ISO/FDIS 13571-5

• Abstract:

  This documents deals with mass loss model, heat and radiant energy model, and smoke obscuration model

• Status: Not Published
• ICS: 13.220.01 - Protection against fire in general
• Technical Committee: ISO/TC 92/SC 3 - Fire threat to people and environment
• Drafting Committee: ISO/TC 92/SC 3/WG 5 - Prediction of toxic effects of fire effluents
• Current Stage: 5020 - FDIS ballot initiated: 2 months. Proof sent to secretariat
• Start Date: 21-Aug-2026
• Completion Date: 21-Aug-2026

Overview

ISO/FDIS 13571-5: Life-threatening components of fire - Part 5: Heat, smoke obscuration and mass loss models is an international standard developed by ISO Technical Committee 92, Subcommittee 3 (ISO/TC 92/SC 3). This standard provides a structured approach for assessing key hazards in fire environments that can threaten human life, focusing specifically on heat exposure, smoke obscuration, and toxicity related to material mass loss.

The document sets out simplified models and criteria for evaluating the tenability of building occupants and rescue scenarios in fires. It guides fire safety professionals, engineers, and regulators in estimating the point at which exposed individuals may no longer be able to accomplish safe self-evacuation or escape due to heat, impaired visibility from smoke, or toxic fire gases.

Key Topics

• Heat Exposure Models

  • Considers the effects of radiant and convective heat on the human body.
  • Addresses critical thresholds for skin burns and hyperthermia linked to loss of mental function.
  • Discusses cumulative impacts of radiation and convection and their contributions to compromised tenability.

• Smoke Obscuration Models

  • Focuses on the reduction of visibility due to smoke aerosol concentration.
  • Provides guidance for threshold concentrations that lead to disorientation and hindered evacuation.

• Mass Loss Toxicity Models

  • Introduces a simplified life-threat assessment based on the mass loss of burning materials.
  • Links mass loss data to toxic potency, allowing for estimation of exposure risk in the absence of detailed gas concentration measurements.

• Tenability Criteria

  • Defines practical endpoints (known as tenability limits) for heat, smoke, and toxic exposure beyond which occupants cannot take effective action for escape.
  • Uses the shortest time to compromised tenability among the different hazards as the critical value for safety assessment.

Applications

ISO/FDIS 13571-5 is highly relevant for the following fire safety engineering and regulatory scenarios:

• Building and Infrastructure Design

  • Used to evaluate fire safety strategies and material choices in new and existing structures.
  • Supports development and verification of evacuation models and safety plans.

• Fire Safety Engineering Analysis

  • Assists engineers in simulating fire development and its impact on occupant survivability.
  • Informs decisions about the adequacy of fire protection systems, such as detection and suppression technologies.

• Risk Assessment and Regulatory Compliance

  • Provides a scientific basis for life safety assessments required by authorities having jurisdiction.
  • Supports compliance with building codes and fire safety standards around occupant protection.

• Product Testing and Material Selection

  • Utilized in evaluating and comparing the fire performance of construction materials and products under well-ventilated and under-ventilated fire conditions.
  • Assists manufacturers in demonstrating conformity to international fire safety benchmarks.

Related Standards

Professionals applying ISO/FDIS 13571-5 should also consider these connected international standards:

• ISO 13571-1: Guidelines for estimation of time to compromised tenability and escape capability in fires - Method A.
• ISO 13571-3: Guidelines for estimation of time to compromised tenability and escape capability in fires - Method B.
• ISO 13344: Estimation of the lethal toxic potency of fire effluents.
• ISO 19706: Guidelines for assessing the fire threat to people.
• ISO 29904: Fire chemistry - Generation and measurement of aerosols.
• ISO 13943: Fire safety - Vocabulary.

By integrating ISO/FDIS 13571-5 with these related standards, fire safety professionals can achieve a comprehensive and robust assessment of fire life safety in diverse environments.

Keywords: ISO 13571-5, fire safety, heat exposure, smoke obscuration, mass loss model, occupant tenability, toxicity, evacuation modeling, international fire standards, hazard assessment, fire effluent, building safety.

FINAL DRAFT
International
Standard
ISO/TC 92/SC 3
Life-threatening components of
Secretariat: AFNOR
fire —
Voting begins on:
2026-08-21
Part 5:
Heat, smoke obscuration and mass
Voting terminates on:
2026-10-16
loss models
Composants dangereux du feu —
Partie 5: Modèles de chaleur, d'obscurcissement dû à la fumée et
de perte de masse
RECIPIENTS OF THIS DRAFT ARE INVITED TO SUBMIT,
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RELEVANT PATENT RIGHTS OF WHICH THEY ARE AWARE
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BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO-
LOGICAL, COMMERCIAL AND USER PURPOSES, DRAFT
INTERNATIONAL STANDARDS MAY ON OCCASION HAVE
TO BE CONSIDERED IN THE LIGHT OF THEIR POTENTIAL
TO BECOME STAN DARDS TO WHICH REFERENCE MAY BE
MADE IN NATIONAL REGULATIONS.
Reference number
FINAL DRAFT
International
Standard
ISO/TC 92/SC 3
Life-threatening components of
Secretariat: AFNOR
fire —
Voting begins on:
Part 5:
Heat, smoke obscuration and mass
Voting terminates on:
loss models
Composants dangereux du feu —
Partie 5: Modèles de chaleur, d'obscurcissement dû à la fumée et
de perte de masse
RECIPIENTS OF THIS DRAFT ARE INVITED TO SUBMIT,
WITH THEIR COMMENTS, NOTIFICATION OF ANY
RELEVANT PATENT RIGHTS OF WHICH THEY ARE AWARE
AND TO PROVIDE SUPPOR TING DOCUMENTATION.
© ISO 2026
IN ADDITION TO THEIR EVALUATION AS
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO-
LOGICAL, COMMERCIAL AND USER PURPOSES, DRAFT
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
INTERNATIONAL STANDARDS MAY ON OCCASION HAVE
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
TO BE CONSIDERED IN THE LIGHT OF THEIR POTENTIAL
or ISO’s member body in the country of the requester.
TO BECOME STAN DARDS TO WHICH REFERENCE MAY BE
MADE IN NATIONAL REGULATIONS.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland Reference number
ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3  Terms and definitions . 1
4 Heat . 1
4.1 Heat exposure pathways .1
4.2 Radiation .2
4.3 Convection .2
4.4 Radiation and convection cumulative consequences .3
4.5 Tenability limit .3
5 Smoke-obscuration model . 3
6 Mass loss model for toxicity assessment of combustion gases . 5
Bibliography . 7

iii
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 document 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).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, 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 www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 92 Fire safety, Subcommittee 3, Fire threat to
people and environment.
A list of all parts in the ISO 13571 series can be found on the ISO website.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.

iv
Introduction
The ISO 13571 series is a set of International Standards developed for estimation of time to compromised
tenability and escape capability for occupants when exposed to a fire environment. Different threats are
evaluated separately for exposure to acute toxicants, heat and smoke. Potential interactions between the
different threats have not been addressed in the ISO 13571 series.
Therefore, the time to compromised tenability is taken as the shortest of the determined times to
compromised tenability from each of the different threats.
This guidance can also be applied to estimation of the time limit for rescuing people who are immobile due to
injury, medical condition, etc. This document establishes procedures to evaluate the life-threat components
of fire hazard analysis in terms of the status of exposed human subjects at discrete time intervals. It makes
possible the estimation of a tenability endpoint, at which time it is estimated that occupants are no longer
able to take effective action to accomplish their own escape. It enables estimation of a tenability endpoint for
each of the fire effluent components, with the most important endpoint being the earliest to occur.
Although occupants’ inability to accomplish their own escape is consistent with the definition of
incapacitation (see ISO 13943), this term is not used in this document due to its potentially broad
interpretation to include many effects, including collapse and unconsciousness, that are not addressed. This
document focuses specifically on taking effective action to accomplish escape as may be influenced by both
physiological and behavioural responses resulting from exposure to fire’s life threat components.
The life threat components addressed in this document include heat and visual obscuration due to smoke
together with a simplified mass loss-based model for toxicity assessment of combustibles.
Chronic health effects and environmental impacts are not covered in the ISO 13571 series.

v
FINAL DRAFT International Standard ISO/FDIS 13571-5:2026(en)
Life-threatening components of fire —
Part 5:
Heat, smoke obscuration and mass loss models
1 Scope
This document is only one of many tools available for use in fire safety engineering. It is intended to be
used in conjunction with models for analysis of the initiation and development of fire, fire spread, smoke
formation and movement, chemical species generation, transport and decay, and people movement, as well
as fire detection and suppression. This document is to be used only within this context.
This document addresses the consequences of human exposure to the heat, obscuration induced by smoke
and proposed a simplified mass loss-based toxicity model. The time-dependent thermal environment of a
fire and aerosol concentrations are determined by the rate of fire growth and the ventilation pattern. Once
these are determined, the methodology presented in this document can be used for the estimation of the
time at which individuals can no longer accomplish their own escape or reach a place of safe refuge.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes
requirements 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
ISO 13571-1, Life-threatening components of fire — Part 1: Guidelines for the estimation of time to compromised
tenability and escape capability in fires — Method A
ISO 13571-3, Life-threatening components of fire — Part 3: Guidelines for the estimation of time to compromised
tenability and escape capability in fires — Method B
3  Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 13943, ISO 13571-1 and ISO 13571-3
apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
4 Heat
4.1 Heat exposure pathways
There are three basic ways in which exposure to heat can lead to life threat:
a) hyperthermia;
b) body surface burns;
c) respiratory tract burns.
For use in the modelling of life threat due to heat exposure in fires, it is necessary to consider only two
criteria:
— threshold of second degree burning of the skin;
— exposure where hyperthermia is sufficient to cause mental deterioration and, therefore, threaten
survival.
NOTE Thermal burns to the respiratory tract from inhalation of air containing less than 10 % by volume of water
vapour do not occur in the absence of burns to the skin or the face; thus, tenability limits with regard to skin burns
are normally lower than for burns to the respiratory tract. However, thermal burns to the respiratory tract can occur
upon inhalation of air above 60 °C when saturated with water vapour.
4.2 Radiation
−2
The tenability limit for exposure of skin to radiant heat is approximately 2,5 kW·m . Below this incident
heat flux level, exposure can be tolerated for 30 min or longer without significantly affecting tenability.
Above this threshold value, the time, t , expressed in minutes, to second degree burning of skin due to
Irad
[4]
radiant heat decreases rapidly according to Formula (1) .
15, 6
tq69, (1)
Irad
where q is the radiant heat flux, expressed in kilowatts per square metre.
As with toxic gases, an exposed occupant may be considered to accumulate a dose of radiant heat over a
period of time. The FED (fractional effective dose) of radiant heat accumulated per minute is the reciprocal
of t .
Irad
NOTE Radiant heat tends to be directional, producing localized heating of particular areas of skin even though
the air temperature in contact with other parts of the body can be relatively low. Skin temperature depends upon
the balance between the rate of heat applied to the skin surface and the removal of heat subcutaneously by the blood.
Thus, there is a threshold radiant flux below which significant heating of the skin is prevented but above which quite
rapid heating occurs.
The time to experiencing pain due to radiant heat can have a behavioural effect on the time to compromised
tenability. The time, t , expressed in minutes, to experiencing pain due to radiant heat is a somewhat more
Irad
[4]
strongly inverse function of radiant heat than that for the burning of skin. It is expressed by Formula (2) .
1,9
tq 4,2 (2)
Irad
where q is the radiant heat flux, expressed in kilowatts per square metre.
Based on the above information, it is estimated that the uncertainty associated with the use of Formulae (1)
−2
and (2) is ±25 %. Moreover, an irradiance of 2,5 kW·m would correspond to a source surface temperature
of approximately 200 °C, which is most likely to be exceeded near the fire, where conditions are changing
rapidly.
4.3 Convection
4.3.1 Calculation of the time to prevention of escape under conditions of exposure to convective heat
[5]
from air containing less than 10 % by volume of water vapour can be made using either Formula (3) or
[6]
Formula (4) .
As with toxic gases, an exposed occupant can be considered to accumulate a dose of convected heat over a
period of time. The FED of convected heat accumulated per minute is the reciprocal of t .
Iconv
4.3.2 The time, t , expressed in minutes, to experiencing pain due to convective heat accumulated per
Iconv
minute depends upon the extent to which an exposed occupant is clothed and the nature of the clothing. For
[7]
fully clothed subjects, Formula (3) is appropriate :
8 36, 1
tT(4,1 10 ) (3)
Iconv
where T is the temperature, expressed in degrees Celsius.
[6]
4.3.3 For unclothed or lightly cl
...

ISO/DIS FDIS 13571-5:2025(en)
ISO/TC 92/SC 3
Secretariat: AFNOR
Date: 2025-06-022026-08-07
Life-threatening components of fire — —
Part 5:
Heat, smoke obscuration and mass loss models
Composants dangereux du feu —
Partie 5: Modèles de chaleur, d'obscurcissement dû à la fumée et de perte de masse
FDIS stage
ISO #####-#:####(X/FDIS 13571-5:2026(en)
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication
may be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying,
or posting on the internet or an intranet, without prior written permission. Permission can be requested from either ISO
at the address below or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: + 41 22 749 01 11
EmailE-mail: [e-mail]
Website: www.iso.org
Published in Switzerland
© ISO #### 2026 – All rights reserved
ii
ISO/DIS FDIS 13571-5:20252026(en)
Contents
Foreword . iv
Introduction . vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Heat . 1
4.1 Heat exposure pathways . 1
4.2 Radiation . 2
4.3 Convection . 3
4.4 Radiation and convection cumulative consequences . 3
4.5 Tenability limit . 4
5 Smoke-obscuration model . 4
6 Mass loss model for toxicity assessment of combustion gases . 6
Bibliography . 9

iii
ISO #####-#:####(X/FDIS 13571-5:2026(en)
Foreword
© ISO #### 2026 – All rights reserved
iv
ISO/DIS FDIS 13571-5:20252026(en)
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 document 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).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent rights
in respect thereof. As of the date of publication of this document, ISO had not received notice of (a) patent(s)
which may be required to implement this document. However, implementers are cautioned that this may not
represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, 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 www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 92 Fire Safetysafety, Subcommittee 3, Fire threat
to people and environment.
A list of all parts in the ISO 13571 series can be found on the ISO website.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.
v
ISO #####-#:####(X/FDIS 13571-5:2026(en)
Introduction
The ISO 13571 series is a set of standardsInternational Standards developed for estimation of time to
compromised tenability and escape capability for occupants when exposed to a fire environment. Different
threats are evaluated separately for exposure to acute toxicants, heat and smoke. Potential interactions
between the different threats have not been addressed in thisthe ISO 13571 series of standards.
Therefore, the time to compromised tenability is taken as the shortest of the determined times to
compromised tenability from each of the different threats.
This guidance can also be applied to estimation of the time limit for rescuing people who are immobile due to
injury, medical condition, etc. This document establishes procedures to evaluate the life-threat components of
fire hazard analysis in terms of the status of exposed human subjects at discrete time intervals. It makes
possible the estimation of a tenability endpoint, at which time it is estimated that occupants are no longer able
to take effective action to accomplish their own escape. It enables estimation of a tenability endpoint for each
of the fire effluent components, with the most important endpoint being the earliest to occur.
Although occupants’ inability to accomplish their own escape is consistent with the definition of incapacitation
(see ISO 13943), this term is not used in this document due to its potentially broad interpretation to include
many effects, including collapse and unconsciousness, that are not addressed. This document focuses
specifically on taking effective action to accomplish escape as may be influenced by both physiological and
behavioural responses resulting from exposure to fire’s life threat components.
The life threat components addressed in this standarddocument include heat and visual obscuration due to
smoke together with a simplified mass loss-based model for toxicity assessment of combustibles.
Chronic health effects and environmental impacts are not covered in the ISO 13571 series.
© ISO #### 2026 – All rights reserved
vi
DRAFT International Standard ISO/DIS 13571-5:2025(en)

Life-threatening components of fire — —
Part 5:
Heat, smoke obscuration and mass loss models
1 Scope
This document is only one of many tools available for use in fire safety engineering. It is intended to be used
in conjunction with models for analysis of the initiation and development of fire, fire spread, smoke formation
and movement, chemical species generation, transport and decay, and people movement, as well as fire
detection and suppression. This document is to be used only within this context.
This document addresses the consequences of human exposure to the heat, obscuration induced by smoke
and proposed a simplified mass loss-based toxicity model. The time-dependent thermal environment of a fire
and aerosol concentrations are determined by the rate of fire growth and the ventilation pattern. Once these
are determined, the methodology presented in this document can be used for the estimation of the time at
which individuals can no longer accomplish their own escape or reach a place of safe refuge.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes
requirements 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
ISO 13571--1, Life-threatening components of fire — Part 1: Guidelines for the estimation of time to
compromised tenability and escape capability in fires — Method A
ISO 13571--3, Life-threatening components of fire — Part 3: Guidelines for the estimation of time to
compromised tenability and escape capability in fires — Method B
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 13943, ISO 13571-1 and ISO 13571--
3 apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— — ISO Online browsing platform: available at https://www.iso.org/obp
— — IEC Electropedia: available at https://www.electropedia.org/
4 Heat
4.1 Heat exposure pathways
There are three basic ways in which exposure to heat can lead to life threat:
ISO #####-#:####(X/FDIS 13571-5:2026(en)
a) a) hyperthermia;
b) b) body surface burns;
c) c) respiratory tract burns.
For use in the modelling of life threat due to heat exposure in fires, it is necessary to consider only two criteria:
— — threshold of second degree burning of the skin;
— — exposure where hyperthermia is sufficient to cause mental deterioration and, therefore, threaten
survival.
NOTE Thermal burns to the respiratory tract from inhalation of air containing less than 10 % by volume of water
vapour do not occur in the absence of burns to the skin or the face; thus, tenability limits with regard to skin burns are
normally lower than for burns to the respiratory tract. However, thermal burns to the respiratory tract can occur upon
inhalation of air above 60 °C when saturated with water vapour.
4.2 Radiation
−2
The tenability limit for exposure of skin to radiant heat is approximately 2,5 kW·m . Below this incident heat
flux level, exposure can be tolerated for 30 min or longer without significantly affecting tenability. Above this
threshold value, the time, t , expressed in minutes, to second degree burning of skin due to radiant heat
Irad
decreases rapidly according to Error! Reference source not found.Error! Reference source not
[1]
found.Formula (1) .].
−1,56
𝑡 = 6,9𝑞
Irad
(1)
where q is the radiant heat flux, expressed in kilowatts per square metre.
As with toxic gases, an exposed occupant may be considered to accumulate a dose of radiant heat over a period
of time. The FED (Fractionalfractional effective dose) of radiant heat accumulated per minute is the reciprocal
of t .
Irad
NOTE Radiant heat tends to be directional, producing localized heating of particular areas of skin even though the
air temperature in contact with other parts of the body can be relatively low. Skin temperature depends upon the balance
between the rate of heat applied to the skin surface and the removal of heat subcutaneously by the blood. Thus, there is
a threshold radiant flux below which significant heating of the skin is prevented but above which quite rapid heating
occurs.
The time to experiencing pain due to radiant heat can have a behavioural effect on the time to compromised
tenability. The time, t , expressed in minutes, to experiencing pain due to radiant heat is a somewhat more
Irad
strongly inverse function of radiant heat than that for the burning of skin. It is expressed by Error! Reference
[1]
source not found.Error! Reference source not found.Formula (2) .].
−1,9
𝑡 = 4,2𝑞
Irad
(2)
where q is the radiant heat flux, expressed in kilowatts per square metre.
Based on the above information, it is estimated that the uncertainty associated with the use of Error!
Reference source not found.Formulae (1) and Error! Reference source not found.(2) is ±25 %.
−2
Moreover, an irradiance of 2,5 kW·m would correspond to a source surface temperature of approximately
200 °C, which is most likely to be exceeded near the fire, where conditions are changing rapidly.
© ISO #### 2026 – All rights reserved
ISO/DIS FDIS 13571-5:20252026(en)
4.3 Convection
4.3.1 4.3.1 Calculation of the time to prevention of escape under conditions of exposure to convective heat
from air containing less than 10 % by volume of water vapour can be made using either Error! Reference
[52] [63]
source not found.[5] or Error! Reference source not found.[6]Formula (3) or Formula (4) .
As with toxic gases, an exposed occupant can be considered to accumulate a dose of convected heat over a
period of time. The FED of convected heat accumulated per minute is the reciprocal of t .
Iconv
4.3.2 4.3.2 The time, t , expressed in minutes, to experiencing pain due to convective heat accumulated
Iconv
per minute depends upon the extent to which an exposed occupant is clothed and the nature of the clothing.
[Error! Reference source
For fully clothed subjects, Error! Reference source not found.Formula (3) is appropriate
not found.[4] ]
: :
(3)
−3,61
𝑡 = (4,1  ×  10 ) 𝑇
Iconv
(3)
where T is the temperature, expressed in degrees Celsius.
4.3.3 4.3.3 For unclothed or lightly clothed subjects, it is more appropriate to use Error! Reference
[3] ]
source not found.Error! Reference source not found.Formula (4) . .
7 −3,4
𝑡 = (5  ×  10 ) 𝑇
Iconv
(4)
where the variables are the same as for Error! Reference source not found.Formula (3).
Error! Reference source not found.Formulae (3) and Error! Reference source not found.(4) are empirical fits
to human data. It is estimated that the uncertainty is ±25 %.
NOTE Thermal tolerance data for unprotected skin of humans suggest a limit of about 120 °C for convected heat,
[3]
above which there is, within minutes, the onset of considerable pain along with the production of burns[6]. . Depending
upon the length of exposure, convective heat below this temperature can also cause hyperthermia.
4.4 Radiation and convection cumulative consequences
The body of an exposed occupant may be regarded as acquiring a “dose” of heat over a period of time. A short
exposure to a high radiant-heat flux or temperature is generally less tolerable than a longer exposure to a
lower temperature or heat flux. A methodology based on additive FEDs similar to that used with toxic gases
may be applied and, providing that the temperature experienced by the occupant is stable or increasing, the
total fractional effective dose of heat acquired during an exposure can be calculated using Error! Reference
source not found.Formula (5)::
(5)
𝑡
𝑋 = ∑ ( 1 ⁄𝑡 + 1 ⁄𝑡 ) 𝛥𝑡
FED Irad Iconv
𝑡
(5)
−2
In areas within an occupancy where the radiant flux to the skin is under 2,5 kW·m , the term (1/t ) in Error!
Irad
Reference source not found.Formula (5) is set at zero.
ISO #####-#:####(X/FDIS 13571-5:2026(en)
The uncertainty associated with the use of Error! Reference source not found.Formula (5) is dependent
upon the uncertainties with the use of Error! Reference source not found., Error! Reference source not
found.Formulae (1), (2), (3), Error! Reference source not found. and Error! Reference source not found.(4).
4.5 Tenability limit
In the same manner as with toxic-gas exposures, the time at which the FED accumulated sum exceeds a
specified threshold value represents the time to compromised tenability relative to chosen safety criteria; see
ISO 13571-1 and ISO 13571-3.
5 Smoke-obscuration model
The principle of the smoke-obscuration model is based on the concept of minimum detect
...

PROJET FINAL
Norme
internationale
ISO/TC 92/SC 3
Composants dangereux du feu —
Secrétariat: AFNOR
Partie 5:
Début de vote:
2026-08-21
Modèles de chaleur,
d'obscurcissement dû à la fumée et
Vote clos le:
2026-10-16
de perte de masse
Life-threatening components of fire —
Part 5: Heat, smoke obscuration and mass loss models
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PROJET FINAL
Norme
internationale
ISO/TC 92/SC 3
Composants dangereux du feu —
Secrétariat: AFNOR
Partie 5:
Début de vote:
Modèles de chaleur, 2026-08-21
d'obscurcissement dû à la fumée et
Vote clos le:
2026-10-16
de perte de masse
Life-threatening components of fire —
Part 5: Heat, smoke obscuration and mass loss models
LES DESTINATAIRES DU PRÉSENT PROJET SONT
INVITÉS À PRÉSENTER, AVEC LEURS OBSERVATIONS,
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Tous droits réservés. Sauf prescription différente ou nécessité dans le contexte de sa mise en œuvre, aucune partie de cette
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Publié en Suisse Numéro de référence
ii
Sommaire Page
Avant-propos .iv
Introduction .v
1 Domaine d'application . 1
2 Références normatives . 1
3 Termes et définitions . 1
4 Chaleur . 2
4.1 Voies d'exposition à la chaleur .2
4.2 Rayonnement .2
4.3 Convection .3
4.4 Conséquences cumulées du rayonnement et de la convection .3
4.5 Limite de tenabilité .4
5 Modèle d'obscurcissement par la fumée . 4
6 Modèle de perte de masse pour l'évaluation de la toxicité des gaz de combustion . 5
Bibliographie . 8

iii
Avant-propos
L’ISO (Organisation internationale de normalisation) est une fédération mondiale d’organismes nationaux
de normalisation (comités membres de l’ISO). L’élaboration des Normes internationales est en général
confiée aux comités techniques de l’ISO. Chaque comité membre intéressé par une étude a le droit de faire
partie du comité technique créé à cet effet. Les organisations internationales, gouvernementales et non
gouvernementales, en liaison avec l’ISO participent également aux travaux. L’ISO collabore étroitement avec
la Commission électrotechnique internationale (IEC) en ce qui concerne la normalisation électrotechnique.
Les procédures utilisées pour élaborer le présent document et celles destinées à sa mise à jour sont
décrites dans les Directives ISO/IEC, Partie 1. Il convient, en particulier, de prendre note des différents
critères d'approbation requis pour les différents types de documents ISO. Le présent document
a été rédigé conformément aux règles de rédaction données dans les Directives ISO/IEC, Partie 2
(voir www.iso.org/directives).
L'ISO attire l'attention sur le fait que la mise en application du présent document peut entraîner l'utilisation
d'un ou de plusieurs brevets. L'ISO ne prend pas position quant à la preuve, à la validité et à l'applicabilité
de tout droit de propriété revendiqué à cet égard. À la date de publication du présent document, l'ISO
n'avait pas reçu notification qu'un ou plusieurs brevets pouvaient être nécessaires à sa mise en application.
Toutefois, il y a lieu d'avertir les responsables de la mise en application du présent document que des
informations plus récentes sont susceptibles de figurer dans la base de données de brevets, disponible à
l'adresse www.iso.org/brevets. L'ISO ne saurait être tenue pour responsable de ne pas avoir identifié tout ou
partie de tels droits de brevet.
Les appellations commerciales éventuellement mentionnées dans le présent document sont données pour
information, par souci de commodité, à l’intention des utilisateurs et ne sauraient constituer un engagement.
Pour une explication de la nature volontaire des normes, la signification des termes et expressions
spécifiques de l'ISO liés à l'évaluation de la conformité, ou pour toute information au sujet de l'adhésion de
l'ISO aux principes de l'Organisation mondiale du commerce (OMC) concernant les obstacles techniques au
commerce (OTC), voir www.iso.org/iso/fr/avant-propos.html.
Le présent document a été élaboré par le comité technique ISO/TC 92, Sécurité au feu, sous-comité 3, Dangers
pour les personnes et l'environnement dus au feu.
Une liste de toutes les parties de la série ISO 13571 se trouve sur le site web de l'ISO.
Il convient que l'utilisateur adresse tout retour d'information ou toute question concernant le présent
document à l'organisme national de normalisation de son pays. Une liste exhaustive desdits organismes se
trouve à l'adresse www.iso.org/fr/members.html.

iv
Introduction
La série ISO 13571 est un ensemble de Normes internationales élaborées pour estimer le temps avant que
la tenabilité ne soit compromise et la capacité d'évacuation des occupants lorsqu'ils sont exposés à un
environnement d'incendie. Différentes menaces sont évaluées séparément relatives à l'exposition aux agents
toxiques aigus, à la chaleur et à la fumée. Les interactions potentielles entre les différentes menaces n'ont
pas été traitées dans la série ISO 13571.
Par conséquent, le temps disponible avant que les conditions de tenabilité ne soient compromises est pris
comme étant le plus court des temps disponibles avant que les conditions de tenabilité ne soient compromises
déterminés pour chacune des différentes menaces.
Ces recommandations peuvent également être appliquées à l'estimation du délai de sauvetage des personnes
immobilisées en raison d'une blessure, d'un problème de santé, etc. Le présent document établit des
procédures pour évaluer les composants dangereux du feu de l'analyse du danger d'incendie en termes d'état
des sujets humains exposés à des intervalles de temps discrets. Il permet d'estimer l'effet de conditions de
tenabilité au-delà duquel il est estimé que les occupants ne sont plus en mesure de prendre des mesures
efficaces pour réaliser leur propre évacuation. Il permet d'estimer l'effet de conditions de tenabilité pour
chacun des composants des effluents du feu, l'effet le plus important étant celui qui se manifeste en premier.
Bien que l'incapacité des occupants à réaliser leur propre évacuation soit cohérente avec la définition de
l'incapacitation (voir l'ISO 13943), ce terme n'est pas utilisé dans le présent document en raison de son
interprétation potentiellement large permettant d'inclure de nombreux effets, y compris un collapsus
cardiovasculaire et une perte de connaissance, qui ne sont pas traités. Le présent document se concentre
spécifiquement sur la prise de mesures efficaces pour réaliser l'évacuation, car elle peut être influencée par
les réponses physiologiques et comportementales engendrées par une exposition aux composants dangereux
du feu.
Les composants dangereux traités dans le présent document comprennent la chaleur et l'obscurcissement
dû à la fumée ainsi qu'un modèle simplifié fondé sur la perte de masse pour l'évaluation de la toxicité des
combustibles.
Les effets chroniques sur la santé et les impacts environnementaux ne sont pas couverts par la
série ISO 13571.
v
PROJET FINAL Norme internationale ISO/FDIS 13571-5:2026(fr)
Composants dangereux du feu —
Partie 5:
Modèles de chaleur, d'obscurcissement dû à la fumée et de
perte de masse
1 Domaine d'application
Le présent document ne constitue que l'un des nombreux outils pouvant être utilisés en ingénierie de la
sécurité incendie. Il est destiné à être utilisé conjointement à des modèles pour l'analyse du déclenchement
et du développement du feu, de la propagation du feu, de la formation et du déplacement des fumées, de
la génération, du transport et de la décroissance des espèces chimiques, et du déplacement des personnes,
ainsi que pour la détection et la suppression de l'incendie. Le présent document ne doit être utilisée que dans
ce contexte.
Le présent document traite des conséquences de l'exposition d'êtres humains à la chaleur, de l'obscurcissement
induit par la fumée et propose un modèle de toxicité simplifié fondé sur la perte de masse. L'environnement
thermique d'un feu en fonction du temps et les concentrations d'aérosol sont déterminés par le taux de
croissance du feu et le schéma de ventilation. Une fois ces paramètres déterminés, la méthodologie présentée
dans le présent document peut être utilisée pour estimer le temps avant que les individus ne puissent plus
réaliser leur propre évacuation ou atteindre un lieu de refuge sûr.
2 Références normatives
Les documents suivants sont cités dans le texte de sorte qu’ils constituent, pour tout ou partie de leur
contenu, des exigences du présent document. Pour les références datées, seule l’édition citée s’applique. Pour
les références non datées, la dernière édition du document de référence s'applique (y compris les éventuels
amendements).
ISO 13943, Sécurité au feu — Vocabulaire
ISO 13571-1, Composants dangereux du feu — Partie 1: Lignes directrices pour l’estimation du temps disponible
avant que les conditions de tenabilité ne soient compromises — Méthode A
ISO 13571-3, Composants dangereux du feu — Partie 3: Lignes directrices pour l’estimation du temps disponible
avant que les conditions de tenabilité ne soient compromises — Méthode B
3 Termes et définitions
Pour les besoins du présent document, les termes et les définitions de l'ISO 13943, ISO 13571-1 et
de l'ISO 13571-3 s'appliquent.
L'ISO et l'IEC tiennent à jour des bases de données terminologiques destinées à être utilisées en normalisation,
consultables aux adresses suivantes:
— ISO Online browsing platform: disponible à l'adresse https:// www .iso .org/ obp
— IEC Electropedia: disponible à l'adresse https:// www .electropedia .org/

4 Chaleur
4.1 Voies d'exposition à la chaleur
Il existe trois mécanismes fondamentaux par lesquels une exposition à la chaleur peut constituer un danger
de mort:
a) Hyperthermie;
b) brûlures de la surface du corps;
c) brûlures des voies respiratoires.
Pour une utilisation dans la modélisation du danger de mort dû à l'exposition à la chaleur dans des incendies,
il est nécessaire de ne tenir compte que de deux critères:
— le seuil de brûlure au deuxième degré de la peau;
— l'exposition lorsque l'hyperthermie est suffisante pour provoquer une détérioration mentale et donc une
menace pour la survie.
NOTE Les brûlures thermiques des voies respiratoires par inhalation d'air contenant moins de 10 % en volume
de vapeur d'eau ne se produisent pas en l'absence de brûlures de la peau ou du visage; par conséquent, les limites de
tenabilité en ce qui concerne les brûlures de la peau sont normalement plus faibles que pour les brûlures des voies
respiratoires. Toutefois, des brûlures thermiques des voies respiratoires peuvent se produire en cas d'inhalation d'air
à plus de 60 °C saturé en vapeur d'eau.
4.2 Rayonnement
−2
La limite de tenabilité pour l'exposition de la peau à la chaleur radiante est approximativement de 2,5 kW·m .
Au-dessous de ce niveau de flux de chaleur incident, l'exposition peut être tolérée pendant 30 min ou plus
sans affecter de manière significative la tenabilité. Au-dessus de ce seuil, le délai, t , exprimé en minutes,
Irad
avant qu'il se produise une brûlure de la peau au deuxième degré due à la chaleur radiante diminue
[4]
rapidement conformément à la Formule (1) .
15, 6
tq69, (1)
Irad
où q est le flux de chaleur radiante, exprimé en kilowatts par mètre carré.
Comme pour les gaz toxiques, il peut être considéré qu'un occupant exposé accumule une dose de chaleur
radiante sur une période. La FED (dose effective fractionnelle) de chaleur radiante accumulée par minute est
la réciproque de t .
Irad
NOTE La chaleur radiante a tendance à être directionnelle, produisant un échauffement localisé de zones
particulières de la peau même si la température de l'air en contact avec les autres parties du corps peut être
relativement faible. La température de la peau dépend de l'équilibre entre le débit thermique appliqué à la surface de
la peau et l'extraction sous-cutanée de chaleur par le sang. Par conséquent, il existe un flux énergétique au-dessous
duquel un échauffement significatif de la peau est évité, mais au-dessus duquel un échauffement assez rapide se
produit.
Le délai avant de ressentir une douleur due à la chaleur radiante peut avoir un effet comportemental sur le
temps disponible avant que les conditions de tenabilité ne soient compromises. Le délai, t , exprimé en
Irad
minutes, avant de ressentir une douleur due à la chaleur radiante est une fonction inverse relativement plus
[4]
marquée de la chaleur radiante que pour la brûlure de la peau. Il est formulé par la Formule (2) .
19,
tq42, (2)
Irad
où q est le flux de chaleur radiante, exprimé en kilowatts par mètre carré.

Sur la base des informations précédentes, il est estimé que l'incertitude associée à l'utilisation de
−2
la Formule (1) et de la Formule (2) est de ±25 %. De plus, un rayonnement de 2,5 kW·m correspondrait à
une température de surface de la source d'environ 200 °C, valeur très probablement dépassée à proximité
du feu où les conditions évoluent rapidement.
4.3 Convection
4.3.1 Le temps disponible pour l'évacuation dans des conditions d'exposition à la chaleur transmise par
convection par l'air contenant moins de 10 % en volume de vapeur d'eau peut être calculé en utilisant soit la
[5] [6]
Formule (3) soit la Formule (4) .
Comme pour les gaz toxiques, il peut être considéré qu'un occupant exposé accumule une dose de chaleur
transmise par convection sur une période. La FED de chaleur par convection accumulée par minute est la
réciproque de t .
Iconv
4.3.2 Le délai, t , exprimé en minutes, avant de ressentir une douleur due à la chaleur de convection
Iconv
accumulée par minute dépend de l'étendue de la protection par des vêtements de l'occupant exposé et
de la nature des vêtements. Pour des sujets entièrement protégés par des vêtements, la Formule (3) est
[7]
appropriée :
83 ,61
tT(,41 10 ) (3)
Iconv
où T est la température, exprimée en degrés Celsius.
[6]
4.3.3 Pour des sujets dévêtus ou légèrement vêtus, il est plus approprié d'utiliser la Formule (4) .
73 ,4
tT()510 (4)
Iconv
où les variables sont identiques à celles de la Formule (3).
La Formule (3) et la Form
...