ISO/TR 13571-2:2016

TECHNICAL ISO/TR
REPORT 13571-2
First edition
Life-threatening components of fire —
Part 2:
Methodology and examples of
tenability assessment
Composants dangereux du feu —
Partie 2: Méthodologie et exemples d’analyse de tenabilité
PROOF/ÉPREUVE
Reference number
ISO/TR 13571-2:2016(E)
©
ISO 2016

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ISO/TR 13571-2:2016(E)

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ISO/TR 13571-2:2016(E)

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 1
5 Performance criteria . 3
6 Evaluation of the impact . 3
6.1 Effects of fire on people . 3
6.2 Models for toxic impact . 3
6.3 Models for thermal impact . 4
6.3.1 Radiant flux exposure model . 4
6.3.2 Temperature exposure model . 4
6.3.3 Dose calculation model . 4
7 Examples of application . 4
Annex A (informative) Example of application to real-scale fire scenarios - FED and ASET
calculations for fire experiments conducted in a full-scale test house under two
basement fire scenarios . 6
Annex B (informative) Example of application to real-scale fire scenarios - FED calculations
for fire experiments conducted in a full-scale test of single sleeping rooms .20
Annex C (informative) Methodology for application of ISO 13571 in Fire Safety
Engineering approach .41
Annex D (informative) Example of application to Fire Safety Engineering–Case Nr 1 – hotel
room and corridor .51
Annex E (informative) Example of application to Fire Safety Engineering – Case Nr 2
– restaurant .64
Annex F (informative) Determination of data for matrix .81
Bibliography .84
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ISO/TR 13571-2:2016(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 procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).
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. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www.iso.org/patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation on the meaning of ISO specific terms and expressions related to conformity assessment,
as well as information about ISO’s adherence to the World Trade Organization (WTO) principles in the
Technical Barriers to Trade (TBT) see the following URL: www.iso.org/iso/foreword.html.
The committee responsible for this document is ISO/TC 92 Fire Safety, Subcommittee 3, Fire threat to
people and the environment.
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ISO/TR 13571-2:2016(E)

Introduction
Tenability of people in case of fire is an essential safety objective of regulations. Reasons that could lead
to compromised tenability conditions are loss of visibility, thermal and toxic effects. ISO 13571 is a tool
that has been developed to quantify the performance level related to these criteria in case of a fire.
This document presents application cases of ISO 13571. It is structured as follows:
— Clause 4 explains the principle of the application;
— Clause 5 presents the selection of performance criteria;
— Clause 6 presents the evaluation of the impact of fire to people according to ISO 13571;
— Clause 7 introduces the examples detailed in Annexes A, B, D and E.
Examples of application are presented in annexes. The first case of application concerns comparison
of tenability in real-scale fire tests (Annex A and Annex B). The second case presents the methodology
(Annex C) and two example cases (Annex D and Annex E) for application of ISO 13571 as performance
criteria in Fire Safety Engineering studies according to ISO 23932. Annex F presents information on
experimental production of input data.
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TECHNICAL REPORT ISO/TR 13571-2:2016(E)
Life-threatening components of fire —
Part 2:
Methodology and examples of tenability assessment
1 Scope
This document describes the practical application of ISO 13571 as a tool to evaluate effects of fire
effluents on people. The method of application, performance criteria and evaluation of the impact are
explained and illustrated by two families of examples: application to real-scale tests (Annex A and
Annex B) and application to Fire Safety Engineering (Annex C, D and E).
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and are
indispensable for its application. For dated references, only the edition cited applies. For undated
references, the latest edition of the referenced document (including any amendments) applies.

There are no normative references in this document.
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 13943 and ISO 13571
apply. ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
— IEC Electropedia: available at http://www.electropedia.org/
— ISO Online browsing platform: available at http://www.iso.org/obp
4 Principle
Smoke toxicity, to a certain degree, is not a material property. Depending on the environment,
availability of oxygen, thermal attack, flow conditions and surface areas available for combustion, the
chemistry of the combustion of a given material can proceed along various routes and produce species
[1][2][3]
in very different quantities. It is then a systemic parameter, which need a systemic approach, as
stated in ISO 19706.
It is also appropriate to keep the following points in mind:
— The production rates of various gaseous species change according to the combustion regime. In
particular the influential parameters (not exhaustive) are:
— Fuel nature
— Oxygen availability
— Temperature
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— Flows received and lost
— The species produced by the combustion are carried away from the initial fire source, and their
effect is related to:
— Sensitivity and activity of people
— Concentrations (instantaneous)
— Exposure times (accumulation)
Furthermore, the thermal effects related to the heat of the gases and smoke produced, along with the
radiant fluxes, which they emit, play a role in the safety of people who are evacuating.
For a given design fire, it is therefore necessary to determine one or more exposure scenarios, which
will make it possible to answer questions about the effects on people according to:
— The fire source and its development;
— The species produced by this fire source and their movement away from the original fire source;
— The evacuation of the people, their path and the toxic and thermal elements to which they are subject
as a function of time.
Finally, it is useful to recall that toxic hazard in enclosures is mainly caused by the combustion of the
contents and furnishings in the enclosure rather than the enclosure itself in the early phases of a fire.
Furthermore, changes in regulations can lead to better insulation of the rooms, modification of the
ventilation, and resistance of windows to bursting, all of which notably change the conditions for the
accumulation of thermal energy and the generation of toxic species.
The following are the objectives of the application of ISO 13571:
— Assess effects of fire on people as a principal criterion for performance evaluation in Fire Safety
Engineering studies, or in comparison of real-scale fire tests,
— Involve realistic fire sources in terms of:
— Kinetics
— Species produced, in particular by including data concerning the toxic species related to the
burning of the contents and furnishings in building fires
— Be able to process all the materials present and not just certain ones
— Consider all potential toxic species, not only CO, as is often seen in practice
— Consider the aspects of production kinetics, movement of gases, and availability of oxygen
— Be able to process several scenarios and their possible variations:
— “Typical” materials/”risky” materials
— Risk in the room of fire origin room and outside the room of origin
— Different fire regimes (smouldering, well ventilated, post-flashover)
— Evacuation plans
— Consider the various risks for people and the associated sanction criteria as a function of thermal
and toxic effects, both instantaneous and by accumulation.
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5 Performance criteria
The selection of criteria to consider is conducted in early phases of a project, before any detailed study.
These criteria will make it possible to determine whether a given exposure scenario (i.e. a fire scenario
combined with an evacuation scenario) is a success or failure. This concept depends above all on the
susceptibility of the people to the fire effluent. In the application of ISO 13571, the objective that a
person could realize his/her own evacuation without any assistance.
In fact, each person is different and according to their constitution, age, gender, possible underlying
conditions, etc. the FEC and FED which they can endure before being incapacitated varies. There is,
however, no feedback from experience which can be used in statistical terms. Due to the lack of precise
knowledge in this field, approximating the distribution of individual susceptibilities by a log-normal
distribution with a median value of one as thresholds for the FED and FEC is proposed. Half the
population is therefore considered as being able to tolerate FED and FEC each having a value of one, and
the other half is more sensitive and cannot tolerate values of FED and FEC equal to or above one.
As an example of a safety criterion that provides protection for a larger fraction of the population,
ISO 13571:2012, A.5.2 shows that a value 0,3 protects a significant portion of the more sensitive people.
At this value, 11,4 % of the population remains vulnerable to incapacitation by exposure to the fire
effluent. It should be kept in mind that one of the consequences of the distribution described by the
ISO 13571:2012 standard for the sensitivity of individuals (log-normal law) is that there is no value for
the criterion which is low enough to guarantee protection of all occupants in an evacuation situation.
Designing a facility such that the FED and FEC values are kept to extremely low values is likely to require
immediate detection and suppression or to preclude otherwise desirable construction and furnishing
products. It is the regulator’s role to weigh these considerations.
6 Evaluation of the impact
6.1 Effects of fire on people
The impact of fire effluent on a person depends on two interacting components. The first is the location
of a person and how that location might change during the course of the fire. The second is the evolving
concentrations of the effluent constituents where the person is located.
A fire safety assessment could be made considering the evolution of tenability for a person who is
stationary at one position in a room. This would apply to people who are asleep or medically confined.
Such an application in real-scale fire tests is presented in Annex A. Assessment could also consider the
exposure of a person moving along an egress path with its travel path in real-scale fire tests (Annex B)
or included in a Fire Safety Engineering approach (Annexes C to E).
The exposure models used are those described in ISO 13571:2012. In particular, they cover the toxic and
thermal models, but do so independently. For the toxic models, the effects of the asphyxiating and irritating
gases are considered separately. See ISO 19706 for more details on the relevance of these models.
6.2 Models for toxic impact
Toxic effluents can have two principal mechanisms of action on people when considering acute
exposure. Depending on their nature, they are classified into two categories:
— asphyxiating gases (CO, HCN, etc.)
— irritating gases (HCl, HBr, etc.)
There are also indirect effects like those of the low oxygen concentration (hypoxia) or high CO
2
concentration (hyperventilation). Other effects exist, like clogging of the respiratory tracts because of
the presence of soot.
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The evaluation of the effects related to exposure to smoke requires knowledge of the central concepts.
[4] [5]
The References and present a review of the art of these concepts.
Because of the complexity of the problem, there are various models incorporating toxic effects.
Although all of them can be used, a first consensus was established on the models given in ISO 13571.
In the ISO 13571 models, the asphyxiating gases, incorporated using the calculation of a Fractional
Effective Dose (FED), and the irritating gases, incorporated using the calculation of Fractional Effective
Concentration (FEC), are considered separately.
Thus, the asphyxiating gases (mainly CO, and HCN) are considered from the perspective of an
accumulation mechanism, and the irritants (mainly HCl, HBr, HF, SO , NO, NO , acrolein, and
2 2
formaldehyde) from that of their instantaneous effect. These assumptions are only valid when
considering short-term acute effects at an incapacitating level of exposure. For irritants, other, dose-
related aspects need to be included when considering long exposures or lethality levels.
One of the limits of the ISO 13571 asphyxiant gas model is that it does not incorporate the rarefaction
of oxygen, O , which also has an asphyxiating effect. However, in many situations this effect can be
2
considered to be minor compared with the effects of CO and HCN. CO is considered as producing a
2
hyperventilation factor in ISO 13571.
6.3 Models for thermal impact
Three mechanisms are considered: hyperthermia linked to exceeding the body’s thermal regulation
capacity, skin burns, and burns in the bronchial tubes. In most cases, bronchial tube burns take place at
higher exposure levels than skin burns.
There are two models proposed in ISO 13571 one for radiant flux exposure and one for exposure
to convective heat exchange – and they are synthesized in the form of an FED making it possible to
calculate the cumulative dose.
6.3.1 Radiant flux exposure model
Two formulas are proposed in ISO 13571. The first makes it possible to calculate the time to get second-
degree burns on the skin; the second makes it possible to calculate the time to reach the pain threshold.
It should be noted that the skin temperature depends on the applied flux density at the surface and the
ease with which the blood carries away the energy reaching under the skin. Because of this there is a
−2
threshold located around 2,5 kW.m , below which exposure to the flux does not cause a significant
temperature increase of the skin and above which the temperature increase occurs quickly. A greater
exposure can however be acceptable with the exposure time is short, especially when considering
passing before an opening leading to an area on fire. Further details can be found in ISO 13571.
6.3.2 Temperature exposure model
Two formulas are included in ISO 13571, according to whether the subject is dressed normally or
lightly dressed (even naked) for calculating the time necessary to become incapacitated (for an air
environment at less than 10 % relative humidity).
6.3.3 Dose calculation model
The dose effect linked to the accumulation of the temperature is calculated using the thermal model
FED equation of ISO 13571.
7 Examples of application
Annex A presents an example of application of ISO 13571 to a series of real-scale fire tests performed on
houses with different designs of floors between the basement and the rest of the house, in two different
basement fire scenarios. The objective of the study was to better understand the impact of basement
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fires on the ability of occupants on the upper storeys to escape. ISO 13571 models are used to monitor
tenability conditions at various locations in the upper storeys. The example gives a relative comparison
between different designs, using FED as the comparison criterion, without considering any specific
evacuation scenario.
Annex B presents the application of ISO 13571 to different real-scale fire scenarios on a single sleeping
room. Analysis is based on the time to reach compromised tenability conditions using thermal and
toxic models of ISO 13571 and different evacuation strategies. The results identify the main factor
comprising tenability for each scenario, according to occupant’s behaviour.
Annex C presents a methodology to apply ISO 13571 to Fire Safety Engineering studies. It refers to
ISO 23932 and proposes a mathematical approach that allows obtaining tenability data as performance
criteria. This methodology is based on a construction of a source term of toxic gases in addition to a
source term of heat release in the Design Fire Scenario studied. It proposes ways to obtain data for each
fire stage and presents the input data in a matricial shape.
Annex D is a first application of methodology proposed in Annex C. The situation is a fire in a hotel room
connected to a corridor equipped with mechanical smoke control devices. Tenability assessment in the
corridor is studied according to the ISO 13571 models. Various scenarios of occupant behaviour are
tested, such as different departure times, a travel trough the corridor or turn back depending on the
conditions. The different evacuation strategies and occupant behaviour lead to contrasted results: in
some scenarios, tenability is driven by thermal effects, and in some other, toxic effects prevails.
Annex E is a second application of the methodology proposed in Annex C. The situation is a fire in a
restaurant equipped with natural smoke control openings and an operating heating, ventilating, and air
conditioning (HVAC) system. The fire starts in a hidden technical room (dishwashing room). Tenability
assessment is performed along two escape routes, considering various pre-movement delays. The
different evacuation strategies and occupant behaviour lead to contrasted results: depending on route
chosen and pre-movement delay, tenability is driven by either thermal effects or toxic effects. Results
are also expressed as success (FED, FEC < 0,3) versus pre-movement delay.
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Annex A
(informative)

Example of application to real-scale fire scenarios - FED and ASET
calculations for fire experiments conducted in a full-scale test
house under two basement fire scenarios
A.1 General
An experimental program was undertaken to study the fire performance of various engineered floor
systems used in single-family houses as construction moves away from the traditional solid sawn
[6]
wood joists . The experimental program was conducted using a test facility representing a two-storey
detached single-family house with a basement (referred to as the test house hereafter). It involved full-
scale fire experiments with unprotected floor assemblies located over the basement (unsheathed on
the basement side) using two specific basement fire scenarios. The objective of the study was to better
understand, from the perspective of tenability and structural integrity of the floor assemblies as egress
routes, the impact of basement fires on the ability of occupants on the upper storeys to escape.
The experimental program used a timeline approach to establish the sequence that affects the life
safety and egress of occupants under two specific basement fire scenarios. This sequence included
fire initiation, smoke alarm activation, onset of untenable conditions on upper storeys, and structural
failure of the test floor assembly as a viable egress route on the first storey. The experimental approach
was designed to determine how long egress routes would remain viable from the perspective of both
tenability and structural integrity of the test floor assembly. With the use of engineered joists and
trusses in floor construction, it is desirable that the time to incapacitation of occupants should not be
adversely affected. Structural failure of the floors constructed with alternative engineered products
should not occur prior to the time taken to reach incapacitating levels of smoke, gases and heat. This
involved FED and ASET calculations using experimental data and comparison between ASET and the
floor failure time.
A.2 Experiments
Brief descriptions of the experiments are provided in the following sections. Further details of the
[6]
experimental setup can be found in reference .
A.2.1 Facility
2
Each storey of the test house had a floor area of 95 m and a ceiling height of 2,4 m. The basement
2
was partitioned to create a fire compartment representing a 27,6 m basement living area; the
remaining area was not used during the experiments. The fire compartment had a rectangular exterior
opening (2,0 m wide by 0,5 m high) covered with a removable non-combustible panel. The walls of
the fire compartment were lined with 12,7 mm thick regular gypsum board. The gypsum board met
ASTM C1396 and CAN/CSA-A82.27 material standards and consisted of a solid set gypsum core enclosed
2
in face paper and liner back paper with a weight of 7,8 kg/m , a Flame Spread rating of 15 and Smoke
Developed rating of 0 in accordance with ASTM E84 (UL 723, UBC 8-1,NFPA 255, CAN/ULC-S102). An
enclosed stairwell connected the fire compartment to the first storey. At the top of this stairwell, a
0,81 m wide by 2,05 m high doorway led to the first storey. This doorway either had a door in the closed
position (closed basement doorway) or had no door at all (open basement doorway), depending on the
scenario being studied.
The first storey had an open-plan layout with no partitions. A test floor assembly was constructed on the
first storey directly above the basement fire compartment for each experiment. A range of engineered
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floor systems, including wood I-joist, steel C-joist, metal plate wood truss and metal web wood truss
assemblies as well as solid wood joist assemblies were used in the full-scale fire experiments. A 0,89 m
wide by 2,07 m high doorway led to the exterior. The staircase to the second storey was not enclosed.
The second storey had a corridor (measuring 4,45 m long by 1,10 m wide) and bedrooms. Two bedrooms
2
(each having a floor area of 16,8 m ) were used as target bedrooms in the experiments. The door to one
of the bedrooms was kept open whereas the door to the other bedroom remained closed. Each bedroom
doorway was 0,81 m wide by 2,05 m high.
A.2.2 Fire scenarios
Two fire scenarios were used in the full-scale fire experiments:
— the doorway from the first storey to the basement had no door (referred to as the open basement
doorway scenario);
— a hollow-core interior door was used in the doorway in the closed position (referred to as the closed
basement doorway scenario).
A simple and repeatable fuel package was developed for use in full-scale experiments to fuel a fire that
simulated a basement living area fire. This fuel package consisted of a mock-up sofa constructed with
9 kg of flexible polyurethane foam without any upholstery fabric, and 190 kg of wood cribs beside and
underneath the mock-up sofa. The polyurethane blocks used were furniture grade flexible foam with
3
a chemical formula of CH O N and a density of 32,8 kg/m . The fuel package was located
1,91 0,263 0,055
at the centre of the fire compartment in order to provide a greater challenge to the unprotected floor
[7]
assemblies above. The mock-up sofa was ignited in accordance with the ASTM 1537 test protocol
and the w
...