Fire resistance tests -- Guidelines for the design and conduct of non-furnace-based large-scale tests and simulation

ISO/TR 15658:2009 specifies procedures for the design, performance and reporting of fire tests which are not performed using standardized test equipment, such as furnaces or test chambers, and which are primarily duration- or time-based. It is applicable to all ‘natural' fire tests, which set out to evaluate the behaviour of structural frames, rooms (or a suite of rooms forming part of a building), with respect to fully developed fire conditions, regardless of whether or not the heat input is by means of natural sources, e.g. cribs or burners. It is not applicable to ‘reaction-to-fire' large-scale tests, which are primarily designed to evaluate materials and for which the heating rate is slower and the maximum rate of heat release is lower than that which would occur at full development.

Essais de résistance au feu -- Lignes directrices pour la conception et la conduite d'essais et de simulations à large échelle non basés sur les fours

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Publication Date
27-Jul-2009
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6060 - International Standard published
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13-Jul-2009
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TECHNICAL ISO/TR
REPORT 15658
First edition
2009-08-01
Fire resistance tests — Guidelines for the
design and conduct of non-furnace-based
large-scale tests and simulation
Essais de résistance au feu — Lignes directrices pour la conception et
la conduite d'essais et de simulations à large échelle non basés sur les
fours
Reference number
ISO/TR 15658:2009(E)
ISO 2009
---------------------- Page: 1 ----------------------
ISO/TR 15658:2009(E)
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ii © ISO 2009 – All rights reserved
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ISO/TR 15658:2009(E)
Contents Page

Foreword............................................................................................................................................................ iv

Introduction ........................................................................................................................................................ v

1 Scope ..................................................................................................................................................... 1

2 Normative references ........................................................................................................................... 1

3 Terms and definitions........................................................................................................................... 1

4 Test design requirements .................................................................................................................... 2

4.1 General................................................................................................................................................... 2

4.2 Ambient environmental conditions..................................................................................................... 2

4.3 Size of the test assembly ..................................................................................................................... 3

4.4 Construction of the test assembly...................................................................................................... 4

4.5 Test specimen ....................................................................................................................................... 5

4.6 Selection of heating conditions .......................................................................................................... 6

4.7 Selection of ventilation conditions ..................................................................................................... 7

4.8 Selection of exhaust conditions.......................................................................................................... 7

4.9 Selection of decay conditions (if controlled)..................................................................................... 8

5 Test conditions ..................................................................................................................................... 8

5.1 Ambient conditions .............................................................................................................................. 8

5.2 Test conditions — Thermal.................................................................................................................. 9

5.3 Test conditions — Pressure ................................................................................................................ 9

5.4 Test conditions — Mechanical .......................................................................................................... 10

5.5 Timing of the test................................................................................................................................ 10

5.6 Output measurements........................................................................................................................ 10

5.7 Data recording and storage ............................................................................................................... 11

6 Test procedure .................................................................................................................................... 11

6.1 Ignition ................................................................................................................................................. 11

6.2 Safety procedures............................................................................................................................... 11

6.3 Monitoring ........................................................................................................................................... 11

6.4 Observations ....................................................................................................................................... 12

6.5 Termination and extinguishing ......................................................................................................... 12

6.6 Post-test analysis ............................................................................................................................... 12

7 Test report ........................................................................................................................................... 12

7.1 Stating the objective........................................................................................................................... 12

7.2 Characterization of the experimental conditions ............................................................................ 12

7.3 Expression of the results................................................................................................................... 12

7.4 Description of the test specimen ...................................................................................................... 13

7.5 Reporting — Electronic media .......................................................................................................... 13

7.6 Expression of the validity or field of application of the result....................................................... 13

Bibliography ..................................................................................................................................................... 14

© ISO 2009 – All rights reserved iii
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ISO/TR 15658:2009(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.

International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.

The main task of technical committees is to prepare International Standards. Draft International Standards

adopted by the technical committees are circulated to the member bodies for voting. Publication as an

International Standard requires approval by at least 75 % of the member bodies casting a vote.

In exceptional circumstances, 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), it may decide by a

simple majority vote of its participating members to publish a Technical Report. A Technical Report is entirely

informative in nature and does not have to be reviewed until the data it provides are considered to be no

longer valid or useful.

Attention is drawn to the possibility that some of the elements of this document may be the subject of patent

rights. ISO shall not be held responsible for identifying any or all such patent rights.

ISO/TR 15658 was prepared by Technical Committee ISO/TC 92, Fire Safety, Subcommittee SC 2, Fire

Containment.
iv © ISO 2009 – All rights reserved
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ISO/TR 15658:2009(E)
Introduction

The fire engineering community have often had to resort to non-furnace-based tests in order to establish

certain characteristics of the fire behaviour of products, or constructions that cannot be obtained using

standard methods. The reasons for these are many, including:
a) size of the test element;
b) interaction between components or elements;
c) fire loads and heating rates;
d) achievement of realistic levels of restraint;
e) realistic oxygen availability.

Fire modelling is also being increasingly used to resolve the complex problems that many modern buildings

produce. Currently, modelling is often limited by a lack of data and large-scale “natural” tests are increasingly

being used to establish the missing information, and, by using the protocol described in this Technical Report,

the quality, comparability and validity of the information/data should be significantly improved.

Unfortunately, the design of such tests is often controlled by the availability of space, equipment, cost,

environment, etc. and these sometimes compromise the scientific value of the experiment and make the

results hard to compare with other experiments performed in other laboratories or countries. This lack of

comparability has in the past prevented the value of the findings from being maximized.

When an experiment has been set-up without adequate consideration of the objectives and the test

parameters, it is difficult to apply a scientifically valid field of application to the result. As a consequence, the

data of findings are frequently wrongly applied to constructions subsequent to the test.

The objective of this Technical Report is to harmonize the approach to the design, performance and reporting

of such experiments, in order to increase the possibility of comparing information and also to develop

meaningful fields of application of the results. It is not the objective of this Technical Report to inhibit the

development of ad-hoc or natural tests, but more to encourage their development, while at the same time

increasing their scientific value.
© ISO 2009 – All rights reserved v
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TECHNICAL REPORT ISO/TR 15658:2009(E)
Fire resistance tests — Guidelines for the design and conduct
of non-furnace-based large-scale tests and simulation

CAUTION — The attention of all persons concerned with managing and carrying out this fire

resistance test is drawn to the fact that fire testing may be hazardous and that there is a possibility

that toxic and/or harmful smoke and gases can be evolved during the test. Mechanical and operational

hazards may also arise during the construction of the test elements of structures, their testing and

disposal of test residues.

An assessment of all potential hazards and risks to health shall be made and safety precautions shall

be identified and provided. Written safety instructions shall be issued. Appropriate training shall be

given to relevant personnel. Laboratory personnel shall ensure that they follow written safety

instructions at all times.
1 Scope

This Technical Report specifies procedures for the design, performance and reporting of fire tests which are

not performed using standardized test equipment, such as furnaces or test chambers, and which are primarily

duration- or time-based.

It is applicable to all “natural” fire tests, which set out to evaluate the behaviour of structural frames, rooms (or

a suite of rooms forming part of a building), with respect to fully developed fire conditions, regardless of

whether or not the heat input is by means of natural sources, e.g. cribs or burners. It is not applicable to

“reaction-to-fire” large-scale tests, which are primarily designed to evaluate materials and for which the

heating rate is slower and the maximum rate of heat release is lower than that which would occur at full

development.

In the context of this Technical Report “large” means tests in which the flame has a width of 1 m or more.

This Technical Report is intended for use by the designers of fire tests (laboratories, regulatory authorities and

researchers) and for those responsible for disseminating the information and applying the results in practice.

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.
ISO 13943, Fire safety — Vocabulary
3 Terms and definitions

For the purposes of this document, the terms and definitions given in ISO 13943 apply.

© ISO 2009 – All rights reserved 1
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ISO/TR 15658:2009(E)
4 Test design requirements
4.1 General

The difficulties experienced when testing “large” structures, e.g. space, cost, instrumentation and material

handling equipment, often cause a desire to scale down the construction being tested. In fire testing, this is

difficult because the response of the members forming part of a construction varies considerably as a result of

their mass. The thermal inertia of an element is a major influence on its thermal response. Similarly, when

direct heating is used in an experiment, such as an item or items of furniture, timber cribs, or even gas burners,

the size of the flame and the convective plume cannot meaningfully be scaled down commensurate with any

proposed reduction in volume of the test chamber or the elements forming it. Reducing the size of the test

assembly is often not an option when performing such tests. Where the experiment has to be scaled down in

size and where it can be demonstrated that the influence on the thermal response of the structure can be

quantified, the largest influence that a reduction in size has is in respect of the time at which critical events

happen. When reducing the size of an enclosure the behaviour is modelled more accurately if the heat losses

can be made to reflect the actual conditions relative to the volume/area of the space. Any such change shall

be quantified and recorded.

Before commencing the design or construction of a test assembly, it is important for the designers to identify

the objectives of the experiment as, in many cases, they define the scale and size of the construction being

evaluated. The objectives shall form part of the test report.

When designing and setting up an experiment involving a large-scale fire test, there are a number of test

parameters capable of influencing the results of the test significantly. Many of these influences can be avoided

if sufficient thought is given to the parameter when planning an experiment. If unavoidable, the influence can

be anticipated and hence compensated for when performing the test and analysing the results. Guidance on

the possible influence of these factors is given in 4.2 to 4.9.

The outcome of the analysis and the selection of the parameters used shall form part of the test

characterization and shall be reported as proposed in 7.2.
4.2 Ambient environmental conditions
4.2.1 Air currents, magnitude and direction

Air movement around the construction, which either contains the fire or is the subject of the analysis, can

seriously influence the experiment and the results obtained. Air flow directly onto ventilation apertures can

produce a pressure within the cell or room which can influence the rate at which gases may egress through

gaps or apertures, possibly having a scouring effect. Air flow across or away from such a ventilation opening

can create a vacuum on that face drawing gases out and possibly affecting the rate of burning due to a

shortage in the supply of oxygen.

Whilst still air produces the most neutral conditions, it is not easy to provide this for large-scale experiments

due to the lack of buildings able to house fire tests of this size. Equally, still air conditions are not

representative of the in-use conditions, where winds or draughts exist 90 % of the time.

The ambient air movement conditions used in the test should be justified, whether still or moving, and if

moving, the velocity and direction shall form part of that analysis.
4.2.2 Temperature

Ambient temperature affects the time at which any temperature-sensitive material reaches its critical

temperature, whether that is an ignition temperature or a phase change. If the ambient temperatures are

unusually low, these temperatures are reached after an unrealistically long time, whereas if they are high, they

can be reached unexpectedly early. The greater the mass of the temperature-sensitive material, the slower is

the thermal response. In an anticipated chain reaction, i.e. spread of fire from one object to another, the

influence of temperature is compounded, each phase being influenced independently.

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ISO/TR 15658:2009(E)

The ambient temperature, not only at the beginning of the test, but for a period prior to the test, which is

related to the thermal inertia of the materials, shall be justified and related to the anticipated in-use conditions.

Where in practice a wide range of temperatures can be expected, for instance from −5 °C to +40 °C, it can be

necessary to perform separate tests at each end of the anticipated scale, if the influence cannot be readily

modelled. If it can, a mean temperature should be used.
4.2.3 Humidity

The humidity of the air affects the moisture content of low-mass hygroscopic materials, which may influence

their propensity to ignite and burn, if they form part of the construction being evaluated. Similarly, high

moisture content and humidity can directly affect the characteristics of heat transfer and it is important to take

the prevailing conditions into account when analysing the results.

When timber (or other forms of cellulosic material) is being used as the fuel source, the moisture content

affects the rate of heat release. Guidance on this subject can be found in the Loss Prevention Council Report

[6]

TE 91338-40 . All fuel timber should be controlled to the required moisture content right up until the time of

the test.
4.3 Size of the test assembly
4.3.1 Justification for shape

The shape (numbers of sides forming the enclosures) of a test room influences the response of the structure

to fire. If the product is to be used in rectangular spaces only, this is probably the correct way of testing. If

other applications exist, i.e. for cylindrical or spherical constructions, the application of the result produced in a

rectangular test arrangement should be considered and justified when it is used in areas with a differently

shaped boundary. It is common in any heating experiment for boundary layers to become established on

surfaces, particularly in the corners of rooms or where there is a change in geometry which influences the

heat exchange on these surfaces. This influence should be analysed and allowed for when applying the

findings to structures with other shapes, e.g. curvilinear.
4.3.2 Justification for height

The height of a test chamber probably has a greater influence on the fire dynamics and response of the

structure than any other parameter. Because fire spread is initially a vertical phenomenon, the inclusion of any

ceiling, roof or horizontal closure (lid) causes the fire to spread laterally. Combustion gases rising as a result

of convective air currents cool due to the dilution with air, which becomes entrained into the plume and also

transfer heat to the environment as the height increases. As a consequence, the position of a horizontal

membrane determines the temperature of the gases when they start to spread laterally. This can influence the

temperature and depth of boundary layers, which can significantly change the feedback to other items of fuel

in the space.

It is important that the height of the ceiling/roof/horizontal membrane be considered in the light of the influence

it can have on the development of the fire conditions. The height used shall be related to the in-use conditions,

in respect of the fire load as well as its size and position. The height from the top of the heat source to the

ceiling is important in fire growth models as it influences the plume behaviour and the radiative feedback from

the gas layer. The height of the ceiling above the floor is important if flame impingement is anticipated in

practice.
4.3.3 Justification for width and depth

While the height of the test assembly is the primary influence on the response of the structure with respect to

convection (see 4.3.2), the width and depth of the chamber influence the response of the structure to radiation.

The proximity of the walls to the heat source can produce dramatically different findings if they are receiving

an unrealistically high flux relative to the hazard being reproduced. Because of the rate at which radiation

intensity decays with distance, the horizontal distances between the heat source and heated surfaces is not

as critical as the height, because there is no convective component in the heat trawler horizontally. Where the

relationship between ignition/fire source and the perimeter of the chamber is known to have an influence, the

test assembly should be related to the scenario being evaluated.
© ISO 2009 – All rights reserved 3
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ISO/TR 15658:2009(E)
4.4 Construction of the test assembly
4.4.1 Physical characteristics of elements not forming part of the test specimen

The test assembly can consist of an assembly of the elements which are the subject of the test or can consist

of a number of fixed elements forming part of a test rig to which are attached the element or elements which

are being evaluated. These fixed elements provide the methods of supporting the test specimens or providing

fixity and/or restraint. As such their physical characteristics are important, especially at the test temperature.

The critical physical characteristics of the testing that shall be justified are:

a) the material type, thickness and density of the fixed elements;
b) hot strength/load-bearing capacity;

c) the effectiveness of the fixings available for the attachment of the test specimens;

d) the quality and nature of the seal which can be provided between the rig and the specimen.

4.4.2 Thermal characteristics of elements not forming part of the test specimen

The thermal characteristics of elements only used to close off the test construction can play an important role

in creating the exposure conditions of the specimen. Where the specimen conditions of use are known, e.g. a

composite floor on top of an otherwise stone or concrete room structure, non-specimen elements used in the

test assembly should replicate these. If they do not replicate the in-use construction, any variation shall be

justified. The justification should consider the following parameters:
a) combustibility;

b) thermal diffusivity, α, where α = k/ρc with k is thermal conductivity, ρ is density and c is specific heat.

Thermal diffusity, α, provides a means to measure a material's ability to conduct thermal energy relative

to its ability to store thermal energy. Materials with a larger thermal diffusity, α, should respond to thermal

changes more quickly than materials with a smaller thermal diffusivity, α;
c) coefficient of expansion;
d) propensity to bow (due to temperature differentials).

Where the in-use conditions are not known, any test report should fully characterize these parameters to aid

subsequent analysis.
4.4.3 Attaching the specimen to the test construction

The method of fixing any single element to the adjacent structure can influence its thermal response. If the

end use is known, the method of attachment should reflect that as far as is practical. When the end use in

practice is not known, the fixing method should be fully characterized, describing:

a) the type of fixing;
b) the materials from which the fixings are made;
c) the frequency of fixings;
d) any measured torque forces, if fixings are screwed;

e) any critical temperatures related to the effectiveness of the fixing material, if non-mechanical fixings are

used.
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ISO/TR 15658:2009(E)

In the case of load-bearing assemblies, the levels of fixing and restraint should be quantified and where

possible related to the actual levels of restraint expected.
4.4.4 Sealing of the specimen into the test structure

The sealing of the specimen into the test structure is normally only critical if the test assembly is being

evaluated for its ability to contain fire spread. However, if an edge member is to be evaluated for load-bearing

capacity, the seal may influence just how much of that member is heated. When the seal does not represent

the in-use condition, the material and method chosen shall be justified and the seal should be fully

characterized with respect to the following characteristics:
a) the dimensions, particularly the depth in the case of a linear gap seal;
b) the composition/nature of the material;
c) its physical state, e.g. rigid, flexible or compressible;

d) any known thermal characteristics, e.g. softening temperature, activation temperature and expansion ratio

(in the case of heat-activated materials).
4.5 Test specimen
4.5.1 Construction of the test specimen

It is assumed that most of the test specimen is manufactured/constructed as it would be when in use, as this

is presumably the subject of the test. However, for purposes of practicality, it may be necessary to introduce

additional or non-representative joints. When introducing such joints the influence of the joint on the following

parameters shall be considered:
a) heat transfer between elements and through the element;
b) the integrity of the specimen;
c) the thermal expansion and distortion of the specimen;
d) the transfer of load, both applied and thermally induced.

When the jointing incorporates seals, these should be characterized as proposed in 4.4.4.

4.5.2 Materials for the test specimen

The selection of the materials used for the test specimen shall replicate those in the element to be used.

However, when constructing specimens for the test it shall be recognized that some of the materials are out of

balance with those used in practice as a result of the time they have to age or condition. Time should be

allowed for them to achieve equilibrium with the environment and unless impossible, also to achieve the same

state of cure as in practice. If it is impractical to achieve either, the difference between the tested condition

and the actual condition should be determined. Non-homogeneous materials should be made in as similar a

manner as possible to those being duplicated. The factors that shall be justified are:

a) the moisture content (for hygroscopic materials);
b) the curing for hydraulic-based materials;
c) the chemical reaction for compounds;
d) the strength of any bonding materials/adhesives.
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ISO/TR 15658:2009(E)
4.6 Selection of heating conditions
4.6.1 Fire exposure

This is the most critical of the test parameters as the selection of the wrong heating conditions can effectively

render the experiment/test valueless. It shall be recognized that in most cases, the conditions used in the test

can only represent one scenario of all those possible and therefore the heating conditions shall be correctly

specified and reproduced. If more than one common scenario is likely, multiple testing can be necessary.

As a result, the selection of the heating conditions shall be fully justified in respect of the following:

a) the total heat release;
b) the ratio of convective and radiant heat;
...

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