by any end user. 4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications transparently to the maximum extent possible in their national and regional publications. Any divergence between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in the latter. 5) IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any equipment declared to be in conformity with an IEC Publication. 6) All users should ensure that they have the latest edition of this publication. 7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and members of its technical committees and IEC National Committees for any personal injury, property damage or other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC Publications.

8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is indispensable for the correct application of this publication. 9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of patent rights. IEC shall not be held responsible for identifying any or all such patent rights. International Standard IEC 60695-6-1 has been prepared by IEC technical committee 89: Fire hazard testing. This second edition cancels and replaces the first edition of IEC 60695-6-1 published in 2001. It constitutes a technical revision. The main changes with respect to the previous edition are listed below: – Modified title. – Updated normative references. – Expanded terms and definitions. – Numerous editorial changes of a technical nature throughout the publication. – A flowchart has been added for the evaluation and consideration of smoke test methods.

60695-6-1 ¤ IEC:2005 – 9 – It has the status of a basic safety publication in accordance with IEC Guide 104 and ISO/IEC Guide 51. The text of this standard is based on the following documents: FDIS Report on voting 89/692/FDIS 89/696/RVD Full information on the voting for the approval of this standard can be found in the report on voting indicated in the above table. This standard is to be used in conjunction with IEC 60695-6-2. This publication has been drafted in accordance with the ISO/IEC Directives, Part 2. The IEC 60695-6 series, under the general heading Fire hazard testing, consists of the following parts Part 6-1:

Smoke obscuration – General guidance Part 6-2:
Smoke obscuration –Summary and relevance of test methods Part 6-30:

Smoke obscuration – Guidance and test methods on the assessment of obscuration hazard of vision caused by smoke opacity from electrotechnical products involved in fires – Small scale static method - Determination of smoke opacity - Description of the apparatus Part 6-31:

Smoke obscuration – Small-scale static test – Materials The committee has decided that the contents of this publication will remain unchanged until the maintenance result date indicated on the IEC web site under "http://webstore.iec.ch" in the data related to the specific publication. At this date, the publication will be

• reconfirmed, • withdrawn, • replaced by a revised edition, or • amended.

60695-6-1 ¤ IEC:2005 – 11 – INTRODUCTION The risk of fire needs to be considered in any electrical circuit, and the objective of component, circuit and equipment design, as well as the choice of material, is to reduce the likelihood of fire, even in the event of foreseeable abnormal use, malfunction or failure. Electrotechnical products, primarily victims of a fire, may nevertheless contribute to the fire. One of the contributing hazards is the release of smoke, which may cause loss of vision and/or disorientation which could impede escape from the building or fire fighting. Smoke particles reduce the visibility due to light absorption and scattering. Consequently, people may experience difficulties in finding exit signs, doors and windows. Visibility is often determined as the distance at which an object is no longer visible. It depends on many factors, but close relationships have been established between visibility and the measurements of the extinction coefficient of smoke – see Annex A. The production of smoke and its optical properties can be measured as well as other fire properties, such as heat release, flame spread, and the production of toxic gas and corrosive effluent. This part of IEC 60695-6 serves as a guidance document and focuses on obscuration of light by smoke.

60695-6-1 ¤ IEC:2005 – 13 – FIRE HAZARD TESTING – Part 6-1: Smoke obscuration –

General guidance 1 Scope This part of IEC 60695 gives guidance on: a) optical measurement of smoke obscuration; b) general aspects of optical smoke test methods; c) consideration of test methods; d) expression of smoke test data; e) relevance of optical smoke data to hazard assessment. One of the responsibilities of a technical committee is, wherever applicable, to make use of basic safety publications in the preparation of its publications. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. IEC 60695-1-1, Fire hazard testing – Part 1-1: Guidance for assessing the fire hazard of electrotechnical products – General guidelines IEC 60695-4:20011,Fire hazard testing – Part 4: Terminology concerning fire testsIEC 60695-6-2:2001, Fire hazard testing – Part 6-2: Smoke obscuration – Summary and relevance of test methods

IEC 60695-6-30, Fire hazard testing – Part 6: Guidance and test methods on the assessment of obscuration hazard of vision caused by smoke opacity from electrotechnical products involved in fires – Section 30: Small-scale static method – Determination of smoke opacity – Description of the apparatusIEC 60695-6-31, Fire hazard testing – Part 6-31: Smoke obscuration – Small-scale static test – Materials IEC Guide 104:1997, The preparation of safety publications and the use of basic safety publications and group safety publicationsISO/TR 9122-1:1989, Toxicity testing of fire effluents – Part 1: General___________1 Consolidated edition 2.2 (2001) that includes IEC 60695-4 (1993), its amendment 1 (1995) and its amendment 2 (2001).

60695-6-1 ¤ IEC:2005 – 15 – ISO 5659-2:1994, Plastics – Smoke generation – Part 2: Determination of optical density by a single-chamber test ISO/IEC 13943:2000, Fire safety – Vocabulary ISO/IEC Guide 51:1999. Safety aspects – Guidelines for inclusion in standards 3 Terms, definitions and symbols 3.1 Terms and definitions

For the purpose of this document, the following terms, definitions and symbols apply.

3.1.1combustion exothermic reaction of a substance with an oxidizer NOTECombustion generally emits effluent accompanied by flames and/or visible light. [ISO/IEC 13943, definition 23] 3.1.2extinction area of smoke product of the extinction coefficient and the volume occupied by the smoke NOTEIt is a measure of the amount of smoke. [IEC 60695-4, definition 2.130] 3.1.3extinction coefficient of smoke natural logarithm of the opacity of smoke divided by the path length of the light used to measure the smoke opacity [IEC 60695-4, definition 2.131] 3.1.4fire a) process of combustion characterized by the emission of heat and effluent accompanied by smoke, and/or flame, and/or glowing; b) rapid combustion spreading uncontrolled in time and space [IEC 60695-4, definition 2.29] 3.1.5fire effluent total gaseous, particulate or aerosol effluent from combustion or pyrolysis [IEC 60695-4, definition 2.33] 3.1.6fire hazard potential for injury or loss of life and/or damage to property by fire [IEC 60695-4, definition 2.36]

60695-6-1 ¤ IEC:2005 – 17 – 3.1.7fire model a laboratory process, including both the apparatus and the mode of operation, intended to simulate a certain stage of a real fire [IEC 60695-4, definition 2.120] 3.1.8fire scenario detailed description of conditions, including environmental, of one or more stages from before ignition to after completion of combustion in an actual fire at a specific location or in a real-scale simulation [ISO/IEC 13943, definition 58] 3.1.9flash-over

the rapid transition to a state of total surface involvement in a fire of combustible materials within an enclosure [IEC 60695-4, definition 2.59] 3.1.10heat flux amount of thermal energy emitted, transmitted or received per unit area and unit time NOTEIt is expressed in watts per square metre.[ISO/IEC 13943, definition 85] 3.1.11ignitioninitiation of combustion NOTE The term "ignition" in French has a very different meaning [state of body combustion]. [ISO/IEC 13943, definition 96] 3.1.12large scale test a test, the size of which exceeds that of a typical laboratory bench test [IEC 60695-4, definition 2.122] 3.1.13mass optical density of smoke optical density multiplied by a factor, V/(L×∆m), where V is the volume of the test chamber, ∆m is the mass loss of the test specimen and L is the light path length [IEC 60695-4, definition 2.133] 3.1.14opacity (of smoke) the ratio (I/T) of incident luminous flux (I) to transmitted luminous flux (T) through smoke, under specified test conditions [IEC 60695-4, definition 2.89]

60695-6-1 ¤ IEC:2005 – 19 – 3.1.15optical density (of smoke) [lg(I/T)]common logarithm of the opacity of smoke (see also specific optical density)[IEC 60695-4, definition 2.90] 3.1.16realscale test a test which simulates an end-use situation in both size and surroundings [IEC 60695-4, definition 2.123] 3.1.17small scale test a test which may be made on a typical laboratory bench [IEC 60695-4, definition 2.124] 3.1.18smoke a visible suspension of solid and/or liquid particles in gases resulting from combustion or pyrolysis [IEC 60695-4, definition 2.101] 3.1.19smoke obscuration the reduction in visibility due to smoke [IEC 60695-4, definition 2.102] 3.1.20smoke production rate extinction area of smoke produced, per unit time, by the combustion of a material under specified test conditions 3.1.21smoke release rate see "smoke production rate" 3.1.22specific extinction area of smoke extinction area of smoke divided by the mass loss of the test specimen [IEC 60695-4, definition 2.137] 3.1.23specific optical density (of smoke) optical density multiplied by a geometric factorV/AL, where V is the volume of the test chamber, A is the exposed surface area of the test specimen and L is the light path length NOTEThe use of the term ‘specific’ does not, in this case, denote 'per unit mass’ but rather denotes a dimensionless quantity associated with a particular test apparatus and exposed surface area of the test specimen. 3.1.24visibility maximum distance at which an object of defined size, brightness and contrast can be seen and recognized

60695-6-1 ¤ IEC:2005 – 21 – 3.2 Symbols Symbol Quantity Typical units Aexposed area of test specimen m2Dlinear decadic absorption coefficient (commonly called optical density per metre) m…1'Doptical density dimensionless Dmassmass optical density m2 kg–1sDspecific optical density dimensionless )(malsomaxDDmaximum specific optical density dimensionless Iintensity of incident light W TI/ratio of incident light to transmitted light dimensionless klinear Napierian absorption coefficient (commonly called extinction coefficient) m–1Llight path length through smoke m m∆mass loss of test specimen kg mmass loss rate kg s–1Ssmoke extinction area (also total smoke) m2Ssmoke production rate (rate of change of extinction area) m2 s–1ttime st∆sampling time interval s Tintensity of transmitted light W Vvolume of chamber m3Vvolume flow rate of smoke m3 s–1fσspecific extinction area m2 kg…1γa constant of proportionality between visibility and extinction coefficient dimensionless ωvisibility mNOTE 1 The quantities based on log10, i.e. D,D′,Dmax,DmassandDs, have similar symbols but they are different quantities and have different units. NOTE 2 The use of the term "specific" in the case of specific optical density, Ds, does not denote "per unit mass".

60695-6-1 ¤ IEC:2005 – 23 – 4 General aspects of smoke test methods 4.1 Fire scenarios and fire models During recent years, major advances have been made in the analysis of fire effluents. It is recognized that the composition of the mixture of combustion products is particularly dependent upon the nature of the combusting materials, the prevailing temperatures and ventilation conditions, especially access of oxygen to the seat of the fire. Table 1 shows how the different stages of a fire relate to the changing atmosphere. Conditions for use in laboratory tests (small or large-scale) can be derived from the table in order to correspond, as far as possible, to real-scale fires. Fire involves a complex and interrelated array of physical and chemical phenomena. As a result, it is difficult to simulate all aspects of a real-scale fire in a smaller scale apparatus. This problem of fire model validity is perhaps the single most perplexing technical problem associated with all fire testing. General guidance for assessing the fire hazard of electrotechnical products is given in IEC 60695-1-1. After ignition, fire development may occur in different ways depending on the environmental conditions, as well as on the physical arrangement of the combustible materials. However, a general pattern can be established for fire development within a compartment, where the general temperature-time curve shows three stages, plus a decay stage (see Figure 1). Stage 1 is the incipient stage of the fire prior to sustained flaming, with little rise in the fire room temperature. Ignition and smoke generation are the main hazards during this stage. Stage 2 (developing fire) starts with ignition and ends with an exponential rise in the fire room temperature. Spread of flame and heat release are the main hazards in addition to smoke during this stage. Stage 3 (fully developed fire) starts when the surface of all of the combustible contents of the room has decomposed to such an extent that sudden ignition occurs all over the room, with a rapid and large increase in temperature (flash-over). At the end of stage 3, the combustibles and/or oxygen have been largely consumed and hence the temperature decreases at a rate which depends on the ventilation and the heat and mass transfer characteristics of the system. This is known as decay. In each of these stages, a different mixture of decomposition products may be formed and this, in turn, influences the smoke density produced during that stage. Moreover, information is required on the fire scenario being considered, in particular the conditions of incident heat flux, oxygen availability and smoke-venting facilities.

60695-6-1 ¤ IEC:2005 – 25 – Table 1 – General classification of fires (ISO/TR 9122-1) Stages of fire Oxygen *%Ratio CO2/CO ** Temperature *°C Irradiance ***kW/m2Stage 1 Non-flaming decomposition

a) Smouldering (self-sustaining) 21 Not applicable <100 Not applicable
b) Non-flaming (oxidative) 5 to 21 Not applicable <500 < 25
c) Non-flaming (pyrolytic) <5 Not applicable <1 000 Not applicable Stage 2

Developing fire (flaming) 10 to 15 100 to 200 400 to 600 20 to 40 Stage 3 Fully developed fire (flaming)

a) Relatively low ventilation 1 to 5 <10 600 to 900 40 to 70
b) Relatively high ventilation 5 to 10 <100 600 to 1 200 50 to 150 *

General environmental condition (average) within compartment. **Mean value in fire plume near to fire. ***Incident irradiance on to test specimen (average). Stage 1 Non-flaming decomposition Stage 2 Developing fire Stage 3 Fully developed fireDecay stage 0 Ignition Flash-over Time

tCompartment temperature IEC

603/05 Figure 1 – Chart of different phases in the development of a fire within a compartment

60695-6-1 ¤ IEC:2005 – 27 – 4.2 Factors affecting smoke production 4.2.1 General Many factors

...

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