ISO/TR 13387-5:1999
(Main)Fire safety engineering — Part 5: Movement of fire effluents
Fire safety engineering — Part 5: Movement of fire effluents
Ingénierie de la sécurité contre l'incendie — Partie 5: Mouvements des effluents du feu
Požarno inženirstvo - 5. del: Širjenje dimnih plinov
General Information
Standards Content (Sample)
SLOVENSKI STANDARD
SIST ISO/TR 13387-5:2001
01-februar-2001
Požarno inženirstvo - 5. del: Širjenje dimnih plinov
Fire safety engineering -- Part 5: Movement of fire effluents
Ingénierie de la sécurité contre l'incendie -- Partie 5: Mouvements des effluents du feu
Ta slovenski standard je istoveten z: ISO/TR 13387-5:1999
ICS:
13.220.01 Varstvo pred požarom na Protection against fire in
splošno general
SIST ISO/TR 13387-5:2001 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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SIST ISO/TR 13387-5:2001
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SIST ISO/TR 13387-5:2001
TECHNICAL ISO/TR
REPORT 13387-5
First edition
1999-10-15
Fire safety engineering —
Part 5:
Movement of fire effluents
Ingénierie de la sécurité contre l'incendie —
Partie 5: Mouvements des effluents du feu
A
Reference number
ISO/TR 13387-5:1999(E)
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SIST ISO/TR 13387-5:2001
ISO/TR 13387-5:1999(E)
Contents
1 Scope .1
2 Normative references .1
3 Terms and definitions .2
4 Symbols and abbreviated terms .2
5 Subsystem 2 of the total design system .3
6 Subsystem 2 evaluations.5
6.1 Movement of fire effluents .5
6.2 Non-thermal fire damage .13
7 Engineering methods .14
7.1 General.14
7.2 Estimation formulae .15
7.3 Zone models.15
7.4 Field models.16
7.5 Experimental methods .18
8 Techniques to control movement of fire effluents .18
Bibliography.20
© ISO 1999
All rights reserved. Unless otherwise specified, 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 Organization for Standardization
Case postale 56 • CH-1211 Genève 20 • Switzerland
Internet iso@iso.ch
Printed in Switzerland
ii
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SIST ISO/TR 13387-5:2001
© ISO
ISO/TR 13387-5:1999(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO
member bodies). The work of preparing International Standards is normally carried out through ISO technical
committees. Each member body interested in a subject for which a technical committee has been established has
the right to be represented on that committee. International organizations, governmental and non-governmental, in
liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical
Commission (IEC) on all matters of electrotechnical standardization.
The main task of ISO technical committees is to prepare International Standards, but in exceptional circumstances a
technical committee may propose the publication of a Technical Report of one of the following types:
type 1, when the required support cannot be obtained for the publication of an International Standard, despite
repeated efforts;
type 2, when the subject is still under technical development or where for any other reason there is the future
but not immediate possibility of an agreement on an International Standard;
type 3, when a technical committee has collected data of a different kind from that which is normally published
as an International Standard (“state of the art“, for example).
Technical Reports of types 1 and 2 are subject to review within three years of publication, to decide whether they
can be transformed into International Standards. Technical Reports of type 3 do not necessarily have to be
reviewed until the data they provide are considered to be no longer valid or useful.
ISO/TR 13387-5, which is a Technical Report of type 2, was prepared by Technical Committee ISO/TC 92, Fire
safety, Subcommittee SC 4, Fire safety engineering.
It is one of eight parts which outlines important aspects which need to be considered in making a fundamental
approach to the provision of fire safety in buildings. The approach ignores any constraints which might apply as a
consequence of regulations or codes; following the approach will not, therefore, necessarily mean compliance with
national regulations.
ISO/TR 13387 consists of the following parts, under the general title Fire safety engineering:
Part 1: Application of fire performance concepts to design objectives
Part 2: Design fire scenarios and design fires
Part 3: Assessment and verification of mathematical fire models
Part 4: Initiation and development of fire and generation of fire effluents
Part 5: Movement of fire effluents
Part 6: Structural response and fire spread beyond the enclosure of origin
Part 7: Detection, activation and suppression
Part 8: Life safety — Occupant behaviour, location and condition
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Introduction
Fire effluent, i.e. smoke and gaseous species, cause a substantial threat to life and property. One of the fire safety
objectives when designing a building is to ensure that the occupants are ultimately able to leave the building without
being subject to hazardous or untenable conditions. In premises with significant financial or cultural value, one of
the fire safety objectives is to prevent the damage to property. To meet these objectives one may either limit the
generation of fire effluent or control the flow of fire effluent. The former is discussed in ISO/TR 13387-4, whereas
the latter is the topic of this Technical Report.
Assessment of fire effluent flow within a building, and assessment and design of smoke control and venting systems
is a common feature in fire safety design of a building. In most of the existing fire safety regulations measures are
taken to control the movement of fire effluents. Typically in prescriptive codes, the requirements are set as the
minimum effective area of smoke vents as a percentage of the total roof area. The required smoke vent area may
vary within the range of 0,25 % to 5 % of the roof area.
Engineering methods for the design of smoke control systems have been available for a long time in the form of
nomograms or calculation methods (see reference [1] of the bibliography). In both approaches, however, the design
of smoke control is treated as an isolated form from the rest of the fire safety design, although in real fires the
movement of fire effluent highly depends on the interaction with other features of the design.
Phenomena controlling smoke movement have been actively studied during recent decades. Calculation methods
and computer codes have been developed to make the necessary evaluations. At the same time advances in
experimental techniques have made it possible to produce input data for the calculation methods and to run
large-scale tests for assessing the validity and limitations of the models.
This part of ISO/TR 13387 is intended for use together with the other Technical Reports produced by SC 4 as
described in clause 5. For some applications this document alone may be sufficient.
Clause 6 of the report describes and provides guidance on the methods available to describe the processes
involved in movement of fire effluent.
Clause 7 describes and provides guidance on the use and evaluation of different types of engineering methods
available to describe the movement of fire effluent, i.e. hand calculations, zone models, field or Computational Fluid
Dynamics (CFD) models, and experiments.
Clause 8 briefly describes different techniques available to control movement of fire effluent. The quantitative
information may be related to specific test conditions and/or specific commercial products, and the application of
data under different conditions may result in significant errors.
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SIST ISO/TR 13387-5:2001
TECHNICAL REPORT © ISO ISO/TR 13387-5:1999(E)
Fire safety engineering —
Part 5:
Movement of fire effluents
1 Scope
This part of ISO/TR 13387 is intended to provide guidance to designers, regulators and fire safety professionals on
the use of engineering methods for the prediction of movement of fire effluents within and outside of a building. It is
not intended as a detailed design guide, but could be used as the basis for the development of such a guide.
This part of ISO/TR 13387 also provides a framework for critically reviewing the suitability of an engineering method
for assessing the potential for movement of fire effluent during the course of fire. The document also provides
guidance on the means to assess the effectiveness of fire safety measures meant to reduce the adverse effects of
movement of fire effluents. The methods for calculating the effects of design fires for use in the design and
assessment of fire safety of a building are also addressed.
2 Normative references
The following normative documents contain provisions which, through reference in this text, constitute provisions of
this part of ISO/TR 13387. For dated references, subsequent amendments to, or revisions of, any of these
publications do not apply. However, parties to agreements based on this part of ISO/TR 13387 are encouraged to
investigate the possibility of applying the most recent editions of the normative documents indicated below. For
undated references, the latest edition of the normative document referred to applies. Members of ISO and IEC
maintain registers of currently valid International Standards.
ISO/TR 13387-1, Fire safety engineering — Part 1: Application of fire performance concepts to design objectives.
ISO/TR 13387-2, Fire safety engineering — Part 2: Design fire scenarios and design fires.
ISO/TR 13387-3, Fire safety engineering — Part 3: Assessment and verification of mathematical fire models.
ISO/TR 13387-4, Fire safety engineering — Part 4: Initiation and development of fire and generation of fire effluents.
ISO/TR 13387-6, Fire safety engineering — Part 6: Structural response and fire spread beyond the enclosure of
origin.
ISO/TR 13387-7, Fire safety engineering — Part 7: Detection, activation and suppression.
ISO/TR 13387-8, Fire safety engineering — Part 8: Life safety — Occupant behaviour, location and condition.
ISO 13943, Fire safety — Vocabulary.
1
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3 Terms and definitions
For the purposes of this part of ISO/TR 13387, the definitions given in ISO 13943, ISO/TR 13387-1 and the
following apply.
3.1
ceiling jet
horizontal gas stream under a ceiling
3.2
extinction coefficient
a constant determining the decay of light intensity in smoke per unit path length, given by K = (1/l) ln(l /l)
0
-1
It is expressed in m .
3.3
fire effluent
all gaseous, particulate or aerosol effluent from combustion or pyrolysis
3.4
opening factor
1/2
A (h ) /A
v v T
1/2
It is expressed in m .
3.5
plume
buoyant gas stream above a localized fire
3.6
vent
an opening for passage of fire effluent out of an enclosure
3.7
ventilation factor
1/2
A (h )
v v
5/2
It is expressed in m .
4 Symbols and abbreviated terms
2
A surface area of fuel, expressed in m
fuel
2
A total area of bounding surfaces in an enclosure, expressed in m
T
2
A area of an opening, expressed in m
v
3
C concentration of species i, expressed in kg/m
i
3
C concentration of species i in a flow into an enclosure, expressed in kg/m
in
c specific heat capacity, expressed in J/(kg·K)
f yield of species X, where X = CO, CO , .
X 2
2
g acceleration due to gravity, expressed in m/s
2
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ISO/TR 13387-5:1999(E)
h height of an opening or height of a shaft, expressed in m
v
2
I intensity of light after passing through smoke, expressed in W/m
2
I intensity of light in clean air, expressed in W/m
0
-1
K extinction coefficient, expressed in m
k thermal conductivity, expressed in W/(m·K)
mass loss rate of fuel, expressed in kg/s&m
fuel
generation rate of species X, where X = CO, CO , ., expressed in kg/s&m
2
X
&
Q heat release rate, expressed in W
P pressure, expressed in Pa
T gas temperature or outside ambient temperature, expressed in K
g
T initial surface temperature or inside temperature, expressed in K
0
t time, expressed in s
3
V volume of enclosure, expressed in m
encl
3
r density, expressed in kg/m
Ddifference (as in DP or Dr)
5 Subsystem 2 of the total design system
The approach adopted in the work of ISO/TC 92/SC 4 is to consider the global objective of fire safety design. The
global design, described in more detail in the framework document ISO/TR 13387-1, is sub-divided into what are
called subsystems of the total design. The key principles of the global design approach are that interdependencies
among the subsystems are evaluated and that pertinent considerations for each subsystem are identified.
In the framework document, the total fire safety design is illustrated by an information bus analogy (see Figure 1).
The information bus has three layers: global information, evaluation and process buses. The information bus
analogy of Subsystem 2 (SS1), movement of fire effluents, is illustrated in Figure 1. SS2 draws on other
subsystems for a prescription or characterization of fire. SS2 provides information on movement of fire effluents for
the other subsystems to be employed.
SS1, for example, provides information on heat, smoke and species generation, which then is applied by SS2 for
the calculation of smoke movement out of the room and in the building. The information may then be used by SS5
to assess evacuation and rescue provisions. The prediction of activation of fire detectors, sprinklers or smoke vent
opening devices is provided by SS4. The prediction of spread through barriers or openings beyond the room of fire
origin is provided by SS3.
The evaluations and the processes needed to do the evaluations are discussed in detail in clause 6.
3
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ISO/TR 13387-5:1999(E)
ISO TC 92/SC 4 FIRE SAFETY ENGINEERING BUS SYSTEM
Subsystem 2 (SS2) — Movement of fire effluents
For explanations of terms used in conjunction with the global information bus, see ISO/TR 13387-1.
Figure 1 — Illustration of the global information, evaluation and process buses for SS2
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6 Subsystem 2 evaluations
In this clause various processes of movement of fire effluents and the threat to life, property and environment shall
be discussed. The required input information and the possible output information shall be identified. Areas for which
shortages in engineering methods and lack of knowledge are known to exist will be addressed. The text will make
reference to existing acknowledged literature, whenever such is available.
6.1 Movement of fire effluents
6.1.1 Role in fire safety engineering design
The flow chart in Figure 2 outlines the main stages of evaluating the movement of fire effluents within and beyond
the room of origin. In using the flow chart it is assumed that all the source terms needed for evaluating movement of
fire effluents shall be given by SS1 (ISO/TR 13387-4) or as design fires described in ISO/TR 13387-2.
6.1.1.1 Input
The evaluation of movement of fire effluents (see Figure 1) may require as input information the following:
building parameters (for example, thermal properties, geometry, location of openings, etc.);
environmental parameters (for example, velocities and prevailing direction of wind, outside temperature,
temperature distribution in the building, internal air movements caused by mechanical ventilation systems);
size of fire/smoke (for example, rate of heat release of the fire, plume mass flow, smoke generation rate);
thermal profile (for example, temperature distribution in the plume);
pressure/velocity profile (for example, pressure profile in the room of origin);
effluent species profile (for example, species generation rate, mass flow of species in the plume).
6.1.1.2 Output
The evaluation of movement of fire effluents (see Figure 1) provides information about the following:
size of fire and/or smoke (for example, smoke density distribution in the building);
thermal profile (temperature and heat flux distribution in the building);
pressure/velocity profile (for example, pressure at smoke vents, flow through vents, velocity in the corridor jet);
effluent species profile (for example, gaseous species concentration distribution in the building);
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The dark arrows indicate interaction with the global information in Figure 1.
QDR = Qualitative design review has been discussed in ISO/TR 13387-1.
Figure 2 — Flow chart for movement of fire effluents
6
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6.1.2 Processes of movement of fire effluents
6.1.2.1 General
The spread of a fire effluent is caused, primarily, by its buoyancy and the increase in volume resulting from the
entrainment of air. Its spread can be controlled by means of smoke barriers, smoke extraction and opposing flows
(pressure differentials). The techniques most commonly used to limit the extent of smoke spread are summarized in
clause 8.
The temperature of a fire effluent, and hence its buoyancy, depends on the rate of heat release of the fire and the
entrainment of cool air into the smoke plume. Entrainment reduces both the concentration of smoke particles and
the temperature. This increases visibility but also increases the volume of smoke.
The effluent plume from a fire within an enclosure will rise to ceiling level and then spread horizontally to form a
layer beneath the ceiling. Generally, the mass flow of the burnt fuel is so small compared with the mass flow of the
entrained air that for practical purposes it may be ignored. For smooth ceilings or ceilings of limited extent the
entrainment is small during horizontal flow and can usually be ignored. However, when the smoke flows around
obstacles (for example, beams) or through apertures (for example, a doorway), the rate of entrainment increases.
Smouldering fires typically have low buoyancy and the smoke may never form an upper layer due to higher initial
temperature close to the ceiling or forced flow in the enclosure.
6.1.2.2 Plumes
The buoyant gas stream above a localized burning area is called a fire plume. The fire plume is characterized by its
temperature and velocity distribution, which can be transformed into mass and energy flows at various heights
above the source.
Plume models have been a subject of active research especially in the early 1980's. By simplifying approximations
to basic laws and fits to experimental data, a number of semi-empirical plume models have been developed.
General discussions on fire plumes have been presented, for example, in detail in reference [2] and in a
[5]
summarized form in references [3] and [4]. Useful reading to the user of plume models is also the review paper in
which various expressions describing plume and ceiling flows are compared and discussed. Several papers
comparing the results obtained by plume models have been published in journals or presented in conferences
during the last ten years; one of the most recent and useful ones is reference [6].
Many of the plume models used in fire-safety engineering describe the fire as a point source. The effect of the finite
diameter of the fire is taken into account by assuming the fire is a virtual source below or above the actual fuel
surface depending on the diameter and the rate of heat release of the fire, i.e., the ratio of the buoyancy and the
momentum of the gas stream. Expressions can be found, however, also for sources of other geometries. At one
extreme a fire source can be regarded as a two-dimensional line source. Non-circular flat fuel sources, which are
almost square, can be treated as circular sources with an effective diameter resulting in the same area as in the real
source. For some burning objects like rack storage the depth of the fire source cannot be neglected. Semi-empirical
equations are derived for these special cases.
If the burning object is close to a wall or a corner, the plume equations for circular fire sources are transferred by
using a virtual source extending as a mirror image on the other side of the wall. The simple imaging method results
in temperatures which are close to those measured in wall or corner plumes, although the effects of the wall
surfaces on the turbulence are neglected. For finite sources adjacent to the wall, the plume expressions are scarce,
and considerable engineering judgement is needed when analysing such fire scenarios, for example, by zone
models (see 7.3).
When selecting a fire plume one should pay attention to the assumptions made when developing the plume
expression. Usually, the heat release rate in the plume property expressions equals the convective fraction of heat
release rate. The convective heat release rate is typically assumed to be 70 % of the total heat release rate.
[7]
However, the commonly used McCaffrey plume expressions use the total heat release rate . The expressions are
always fitted to a limited set of experimental data and therefore the empirical coefficients may not be applicable to
the scenario under consideration. The most commonly used plume models have been originally calibrated against
small fire (heat release rates , 1 MW). It is necessary to be particularly careful when extending the application to a
7
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larger scale, because extrapolation may lead to systematic errors. There are, however, a large number of examples
in which the plume models implemented in zone models have been able to produce results which compare
favourably with experimental data.
The plume expressions have usually been derived from steady-state fires under quiescent ambient conditions. In
real buildings significant cross winds can be present either due to air flows existing before the fire or generated by
the fire itself. These usually cause better entrainment and therefore lower temperatures but bigger mass flows in the
plume. Whether this is can be considered safe or unsafe will depend on the purpose of the calculation.
In engineering applications, if no information of the exact fire location exists, it should be assumed that the fire
source is directly below the object of interest.
Expressions are also available for plumes emerging from windows with or without balconies.
6.1.2.2.1 Input
The input information in plume flow expressions are:
rate of heat release (total and convective fraction);
diameter of the base of the fire;
ambient temperature.
6.1.2.2.2 Output
The outputs of plume expressions are:
average temperature and velocity at various positions in the plume;
mass flow in the plume at various heights.
6.1.2.3 Ceiling jets
When the plume hits the ceiling, a ceiling jet is formed carrying the combustion products away from the line of fire
axis. The ceiling jet is characterized by the same quantities as the vertical plume. However, considerably less work
has been done to develop semi-empirical expressions for ceiling jet flows than for plume flows.
[8],[9]
The most commonly used ceiling jet expressions were published in the early 1970's . Reference [9] also
2
contains expressions for maximum temperatures and velocities in t -fires under an unconfined ceiling and in steady
fires under confined ceilings.
Transient flow of a ceiling jet is especially important in corridors, because it may produce the first cue of the fire at a
remote location and determine when hazardous conditions begin to be formed. Reference [9] includes also a brief
discussion on the phenomena and appropriate references to scientific literature.
Friction between the ceiling jet and the ceiling slows the velocity near the ceiling surface. The reduced velocity may
be significant for the response of ceiling mounted detectors or sprinklers. Detailed analytical expressions exist for
the flow profile in the ceiling jet, but as a crude estimate the maximum occurs at a distance of 2 % of the distance
from the fire source to the ceiling.
6.1.2.3.1 Input
The input information in plume flow expressions are:
heat release rate (total and convective fraction);
diameter of the base of the fire;
ambient temperature.
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6.1.2.3.2 Output
The outputs of plume expressions are:
averaged temperature and velocity at various positions in the ceiling jet;
mass and energy flux in the ceiling jet at various radial distances.
6.1.2.4 Hot upper layer formation
Due to buoyancy the hot combustion products collect in the upper part of the room. For ease of calculation it is
commonly assumed that the upper layer is sufficiently homogeneous so that it can be characterized by a single
temperature. The depth and the temperature of the layer depend on the mass and energy flow into the layer, the
heat losses to the bounding walls and the lower part of the room as well as the mass and convective energy flow
out of the room. The formation of a homogeneous upper layer is usually assumed by zone models.
The assumption of a homogeneous upper layer may not be valid if the fire grows rapidly, i.e. if the temperature of
the plume as it enters the layer is always considerably higher than the average temperature of the layer. The hot
plume penetrates the layer and the warmer combustion products modified by turbulent mixing always form a new
layer close to the ceiling. Therefore, there may be a continuous temperature gradient in the layer. The
homogeneous layer concept may not hold true if the floor area of the enclosure is small compared to the area of the
fire source or the width of the plume before it hits the upper layer. At the other extreme, if the floor area of the
enclosure is large, the temperature in the ceiling jet may decrease considerably close to the walls resulting in
significant temperature differences at different radial positions. Unfortunately, no quantitative limits have been
established to determine when the homogeneous layer assumption is to be applicable.
A useful discussion on the processes relevant to hot upper layer formation can be found, for example, in references
[10] and [11].
When evaluating the formation of the upper gas layer, it is important to consider any enclosure characteristics that
may have an effect on the plume. In high-ceiling and large-volume enclosures with temperature stratification, the
entrainment of cool air into the plume may cause the plume temperature to become so low (relative to the enclosure
temperature) that the relative buoyancy will be insufficient for the plume to reach the ceiling. In such cases, the
upper layer will stratify at some level below the ceiling until additional thermal energy is added to the plume. Should
stratification occur, it is unlikely that fire signatures will reach ceiling-mounted fire detection devices, and initiation of
[11]
active fire protection measures may be significantly delayed .
The likelihood of stratification can be evaluated by comparing the maximum plume temperatures and the maximum
[12], [13]
ambient ceiling-level temperatures at the location of interest . The maximum ambient ceiling-level
temperature is high
...
TECHNICAL ISO/TR
REPORT 13387-5
First edition
1999-10-15
Fire safety engineering —
Part 5:
Movement of fire effluents
Ingénierie de la sécurité contre l'incendie —
Partie 5: Mouvements des effluents du feu
A
Reference number
ISO/TR 13387-5:1999(E)
---------------------- Page: 1 ----------------------
ISO/TR 13387-5:1999(E)
Contents
1 Scope .1
2 Normative references .1
3 Terms and definitions .2
4 Symbols and abbreviated terms .2
5 Subsystem 2 of the total design system .3
6 Subsystem 2 evaluations.5
6.1 Movement of fire effluents .5
6.2 Non-thermal fire damage .13
7 Engineering methods .14
7.1 General.14
7.2 Estimation formulae .15
7.3 Zone models.15
7.4 Field models.16
7.5 Experimental methods .18
8 Techniques to control movement of fire effluents .18
Bibliography.20
© ISO 1999
All rights reserved. Unless otherwise specified, 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 Organization for Standardization
Case postale 56 • CH-1211 Genève 20 • Switzerland
Internet iso@iso.ch
Printed in Switzerland
ii
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© ISO
ISO/TR 13387-5:1999(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO
member bodies). The work of preparing International Standards is normally carried out through ISO technical
committees. Each member body interested in a subject for which a technical committee has been established has
the right to be represented on that committee. International organizations, governmental and non-governmental, in
liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical
Commission (IEC) on all matters of electrotechnical standardization.
The main task of ISO technical committees is to prepare International Standards, but in exceptional circumstances a
technical committee may propose the publication of a Technical Report of one of the following types:
type 1, when the required support cannot be obtained for the publication of an International Standard, despite
repeated efforts;
type 2, when the subject is still under technical development or where for any other reason there is the future
but not immediate possibility of an agreement on an International Standard;
type 3, when a technical committee has collected data of a different kind from that which is normally published
as an International Standard (“state of the art“, for example).
Technical Reports of types 1 and 2 are subject to review within three years of publication, to decide whether they
can be transformed into International Standards. Technical Reports of type 3 do not necessarily have to be
reviewed until the data they provide are considered to be no longer valid or useful.
ISO/TR 13387-5, which is a Technical Report of type 2, was prepared by Technical Committee ISO/TC 92, Fire
safety, Subcommittee SC 4, Fire safety engineering.
It is one of eight parts which outlines important aspects which need to be considered in making a fundamental
approach to the provision of fire safety in buildings. The approach ignores any constraints which might apply as a
consequence of regulations or codes; following the approach will not, therefore, necessarily mean compliance with
national regulations.
ISO/TR 13387 consists of the following parts, under the general title Fire safety engineering:
Part 1: Application of fire performance concepts to design objectives
Part 2: Design fire scenarios and design fires
Part 3: Assessment and verification of mathematical fire models
Part 4: Initiation and development of fire and generation of fire effluents
Part 5: Movement of fire effluents
Part 6: Structural response and fire spread beyond the enclosure of origin
Part 7: Detection, activation and suppression
Part 8: Life safety — Occupant behaviour, location and condition
iii
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© ISO
ISO/TR 13387-5:1999(E)
Introduction
Fire effluent, i.e. smoke and gaseous species, cause a substantial threat to life and property. One of the fire safety
objectives when designing a building is to ensure that the occupants are ultimately able to leave the building without
being subject to hazardous or untenable conditions. In premises with significant financial or cultural value, one of
the fire safety objectives is to prevent the damage to property. To meet these objectives one may either limit the
generation of fire effluent or control the flow of fire effluent. The former is discussed in ISO/TR 13387-4, whereas
the latter is the topic of this Technical Report.
Assessment of fire effluent flow within a building, and assessment and design of smoke control and venting systems
is a common feature in fire safety design of a building. In most of the existing fire safety regulations measures are
taken to control the movement of fire effluents. Typically in prescriptive codes, the requirements are set as the
minimum effective area of smoke vents as a percentage of the total roof area. The required smoke vent area may
vary within the range of 0,25 % to 5 % of the roof area.
Engineering methods for the design of smoke control systems have been available for a long time in the form of
nomograms or calculation methods (see reference [1] of the bibliography). In both approaches, however, the design
of smoke control is treated as an isolated form from the rest of the fire safety design, although in real fires the
movement of fire effluent highly depends on the interaction with other features of the design.
Phenomena controlling smoke movement have been actively studied during recent decades. Calculation methods
and computer codes have been developed to make the necessary evaluations. At the same time advances in
experimental techniques have made it possible to produce input data for the calculation methods and to run
large-scale tests for assessing the validity and limitations of the models.
This part of ISO/TR 13387 is intended for use together with the other Technical Reports produced by SC 4 as
described in clause 5. For some applications this document alone may be sufficient.
Clause 6 of the report describes and provides guidance on the methods available to describe the processes
involved in movement of fire effluent.
Clause 7 describes and provides guidance on the use and evaluation of different types of engineering methods
available to describe the movement of fire effluent, i.e. hand calculations, zone models, field or Computational Fluid
Dynamics (CFD) models, and experiments.
Clause 8 briefly describes different techniques available to control movement of fire effluent. The quantitative
information may be related to specific test conditions and/or specific commercial products, and the application of
data under different conditions may result in significant errors.
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TECHNICAL REPORT © ISO ISO/TR 13387-5:1999(E)
Fire safety engineering —
Part 5:
Movement of fire effluents
1 Scope
This part of ISO/TR 13387 is intended to provide guidance to designers, regulators and fire safety professionals on
the use of engineering methods for the prediction of movement of fire effluents within and outside of a building. It is
not intended as a detailed design guide, but could be used as the basis for the development of such a guide.
This part of ISO/TR 13387 also provides a framework for critically reviewing the suitability of an engineering method
for assessing the potential for movement of fire effluent during the course of fire. The document also provides
guidance on the means to assess the effectiveness of fire safety measures meant to reduce the adverse effects of
movement of fire effluents. The methods for calculating the effects of design fires for use in the design and
assessment of fire safety of a building are also addressed.
2 Normative references
The following normative documents contain provisions which, through reference in this text, constitute provisions of
this part of ISO/TR 13387. For dated references, subsequent amendments to, or revisions of, any of these
publications do not apply. However, parties to agreements based on this part of ISO/TR 13387 are encouraged to
investigate the possibility of applying the most recent editions of the normative documents indicated below. For
undated references, the latest edition of the normative document referred to applies. Members of ISO and IEC
maintain registers of currently valid International Standards.
ISO/TR 13387-1, Fire safety engineering — Part 1: Application of fire performance concepts to design objectives.
ISO/TR 13387-2, Fire safety engineering — Part 2: Design fire scenarios and design fires.
ISO/TR 13387-3, Fire safety engineering — Part 3: Assessment and verification of mathematical fire models.
ISO/TR 13387-4, Fire safety engineering — Part 4: Initiation and development of fire and generation of fire effluents.
ISO/TR 13387-6, Fire safety engineering — Part 6: Structural response and fire spread beyond the enclosure of
origin.
ISO/TR 13387-7, Fire safety engineering — Part 7: Detection, activation and suppression.
ISO/TR 13387-8, Fire safety engineering — Part 8: Life safety — Occupant behaviour, location and condition.
ISO 13943, Fire safety — Vocabulary.
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3 Terms and definitions
For the purposes of this part of ISO/TR 13387, the definitions given in ISO 13943, ISO/TR 13387-1 and the
following apply.
3.1
ceiling jet
horizontal gas stream under a ceiling
3.2
extinction coefficient
a constant determining the decay of light intensity in smoke per unit path length, given by K = (1/l) ln(l /l)
0
-1
It is expressed in m .
3.3
fire effluent
all gaseous, particulate or aerosol effluent from combustion or pyrolysis
3.4
opening factor
1/2
A (h ) /A
v v T
1/2
It is expressed in m .
3.5
plume
buoyant gas stream above a localized fire
3.6
vent
an opening for passage of fire effluent out of an enclosure
3.7
ventilation factor
1/2
A (h )
v v
5/2
It is expressed in m .
4 Symbols and abbreviated terms
2
A surface area of fuel, expressed in m
fuel
2
A total area of bounding surfaces in an enclosure, expressed in m
T
2
A area of an opening, expressed in m
v
3
C concentration of species i, expressed in kg/m
i
3
C concentration of species i in a flow into an enclosure, expressed in kg/m
in
c specific heat capacity, expressed in J/(kg·K)
f yield of species X, where X = CO, CO , .
X 2
2
g acceleration due to gravity, expressed in m/s
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h height of an opening or height of a shaft, expressed in m
v
2
I intensity of light after passing through smoke, expressed in W/m
2
I intensity of light in clean air, expressed in W/m
0
-1
K extinction coefficient, expressed in m
k thermal conductivity, expressed in W/(m·K)
mass loss rate of fuel, expressed in kg/s&m
fuel
generation rate of species X, where X = CO, CO , ., expressed in kg/s&m
2
X
&
Q heat release rate, expressed in W
P pressure, expressed in Pa
T gas temperature or outside ambient temperature, expressed in K
g
T initial surface temperature or inside temperature, expressed in K
0
t time, expressed in s
3
V volume of enclosure, expressed in m
encl
3
r density, expressed in kg/m
Ddifference (as in DP or Dr)
5 Subsystem 2 of the total design system
The approach adopted in the work of ISO/TC 92/SC 4 is to consider the global objective of fire safety design. The
global design, described in more detail in the framework document ISO/TR 13387-1, is sub-divided into what are
called subsystems of the total design. The key principles of the global design approach are that interdependencies
among the subsystems are evaluated and that pertinent considerations for each subsystem are identified.
In the framework document, the total fire safety design is illustrated by an information bus analogy (see Figure 1).
The information bus has three layers: global information, evaluation and process buses. The information bus
analogy of Subsystem 2 (SS1), movement of fire effluents, is illustrated in Figure 1. SS2 draws on other
subsystems for a prescription or characterization of fire. SS2 provides information on movement of fire effluents for
the other subsystems to be employed.
SS1, for example, provides information on heat, smoke and species generation, which then is applied by SS2 for
the calculation of smoke movement out of the room and in the building. The information may then be used by SS5
to assess evacuation and rescue provisions. The prediction of activation of fire detectors, sprinklers or smoke vent
opening devices is provided by SS4. The prediction of spread through barriers or openings beyond the room of fire
origin is provided by SS3.
The evaluations and the processes needed to do the evaluations are discussed in detail in clause 6.
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ISO TC 92/SC 4 FIRE SAFETY ENGINEERING BUS SYSTEM
Subsystem 2 (SS2) — Movement of fire effluents
For explanations of terms used in conjunction with the global information bus, see ISO/TR 13387-1.
Figure 1 — Illustration of the global information, evaluation and process buses for SS2
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6 Subsystem 2 evaluations
In this clause various processes of movement of fire effluents and the threat to life, property and environment shall
be discussed. The required input information and the possible output information shall be identified. Areas for which
shortages in engineering methods and lack of knowledge are known to exist will be addressed. The text will make
reference to existing acknowledged literature, whenever such is available.
6.1 Movement of fire effluents
6.1.1 Role in fire safety engineering design
The flow chart in Figure 2 outlines the main stages of evaluating the movement of fire effluents within and beyond
the room of origin. In using the flow chart it is assumed that all the source terms needed for evaluating movement of
fire effluents shall be given by SS1 (ISO/TR 13387-4) or as design fires described in ISO/TR 13387-2.
6.1.1.1 Input
The evaluation of movement of fire effluents (see Figure 1) may require as input information the following:
building parameters (for example, thermal properties, geometry, location of openings, etc.);
environmental parameters (for example, velocities and prevailing direction of wind, outside temperature,
temperature distribution in the building, internal air movements caused by mechanical ventilation systems);
size of fire/smoke (for example, rate of heat release of the fire, plume mass flow, smoke generation rate);
thermal profile (for example, temperature distribution in the plume);
pressure/velocity profile (for example, pressure profile in the room of origin);
effluent species profile (for example, species generation rate, mass flow of species in the plume).
6.1.1.2 Output
The evaluation of movement of fire effluents (see Figure 1) provides information about the following:
size of fire and/or smoke (for example, smoke density distribution in the building);
thermal profile (temperature and heat flux distribution in the building);
pressure/velocity profile (for example, pressure at smoke vents, flow through vents, velocity in the corridor jet);
effluent species profile (for example, gaseous species concentration distribution in the building);
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The dark arrows indicate interaction with the global information in Figure 1.
QDR = Qualitative design review has been discussed in ISO/TR 13387-1.
Figure 2 — Flow chart for movement of fire effluents
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6.1.2 Processes of movement of fire effluents
6.1.2.1 General
The spread of a fire effluent is caused, primarily, by its buoyancy and the increase in volume resulting from the
entrainment of air. Its spread can be controlled by means of smoke barriers, smoke extraction and opposing flows
(pressure differentials). The techniques most commonly used to limit the extent of smoke spread are summarized in
clause 8.
The temperature of a fire effluent, and hence its buoyancy, depends on the rate of heat release of the fire and the
entrainment of cool air into the smoke plume. Entrainment reduces both the concentration of smoke particles and
the temperature. This increases visibility but also increases the volume of smoke.
The effluent plume from a fire within an enclosure will rise to ceiling level and then spread horizontally to form a
layer beneath the ceiling. Generally, the mass flow of the burnt fuel is so small compared with the mass flow of the
entrained air that for practical purposes it may be ignored. For smooth ceilings or ceilings of limited extent the
entrainment is small during horizontal flow and can usually be ignored. However, when the smoke flows around
obstacles (for example, beams) or through apertures (for example, a doorway), the rate of entrainment increases.
Smouldering fires typically have low buoyancy and the smoke may never form an upper layer due to higher initial
temperature close to the ceiling or forced flow in the enclosure.
6.1.2.2 Plumes
The buoyant gas stream above a localized burning area is called a fire plume. The fire plume is characterized by its
temperature and velocity distribution, which can be transformed into mass and energy flows at various heights
above the source.
Plume models have been a subject of active research especially in the early 1980's. By simplifying approximations
to basic laws and fits to experimental data, a number of semi-empirical plume models have been developed.
General discussions on fire plumes have been presented, for example, in detail in reference [2] and in a
[5]
summarized form in references [3] and [4]. Useful reading to the user of plume models is also the review paper in
which various expressions describing plume and ceiling flows are compared and discussed. Several papers
comparing the results obtained by plume models have been published in journals or presented in conferences
during the last ten years; one of the most recent and useful ones is reference [6].
Many of the plume models used in fire-safety engineering describe the fire as a point source. The effect of the finite
diameter of the fire is taken into account by assuming the fire is a virtual source below or above the actual fuel
surface depending on the diameter and the rate of heat release of the fire, i.e., the ratio of the buoyancy and the
momentum of the gas stream. Expressions can be found, however, also for sources of other geometries. At one
extreme a fire source can be regarded as a two-dimensional line source. Non-circular flat fuel sources, which are
almost square, can be treated as circular sources with an effective diameter resulting in the same area as in the real
source. For some burning objects like rack storage the depth of the fire source cannot be neglected. Semi-empirical
equations are derived for these special cases.
If the burning object is close to a wall or a corner, the plume equations for circular fire sources are transferred by
using a virtual source extending as a mirror image on the other side of the wall. The simple imaging method results
in temperatures which are close to those measured in wall or corner plumes, although the effects of the wall
surfaces on the turbulence are neglected. For finite sources adjacent to the wall, the plume expressions are scarce,
and considerable engineering judgement is needed when analysing such fire scenarios, for example, by zone
models (see 7.3).
When selecting a fire plume one should pay attention to the assumptions made when developing the plume
expression. Usually, the heat release rate in the plume property expressions equals the convective fraction of heat
release rate. The convective heat release rate is typically assumed to be 70 % of the total heat release rate.
[7]
However, the commonly used McCaffrey plume expressions use the total heat release rate . The expressions are
always fitted to a limited set of experimental data and therefore the empirical coefficients may not be applicable to
the scenario under consideration. The most commonly used plume models have been originally calibrated against
small fire (heat release rates , 1 MW). It is necessary to be particularly careful when extending the application to a
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larger scale, because extrapolation may lead to systematic errors. There are, however, a large number of examples
in which the plume models implemented in zone models have been able to produce results which compare
favourably with experimental data.
The plume expressions have usually been derived from steady-state fires under quiescent ambient conditions. In
real buildings significant cross winds can be present either due to air flows existing before the fire or generated by
the fire itself. These usually cause better entrainment and therefore lower temperatures but bigger mass flows in the
plume. Whether this is can be considered safe or unsafe will depend on the purpose of the calculation.
In engineering applications, if no information of the exact fire location exists, it should be assumed that the fire
source is directly below the object of interest.
Expressions are also available for plumes emerging from windows with or without balconies.
6.1.2.2.1 Input
The input information in plume flow expressions are:
rate of heat release (total and convective fraction);
diameter of the base of the fire;
ambient temperature.
6.1.2.2.2 Output
The outputs of plume expressions are:
average temperature and velocity at various positions in the plume;
mass flow in the plume at various heights.
6.1.2.3 Ceiling jets
When the plume hits the ceiling, a ceiling jet is formed carrying the combustion products away from the line of fire
axis. The ceiling jet is characterized by the same quantities as the vertical plume. However, considerably less work
has been done to develop semi-empirical expressions for ceiling jet flows than for plume flows.
[8],[9]
The most commonly used ceiling jet expressions were published in the early 1970's . Reference [9] also
2
contains expressions for maximum temperatures and velocities in t -fires under an unconfined ceiling and in steady
fires under confined ceilings.
Transient flow of a ceiling jet is especially important in corridors, because it may produce the first cue of the fire at a
remote location and determine when hazardous conditions begin to be formed. Reference [9] includes also a brief
discussion on the phenomena and appropriate references to scientific literature.
Friction between the ceiling jet and the ceiling slows the velocity near the ceiling surface. The reduced velocity may
be significant for the response of ceiling mounted detectors or sprinklers. Detailed analytical expressions exist for
the flow profile in the ceiling jet, but as a crude estimate the maximum occurs at a distance of 2 % of the distance
from the fire source to the ceiling.
6.1.2.3.1 Input
The input information in plume flow expressions are:
heat release rate (total and convective fraction);
diameter of the base of the fire;
ambient temperature.
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6.1.2.3.2 Output
The outputs of plume expressions are:
averaged temperature and velocity at various positions in the ceiling jet;
mass and energy flux in the ceiling jet at various radial distances.
6.1.2.4 Hot upper layer formation
Due to buoyancy the hot combustion products collect in the upper part of the room. For ease of calculation it is
commonly assumed that the upper layer is sufficiently homogeneous so that it can be characterized by a single
temperature. The depth and the temperature of the layer depend on the mass and energy flow into the layer, the
heat losses to the bounding walls and the lower part of the room as well as the mass and convective energy flow
out of the room. The formation of a homogeneous upper layer is usually assumed by zone models.
The assumption of a homogeneous upper layer may not be valid if the fire grows rapidly, i.e. if the temperature of
the plume as it enters the layer is always considerably higher than the average temperature of the layer. The hot
plume penetrates the layer and the warmer combustion products modified by turbulent mixing always form a new
layer close to the ceiling. Therefore, there may be a continuous temperature gradient in the layer. The
homogeneous layer concept may not hold true if the floor area of the enclosure is small compared to the area of the
fire source or the width of the plume before it hits the upper layer. At the other extreme, if the floor area of the
enclosure is large, the temperature in the ceiling jet may decrease considerably close to the walls resulting in
significant temperature differences at different radial positions. Unfortunately, no quantitative limits have been
established to determine when the homogeneous layer assumption is to be applicable.
A useful discussion on the processes relevant to hot upper layer formation can be found, for example, in references
[10] and [11].
When evaluating the formation of the upper gas layer, it is important to consider any enclosure characteristics that
may have an effect on the plume. In high-ceiling and large-volume enclosures with temperature stratification, the
entrainment of cool air into the plume may cause the plume temperature to become so low (relative to the enclosure
temperature) that the relative buoyancy will be insufficient for the plume to reach the ceiling. In such cases, the
upper layer will stratify at some level below the ceiling until additional thermal energy is added to the plume. Should
stratification occur, it is unlikely that fire signatures will reach ceiling-mounted fire detection devices, and initiation of
[11]
active fire protection measures may be significantly delayed .
The likelihood of stratification can be evaluated by comparing the maximum plume temperatures and the maximum
[12], [13]
ambient ceiling-level temperatures at the location of interest . The maximum ambient ceiling-level
temperature is highly dependent on the height and volume of the enclosure, on the building construction, on the
interior finish materials, and the building location (i.e., exterior environmental conditions). It has been reported, for
example, that the difference in ambient temperature from floor to ceiling can be of the order of 50 °C in some atria
[11]
with glazed ceilings . A useful discussion relevant to stratification and fire detection can be found in
reference [11].
If the plume temperature is high enough, the plume may hit the ceiling and a radial ceiling jet is formed. The
temperature of this primary flow may be considerably higher than the average upper zone temperature. For thermal
detectors and sprinklers this means a faster response but for structures the higher local temperatures may cause
critical conditions (ignition, collapse) to occur much faster than if estimated based on average upper layer
temperatures.
In structural design, the possibility of localized higher temperatures should always be considered. If no location
spec
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