oSIST prEN ISO 13943:2026

• Abstract:

  This document defines terminology relating to fire safety as used in ISO and IEC International Standards.

• Status: Not Published
• Public Enquiry End Date: 30-Dec-2026
• ICS: 01.040.13 - Environment. Health protection. Safety (Vocabularies)
• ICS: 13.220.01 - Protection against fire in general
• Technical Committee: POZ - Požarna varnost
• Current Stage: 4020 - Public enquire (PE) (Adopted Project)
• Start Date: 02-Nov-2026
• Due Date: 22-Mar-2027
• Ref Project: prEN ISO 13943 - Fire safety - Vocabulary (ISO/DIS 13943:2026)

• Revises: SIST EN ISO 13943:2024 - Fire safety - Vocabulary (ISO 13943:2023)
• Effective Date: 15-Nov-2023

SLOVENSKI STANDARD
01-december-2026
Požarna varnost - Slovar (ISO/DIS 13943:2026)
Fire safety - Vocabulary (ISO/DIS 13943:2026)
Brandschutz - Vokabular (ISO/DIS 13943:2026)
Sécurité au feu - Vocabulaire (ISO/DIS 13943:2026)
Ta slovenski standard je istoveten z: prEN ISO 13943
ICS:
01.040.13 Okolje. Varovanje zdravja. Environment. Health
Varnost (Slovarji) protection. Safety
(Vocabularies)
13.220.01 Varstvo pred požarom na Protection against fire in
splošno general
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

DRAFT
International
Standard
ISO/DIS 13943
ISO/TC 92
Fire safety — Vocabulary
Secretariat: BSI
Sécurité au feu — Vocabulaire
Voting begins on:
2026-10-05
ICS: 13.220.01; 01.040.13
Voting terminates on:
2026-12-28
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Reference number
ISO/DIS 13943:2026(en)
DRAFT
ISO/DIS 13943:2026(en)
International
Standard
ISO/DIS 13943
ISO/TC 92
Fire safety — Vocabulary
Secretariat: BSI
Sécurité au feu — Vocabulaire
Voting begins on:
ICS: 13.220.01; 01.040.13
Voting terminates on:
THIS DOCUMENT IS A DRAFT CIRCULATED
FOR COMMENTS AND APPROVAL. IT
IS THEREFORE SUBJECT TO CHANGE
AND MAY NOT BE REFERRED TO AS AN
INTERNATIONAL STANDARD UNTIL
PUBLISHED AS SUCH.
This document has not been edited by the ISO Central Secretariat.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL,
© ISO 2026
TECHNOLOGICAL, COMMERCIAL AND
USER PURPOSES, DRAFT INTERNATIONAL
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Published in Switzerland Reference number
ISO/DIS 13943:2026(en)
ii
ISO/DIS 13943:2026(en)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
Bibliography .64
Index .66

iii
ISO/DIS 13943:2026(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 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 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, in collaboration with the
European Committee for Standardization (CEN) Technical Committee CEN/TC 127, Fire safety in buildings, in
accordance with the Agreement on technical cooperation between ISO and CEN (Vienna Agreement).
This fifth edition cancels and replaces the fourth edition (ISO 13943:2023), which has been technically
revised.
The main changes compared to the previous edition are as follows:
— 55 terms have been added, and several term definitions have been revised.
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
ISO/DIS 13943:2026(en)
Introduction
0.1  General
Over the last two decades, there has been a significant growth in the field of fire safety. There has been a
considerable development of fire safety engineering design, especially as it relates to construction projects,
as well as the development of concepts related to performance-based design. With this continuing evolution,
there is an increasing need for agreement on a common language in the broad and expanding area of fire
safety, beyond what has traditionally been limited to the field of fire testing.
The first edition of this document, ISO 13943:2000, contained definitions of about 180 terms. However, the
areas of technology that are related to fire safety have continued to evolve rapidly and this edition contains
many new terms and their definitions, as well as revised definitions of some of the terms that were in earlier
editions.
This document defines general terms in order to establish a vocabulary applicable to fire safety, including
fire safety in buildings and civil engineering works and other elements within the built environment. It
will be updated as terms and definitions for further concepts in the field of fire safety are agreed upon and
developed.
It is important to note that it is possible that some fire safety terms may have a somewhat different
interpretation than the one used in this document when used for regulations. In that case, the definition
given in this document may not apply.
The terms in this document concern:
— fundamental concepts;
— more specific concepts, such as those used specifically in fire testing or in fire safety engineering and
potentially in ISO or IEC International Standards relating to fire; and
— related concepts, such as terms used in building and civil engineering.
The layout is designed according to ISO 10241-1:2011. The terms are presented in English alphabetical order,
and preferred terms are written in bold type, with admitted and deprecated terms listed below in normal
type.
0.2  Use of the term “item”
For the purposes of this document, the term “item” (in French “objet”) is used to represent any single object
or assembly of objects. It may cover, for example, material, product, assembly, structure or building, as
required in the context of any individual definition.
If the “item” under consideration is a test specimen, then the term “test specimen” is used.

v
DRAFT International Standard ISO/DIS 13943:2026(en)
Fire safety — Vocabulary
1 Scope
This document defines terminology relating to fire safety as used in ISO and IEC International Standards.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological 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/
3.1
abnormal heat
heat that is additional to that resulting from use under normal conditions, up to and
including that which causes a fire (3.146, 3.147, 3.148, 3.138)
3.2
absorptivity
ratio of the absorbed radiant heat flux (3.358) to the incident radiative heat flux (3.361)
Note 1 to entry: The absorptivity is dimensionless.
3.3
acceptance criteria
criteria that form the basis for assessing the acceptability of the safety of a design of a built environment
(3.36)
Note 1 to entry: The criteria can be qualitative, quantitative or a combination of both.
3.4
accuracy
closeness of the agreement between the result of a measurement and the true value of the measurand
[SOURCE: ASTM E176-2024]
3.5
activation time
time interval from response by a sensing device until the suppression system (3.418), smoke (3.389) control
system, alarm system or other fire safety system is fully operational

ISO/DIS 13943:2026(en)
3.6
active fire protection
method(s) used to reduce or prevent the spread and effects of fire (3.146, 3.147, 3.148), heat or smoke (3.389)
by virtue of detection and/or suppression of the fire and which require a certain amount of motion and/or
response to be activated
EXAMPLE The application of agents (e.g. halon gas or water spray) to the fire (3.146) or the control of ventilation
and/or smoke.
Note 1 to entry: Compare with the terms passive fire protection (3.328) and suppression systems (3.418).
3.7
actual delivered density
ADD
rate at which water is deposited from an operating sprinkler onto the top horizontal surface of a simulated
burning combustible array
Note 1 to entry: ADD is typically determined relative to a specific heat release rate (3.245) of a fire (3.146).
−1
Note 2 to entry: The typical unit is mm⋅min .
[SOURCE: ISO 6182-1:2021; 4.1.1]
3.8
acute effect
sharp or severe effect
Note 1 to entry: Compare with the term chronic effect (3.57).
Note 2 to entry: Generally used in reference to human health effects.
3.9
acute toxicity
toxicity (3.450) that causes rapidly occurring toxic (3.458) effects
Note 1 to entry: Compare with the term toxic potency (3.447).
3.10
aerosol
suspension of droplets (3.94) and/or solid particles in a gas phase which are generated by fire (3.146)
Note 1 to entry: The size of the droplets or particles typically ranges from under 10 nm to over 10 μm.
Note 2 to entry: Compare with the term droplets.
3.11
aerosol particles
individual piece of solid material that is part of the dispersed phase in an aerosol (3.10)
Note 1 to entry: There are two categories of fire (3.146) aerosol particles: unburned or partially burned particles
containing a high proportion of carbon (i.e. “soot”; 3.397), and relatively completely combusted, small particle
sized “ashes” (3.24). Soot particles of small diameter, (i.e. about 1 μm), typically consist of small elementary spheres
of between 10 nm and 50 nm in diameter. Formation of soot particles is dependent on many parameters including
nucleation, agglomeration and surface growth. Oxidation (3.324) of soot particles, i.e. further combustion (3.62), is
also possible.
3.12
afterflame
flame (3.186) that persists after the ignition source (3.244) has been removed

ISO/DIS 13943:2026(en)
3.13
afterflame time
length of time for which an afterflame (3.12) persists under specified conditions
Note 1 to entry: Compare with the term duration of flaming (3.95).
3.14
afterglow
persistence of glowing combustion (3.221) after both removal of the ignition source (3.244) and the
cessation of any flaming combustion (3.197)
3.15
afterglow time
length of time for which an afterglow (3.14) persists under specified conditions
3.16
agent-based model
computational model for simulating the actions and interactions of autonomous agents using a set of rules
[SOURCE: ISO 20414:2020, 3.4]
3.17
agent outlet
orifice of a piping system by means of which an extinguishing fluid can be applied towards the source of a
fire (3.146)
3.18
alarm time
time interval between ignition (3.242) of a fire (3.148) and activation of an alarm
Note 1 to entry: The time of ignition can be known, for example, in the case of a fire model (3.160) or a fire test (3.192),
or it can be assumed, for example, it can be based on an estimate working back from the time of detection. The basis on
which the time of ignition is determined is always stated when the alarm time is specified.
3.19
alight
lit, adj. CA, US
lighted
undergoing combustion (3.62)
3.20
analyte
substance that is identified or quantified in a specimen (3.400) during an analysis
3.21
arc resistance
ability of an electrically insulating material to resist the influence of an electric arc,
under specified conditions
Note 1 to entry: The arc resistance is identified by the length of the arc, the absence or presence of a conducting path,
and the burning or damage of the test specimen (3.444).
3.22
area burning rate
DEPRECATED: burning rate
DEPRECATED: rate of burning
area of material burned (3.38) per unit time under specified conditions
2 −1
Note 1 to entry: The typical unit is m ⋅s .

ISO/DIS 13943:2026(en)
3.23
arson
crime of setting a fire (3.148), usually with intent to cause damage
3.24
ash
ashes
mineral residue resulting from complete combustion (3.66)
3.25
asphyxiant
toxicant (3.449) that causes hypoxia, which can result in central nervous system depression or cardiovascular
effects
3.26
atmospheric transmissivity
ratio of the transmitted radiation (3.359) intensity after passing through unit length of a participating
medium (carbon dioxide, water vapour, dust and fog) to the radiation intensity that would have passed the
same distance through clean air
[SOURCE: ISO 24678-7:2019, 3.8]
3.27
attended control room
control room (attended) (3.74)
3.28
auto-ignition
spontaneous ignition
self-ignition
unpiloted ignition
DEPRECATED: spontaneous combustion
ignition (3.242) caused by an internal exothermic reaction
Note 1 to entry: The ignition can be caused either by self-heating (3.383) or, in the case of unpiloted ignition, by heating
from an external source, as long as the external source does not include an open flame (3.186).
Note 2 to entry: In North America, “spontaneous ignition” is the preferred term used to designate ignition caused by
self-heating.
Note 3 to entry: Compare with the terms piloted ignition (3.334) and spontaneous ignition temperature (3.406).
3.29
auto-ignition temperature
DEPRECATED: self-ignition temperature
minimum temperature at which auto-ignition (3.28) is obtained in a fire test (3.192)
Note 1 to entry: The typical unit is °C.
Note 2 to entry: Compare with the term spontaneous ignition temperature (3.406).
3.30
available safe escape time
ASET
time available for escape
calculated time interval between the time of ignition (3.242) and the time at which conditions become
such that the occupant (3.321) is estimated to be incapacitated, i.e. unable to take effective action to escape
(3.114) to a safe refuge (3.376) or place of safety (3.335)
Note 1 to entry: The time of ignition can be known, for example, in the case of a fire model (3.160) or a fire test (3.192),
or it can be assumed, for example, it can be based on an estimate working back from the time of detection. The basis on
which the time of ignition is determined needs to be stated.

ISO/DIS 13943:2026(en)
Note 2 to entry: This definition equates incapacitation (3.250) with failure to escape. Other criteria for ASET are
possible. If an alternate criterion is selected, it needs to be stated.
Note 3 to entry: Each occupant may have a different value of ASET, depending on that occupant’s personal
characteristics.
3.31
backdraft
rapid flaming combustion (3.197) caused by the sudden introduction of air into a confined oxygen-deficient
space that contains hot products of incomplete combustion (3.62)
Note 1 to entry: In some cases, these conditions may result in an explosion (3.122).
3.32
behavioural scenario
description of the behaviour of occupants (3.321) during the course of a fire (3.148)
3.33
behavioural uncertainty
uncertainty (3.459) in evacuation (3.115) scenarios associated with the impact of human behaviour in fire
(3.235) during evacuation
[SOURCE: ISO 20414:2020, 3.7]
3.34
black body
form that completely absorbs any electromagnetic radiation (3.359) falling upon it
3.35
black body radiation source
ideal thermal radiation (3.437) source which completely absorbs all incident heat radiation (3.359), whatever
wavelength and direction
Note 1 to entry: The emissivity (3.103) of a black body radiation source is unity.
Note 2 to entry: A black body (3.34) can also be an ideal radiator of energy.
[SOURCE: ISO 14934-1:2010, 3.1.7, modified — original Notes 1 and 2 to entry have been removed. New
Notes 1 and 2 to entry have been added.]
3.36
building element
integral part of a built environment (3.37)
Note 1 to entry: This includes floors, walls, beams, columns, doors and penetrations, but does not include contents.
Note 2 to entry: This definition is wider in its scope than that given in ISO 6707-1.
3.37
built environment
building or other structure
EXAMPLE Off-shore platforms, civil engineering works such as tunnels, bridges and mines, and means of
transportation such as motor vehicles and marine vessels.
Note 1 to entry: ISO 6707-1 contains a number of terms and definitions for concepts related to the built environment.
3.38
buoyant plume
convective updraft of fluid above a heat source
Note 1 to entry: Compare with the term fire plume (3.162).

ISO/DIS 13943:2026(en)
3.39
burn, intransitive verb
undergo combustion (3.62)
3.40
burn, transitive verb
cause combustion (3.62)
3.41
burned area
that part of the damaged area (3.79) of a material that has been destroyed by combustion (3.62) or pyrolysis
(3.355), under specified conditions
Note 1 to entry: The typical unit is m2.
3.42
burned length
maximum extent in a specified direction of the burned area (3.41)
Note 1 to entry: The typical unit is m.
Note 2 to entry: Compare with the term damaged length (3.80).
3.43
burning behaviour
response of a test specimen (3.444), when it burns (3.38) under specified conditions, to examination of
reaction to fire (3.364) or fire resistance (3.165)
Note 1 to entry: In the US the burning behaviour in a fire test (3.192) is designated as fire-test-response characteristic
while the burning behaviour in an accidental fire (3.148) is designated as fire performance.
3.44
burning debris
burning material which has detached from a burning item or test specimen (3.444) during a fire (3.146, 3.147,
3.148) or fire test (3.192) and continues to burn (3.39) on the floor
Note 1 to entry: See flaming debris (3.212).
Note 2 to entry: Compare with the terms dropping droplet (3.45), flaming debris (3.212) and flaming droplet (3.213).
3.45
dropping droplet
flaming (3.210) molten or flaming liquefied drop which falls from a test specimen (3.444) during a fire test
(3.192) and continues to burn (3.39) on the floor
Note 1 to entry: See flaming droplet (3.213).
Note 2 to entry: Compare with the terms flaming debris (3.212) and burning debris (3.44).
3.46
bursting
violent rupture of an object due to an overpressure within it or upon it
3.47
bushfire
unplanned fire (3.148) in a vegetated area
Note 1 to entry: This term is used primarily, but not exclusively, in Australia, New Zealand, and Africa.
[SOURCE: ISO/TR 24188:2022, 3.1.1, modified — "as opposed to an urban area" and Notes 2 and 3 to entry
have been removed.]
ISO/DIS 13943:2026(en)
3.48
calibration
process of adjusting modelling parameters in a computational fire model (3.160) for the
purpose of improving agreement with experimental data
3.49
calibration related to fire modelling
process of adjusting modelling parameters in a computational model for the purpose of improving agreement
with experimental data
3.50
calorimeter
apparatus that measures heat
Note 1 to entry: Compare with the terms heat release rate calorimeter (3.231) and mass calorimeter (3.286).
3.51
carboxyhaemoglobin
compound formed when CO combines with haemoglobin
Note 1 to entry: Haemoglobin has an affinity for binding to CO that is approximately 245 times higher than that
for binding to oxygen. Therefore, the ability of haemoglobin to carry oxygen is seriously compromised during CO
poisoning.
3.52
carboxyhaemoglobin saturation
percentage of blood haemoglobin converted to carboxyhaemoglobin (3.51) from the reversible reaction with
inhaled carbon monoxide
3.53
ceiling jet
gas motion in a hot gas layer near a ceiling that is generated by the buoyancy of a fire plume (3.162) that is
impinging upon the ceiling
3.54
char, noun
carbonaceous residue resulting from pyrolysis (3.355) or incomplete combustion (3.62)
3.55
char, verb
form char (3.54)
3.56
char length
length of charred area
Note 1 to entry: Compare with the terms burned length (3.41) and damaged length (3.80).
Note 2 to entry: In some standards, char length is defined by a specific test method.
3.57
chimney effect
upward movement of hot fire effluent (3.158) caused by convection (3.76) currents confined within an
essentially vertical enclosure (3.112)
Note 1 to entry: This usually draws more air into the fire (3.146).
3.58
chronic effect
continuing over a long time period or recurring at low levels frequently
Note 1 to entry: Compare with the term acute effect (3.8).

ISO/DIS 13943:2026(en)
Note 2 to entry: Generally used in reference to human health effects.
3.59
clinker
solid agglomerate of residues formed by either complete combustion (3.66) or incomplete combustion (3.62)
and which can result from complete or partial melting
3.60
combustible
capable of being ignited (3.241) and burned (3.38)
3.61
combustible, noun
item capable of combustion (3.62)
3.62
combustible load
theoretical mass that would be lost from a test specimen (3.444) when it is assumed to have undergone
complete combustion (3.66) in a fire test (3.192)
3.63
combustion
exothermic reaction of a substance with an oxidizing agent (3.325)
Note 1 to entry: Combustion generally emits fire effluent (3.158) accompanied by flames (3.198) and/or glowing
(3.235).
3.64
combustion efficiency
ratio of the amount of heat release (3.234) in incomplete combustion (3.63) to the theoretical heat of complete
combustion (3.67)
Note 1 to entry: Combustion efficiency can be calculated only for cases where complete combustion can be defined.
Note 2 to entry: Combustion efficiency is usually expressed as a percentage.
Note 3 to entry: The combustion efficiency is dimensionless.
3.65
combustion product
product of combustion
solid, liquid and gaseous material resulting from combustion (3.63)
Note 1 to entry: Combustion products can include fire effluent (3.158), ash (3.24), char (3.54), clinker (3.59) and/or soot
(3.441).
3.66
common mode failure
failure involving a single source that affects more than one type of safety system simultaneously
3.67
complete combustion
combustion (3.62) in which all the combustion products (3.64) are fully oxidized
Note 1 to entry: This means that, when the oxidizing agent (3.325) is oxygen, all carbon is converted to carbon dioxide,
and all hydrogen is converted to water.
Note 2 to entry: If elements other than carbon, hydrogen and oxygen are present in the combustible (3.61) material,
those elements are converted to the most stable products in their standard states at 298 K.
3.68
composite material
combination of two or more discrete materials

ISO/DIS 13943:2026(en)
3.69
computerized model
operational computer program that implements a conceptual model (3.71)
3.70
concentration
DEPRECATED: ppm
DEPRECATED: ppm by volume
mass of a dispersed or dissolved material in a given volume
−3
Note 1 to entry: For fire effluent (3.158), the typical unit is g⋅m .
Note 2 to entry: For toxic gas (3.494), concentration is usually expressed as a volume fraction (3.473) where T = 298 K
3 3 −6
and P = 1 atm, with typical units of μL/L (= cm /m = 10 ).
Note 3 to entry: The concentration of a gas at a temperature, T, and a pressure, P, can be calculated from its volume
fraction (assuming ideal gas behaviour) by multiplying the volume fraction by the density of the gas at that temperature
and pressure.
Note 4 to entry: Pascal (Pa) is the SI unit for pressure. However, atmosphere (atm) is typically used in this context,
where 1 atm = 101,3 kPa.
Note 5 to entry: The numerical value of a concentration in ppm is identical to that for a concentration in μL/L.
3.71
concentration-time curve
plot of the concentration (3.70) of a toxic gas (3.494) or fire effluent (3.158) as a function of time
−3
Note 1 to entry: For fire effluent, concentration is usually measured in units of g⋅m .
Note 2 to entry: For toxic gas, concentration is usually expressed as a volume fraction (3.473) where T = 298 K and
3 3 −6
P = 1 atm, with typical units of μL/L (= cm /m = 10 ).
Note 3 to entry: Pascal (Pa) is the SI unit for pressure. However, atmosphere (atm) is typically used in this context,
where 1 atm = 101,3 kPa.
3.72
conceptual model
information, mathematical modelling, data, assumptions, boundary conditions and mathematical equations
that describes the (physical) system or process of interest
3.73
construction works
everything that is constructed or results from construction operations
Note 1 to entry: Construction works covers all buildings (ISO 6707-1:2004, 3.1.3) and civil engineering works
(ISO 6707-1:2004, 3.1.2) .
[SOURCE: ISO 6707-1:2014, 3.1.1, modified — Note 1 to entry has been added.]
Note 2 to entry: This can refer to a building, piece of civil infrastructure (road, bridge, pipeline, etc.) or a landscape
element and is extended to include aggregations of those elements to form an urban precinct, campus, or other
institutional facility.
3.74
control room (attended)
room with people who have the duty to control the smoke and heat exhaust ventilation system (3.428)
permanently, monitor the incoming signals from the smoke and heat control system (3.426) and put the
system into operation in case of smoke alarm
Note 1 to entry: This ensures that the smoke and heat control system is running and items such as dampers are in
position within the system response time.

ISO/DIS 13943:2026(en)
[SOURCE: ISO 21927-8:2017, 3.2, modified — definition wording simplified using updated terminology and
the reference to time frame moved to a new Note 2 to entry.]
3.75
controlled burn
operational strategy where the application of firefighting media such as water or foam is restricted or
avoided
Note 1 to entry: Controlled burns are often conducted to minimize damage to public health and the environment.
Other motivations for controlled burn may include limited danger of fire (3.147) spread, concerns about firefighter
safety, or limited capacity and resources at hand for firefighting operations.
Note 2 to entry: The strategy would normally be used to try and prevent water pollution by contaminated firewater.
It can also reduce air pollution due to the better combustion (3.62) and dispersion of pollutants (3.336), but it can
potentially also have adverse impacts, such as allowing or increasing the formation of hazardous and gaseous by-
products. It can also have benefits for firefighter safety and public health.
3.76
convection
transfer of heat by movement of a fluid
3.77
convective heat flux
heat flux (3.240) caused by convection (3.76)
3.78
convective heat transfer
transfer of heat to a surface from a surrounding fluid by convection (3.76)
Note 1 to entry: The amount of heat transfer (3.238) depends on the temperature difference between the fluid and the
surface, the fluid properties, and the fluid velocity and direction.
Note 2 to entry: The fundamental modes of heat transfer are conduction or diffusion, convection (3.76) and radiation
(3.391).
3.79
corrosion damage
physical and/or chemical damage or impaired function caused by chemical action
3.80
corrosion target
sensor used to determine the degree of corrosion damage (3.79), under specified conditions
Note 1 to entry: The sensor may be a product or a component. It may also be a reference material or object used to
simulate the behaviour of a product or a component.
3.81
critical fire load
fire load (3.170) required in a fire compartment (3.154) to produce a fire (3.146, 3.147, 3.148) of sufficient
severity to cause failure of a fire barrier(s) (3.151) or structural member(s) located within or bounding the
fire compartment
3.82
damaged area
total of those surface areas which have been affected permanently by fire (3.147) under specified conditions
Note 1 to entry: Compare with the term burned area (3.40).
Note 2 to entry: Users of this term should specify the types of damage to be considered. This could include, for example,
loss of material, deformation, softening, melting behaviour (3.301), char (3.53) formation, combustion (3.62), pyrolysis
(3.355) or chemical attack.
Note 3 to entry: The typical unit is m .

ISO/DIS 13943:2026(en)
3.83
damaged length
maximum extent in a specified direction of the damaged area (3.79)
Note 1 to entry: Compare with the terms char length (3.55) and burned length (3.41).
3.84
defend in place
life safety strategy in which occupants (3.321) are encouraged to remain in their current location rather
than to attempt escape (3.114) during a fire (3.148)
3.85
deflagration
combustion (3.62) wave propagating at subsonic velocity
Note 1 to entry: If within a gaseous medium, deflagration is the same as a flame (3.186).
3.86
design density
measured volumetric flow rate of water from sprinklers, per unit area, that is delivered in the absence of a
fire (3.148)
−1
Note 1 to entry: The typical unit is mm⋅min .
3.87
design fire
quantitative description of assumed fire (3.146) characteristics within the design fire scenario (3.85)
Note 1 to entry: A design fire is, typically, an idealized description of the variation over time of important fire variables
such as heat release rate (3.245), flame spread rate (3.192), smoke production rate (3.393), toxic gas (3.494) yields
(3.479), and temperature.
3.88
design fire scenario
specific fire scenario (3.176) on which an analysis will be conducted
[SOURCE: ISO/TR 17252:2019, 3.2]
3.89
detection time
time interval between ignition (3.242) of a fire (3.148) and its detection by an automatic or manual system
3.90
deterministic analysis
risk analysis approach in which the fire safety design (3.171) is evaluated using a set of worst credible case
scenarios
[SOURCE: ISO 23932-1:2018, 3.2]
3.91
deterministic model
fire model (3.160) that uses science-based mathematical expressions to produce the same result each time
the method is used with the same set of input data values
3.92
detonation
reaction characterized by a shock wave propagating at a velocity greater than the local speed of sound in the
unreacted material
ISO/DIS 13943:2026(en)
3.93
diffusion flame
flame (3.186) in which combustion (3.62) occurs in a zone where the fuel (3.212) and the oxidizing agent
(3.325) mix, having been initially separate
Note 1 to entry: Compare with the term pre-mixed flame (3.344).
3.94
dioxin
family of halogenated organic compounds, the most common consisting of polychlorinated dibenzofurans
(PCDF) and polychlorinated dibenzodioxins (PCDD), although brominated dioxins and furans are also
important
Note 1 to entry: ISO 16000-14:2009 explains that this term is generally associated with polychlorinated biphenyls
(PCBs), polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs). There are 209
individual PCBs (congeners), 75 PCDDs and 135 PCDFs.
[SOURCE: ISO 26367-2:2017, 3.4, modified — original Notes 1 and 2 to entry have been removed. New Note 1
to entry has been added.]
3.95
direct flame contact
one of the three structure ignition (3.242) pathways, together with firebrands and
radiant heat
Note 1 to entry: Direct flame contact is one of the three structure ignition pathways in a large outdoor fire (3.283),
together with firebrands (3.195) and radiant heat (3.390).
[SOURCE: ISO/TR 24188:2025, 3.1.2, modified]
3.96
doorset
assembly consisting of a fixed part (door frame), one or more movable parts (door leaves), and their door
furniture, the function of which is to allow or to prevent access and egress to a room or a building
Note 1 to entry: A doorset can also include, at floor level, a door saddle (also known as a sill or threshold).
Note 2 to entry: see also fire doorset (3.156) and smoke control doorset (3.428).
Note 3 to entry: A doorset typically also contains smoke seals, such as intumescent seals
[SOURCE: ISO 21542:2021, 3.7]
3.97
draught-free environment
space in which the results of experiments are not significantly affected by the local air speed
Note 1 to entry: A qualitative example is a space in which a wax candle flame (3.186) remains essentially undisturbed.
Quantitative examples are small-scale fire tests (3.388) in which a maximum air speed of 0,1 m⋅s−1 or 0,2 m⋅s−1 is
sometimes specified.
3.98
droplet
aerosol droplet
liquid-phase products, typically generated through pyrolysis (3.355) (reduced oxygen combustion (3.62)
conditions) from both flaming and smouldering (3.394) fires (3.146), which can condense into tarry-like,
spherically-shaped liquid beads
3.99
duration of flaming
length of time for which flaming combustion (3.197) persists under specified conditions
Note 1 to entry: Compare with the term afterflame time (3.13).

ISO/DIS 13943:2026(en)
3.100
ecotoxic
harmful to the environment or a specific ecosystem
[SOURCE: ISO 26367-1:2019, 3.1]
3.101
ecotoxicity
potential for biological, chemical or physical stressors to affect ecosystems
[SOURCE: ISO 26367-1:2019, 3.2]
3.102
effective concentration 50
EC50
concentration (3.69) of a toxic gas (3.494) or fire effluent (3.158), statistically calculated from concentration-
response data, that causes a specified effect in 50 % of a population of a given species within a specified
exposure time (3.125) and post-exposure time (3.339)
Note 1 to entry: Compare with the term IC (3.251).
−3
Note 2 to entry: For fire effluent, the typical unit is g⋅m .
Note 3 to entry: For toxic gas, the typical unit is μL/L (T = 298 K and P = 1 atm); see volume fraction (3.473).
Note 4 to entry: The observed effect is usually a behavioural response, incapacitation (3.250), or death. The EC50 for
incapacitation is termed the IC50. The EC50 for lethality is termed the LC (3.268).
3.103
effective exposure dose 50
Ect50
product of EC50 (3.98) and the exposure time (3.125) over which it was determined
Note 1 to entry: Compare with the term exposure dose (3.124).
−3
Note 2 to entry: For fire effluent (3.158), the typical unit is g⋅min⋅m .
−1
Note 3 to entry: For toxic gas (3.494), the typical unit is μL⋅min⋅L (T = 298 K and P = 1 atm); see volume fraction
(3.473).
Note 4 to entry: Ect50 is a measure of toxic potency (3.447).
3.104
effective heat of combustion
heat released (3.234) from a burning test specimen (3.444) in a given time interval divided by the mass lost
from the test specimen in the same time period
Note 1 to entry: Effective heat of combustion is the same as the net heat of combustion (3.313) if all the test specimen
is converted to volatile combustion products (3.64) and if all the combustion products are fully oxidized.
−1
Note 2 to entry: The typical unit is kJ⋅g .
3.105
elevated temperature
temperature in excess of normal ambient air temperature
3.106
ember
particle of solid material that emits radiant energy, due either to its temperature or to the process of
combustion (3.62) on its surface, and that poses a risk of ignition (3.242) to any materials upon which it is
incident
Note 1 to entry: Compare with the term firebrand (3.195).

ISO/DIS 13943:2026(en)
3.107
emergent behaviour
behaviour which occurs due to the interactions among smaller or simpler entities
which do not exhibit such properties themselves (e.g. agents)
[SOURCE: ISO 20414:2020, 3.17, modified — delimiter "related to evacuation" has been added.]
3.108
emission factor
expression for the ratio of the rate at which a pollutant is emitted as a result of a fire (3.146) to the rate of
that fire.
Note 1 to entry: Commonly expressed in g/kg
Note 2 to entry: Emission factors represent an overall measure of pollutant generation for a given material/ product/
scenario under specific burning conditions. They are the real equivalent to yields (3.534) measured under laboratory
conditions in idealized configurations.
3.109
emissivity
ratio of the radiation (3.359) emitted by a radiant source to the radiation that would be emitted by a black
body radiation source (3.34) at the same temperature
Note 1 to entry: The emissivity is dimensionless.
3.110
empirical formula
chemical formula of a substance in which the relative numbers of atoms of each type are given
Note 1 to entry: Typically, the number for one type of atom is chosen to be an integer (usually C or O). For example, a
particular sample (3.377) might be represented as C ,9O , N C .
6H8 4 1 0,3 l0,01
3.111
enclosed fire
fire (3.146, 3.147, 3.148) which takes place and has been ignited (3.241) inside an enclosure (3.112)
Note 1 to entry: This term is particularly important when defining the ventilation conditions in the fire.
3.112
enclosure
volume defined by bounding surfaces, which may have one or more openings
3.113
enclosure
external casing protecting the electrical and mechanical parts of apparatus
Note 1 to entry: This term excludes cables.
3.114
end-use conditions
intended conditions to which an item will be subjected during its normal working life, when used in
accordance with the manufacturer’s instructions
3.115
engineering judgement
judgement made consistent with generally accepted scientific and engineering principles and available
relevant information
[SOURCE: ISO 8178-4:2020, 3.28, modified — preferred term has been changed from "good engineering
judgement" to "engineering judgement".]

ISO/DIS 13943:2026(en)
3.116
environment
conditions and surroundings that can influence the behaviour of an item or persons when exposed to
fire (3.146)
3.117
environmental impact
significant change to the natural environment, whether adverse or beneficial, wholly or partially resulting
from a fire (3.146)
3.118
equivalence ratio
fuel (3.212)/air ratio divided by the fuel/air ratio required for a stoichiometric mixture (3.414)
Note 1 to entry: Compare with the terms fuel-lean combustion (3.214), fuel-rich combustion (3.215), stoichiometric
combustion (3.411) and stoichiometric mixture (3.414).
Note 2 to entry: Standard dry air contains 20,95 % oxygen by volume. In practice, the oxygen concentration (3.69) in
entrained air can vary and calculation of the equivalence ratio to a standard dry air basis will be required.
Note 3 to entry: The equivalent ratio is dimensionless.
3.119
error
recognizable deficiency in any phase or activity of assessment that is not due to lack of knowledge
Note 1 to entry: Error is seen not only as an error in any calculation method, but also as measurement error.
3.120
escape
effective action taken to reach a safe refuge (3.376) or place of safety (3.335)
3.121
evacuation
dispersal or removal of people from dangerous areas and their arrival at a place of relative safety or a place
of safety (3.358)
[SOURCE: ISO/TR 24188:2022, 3.1.3, modified.]
3.122
evacuation behaviour
human behaviour in fire (3.148) which enables occupants (3.321) of a building to reach a place of relative
safety or a place of safety (3.335)
Note 1 to entry:
...