SIST EN 13237:2024

SLOVENSKI STANDARD
01-december-2024
Potencialno eksplozivne atmosfere - Izrazi in definicije za opremo in zaščitne
sisteme, namenjene za uporabo v potencialno eksplozivnih atmosferah
Potentially explosive atmospheres - Terms and definitions for equipment and protective
systems intended for use in potentially explosive atmospheres
Explosionsgefährdete Bereiche - Begriffe für Geräte und Schutzsysteme zur
Verwendung in explosionsgefährdeten Bereichen
Atmosphères explosibles - Termes et définitions pour les appareils et systèmes de
protection destinés à être utilisés en atmosphères explosibles
Ta slovenski standard je istoveten z: EN 13237:2024
ICS:
01.040.13 Okolje. Varovanje zdravja. Environment. Health
Varnost (Slovarji) protection. Safety
(Vocabularies)
01.040.29 Elektrotehnika (Slovarji) Electrical engineering
(Vocabularies)
13.230 Varstvo pred eksplozijo Explosion protection
29.260.20 Električni aparati za Electrical apparatus for
eksplozivna ozračja explosive atmospheres
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN 13237
EUROPEAN STANDARD
NORME EUROPÉENNE
October 2024
EUROPÄISCHE NORM
ICS 01.040.13; 01.040.29; 13.230; 29.260.20 Supersedes EN 13237:2012
English Version
Potentially explosive atmospheres - Terms and definitions
for equipment and protective systems intended for use in
potentially explosive atmospheres
Atmosphères explosibles - Termes et définitions pour Explosionsgefährdete Bereiche - Begriffe für Geräte
les appareils et systèmes de protection destinés à être und Schutzsysteme zur Verwendung in
utilisés en atmosphères explosibles explosionsgefährdeten Bereichen
This European Standard was approved by CEN on 12 August 2024.

CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this
European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references
concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN
member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by
translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management
Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and
United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2024 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN 13237:2024 E
worldwide for CEN national Members.

Contents Page
European foreword . 3
Introduction . 4
1 Scope . 5
2 Normative references . 5
3 Terms and definitions . 5
Annex A (informative) Definitions from Directive 2014/34/EU and corrigenda . 28
Annex B (informative) Significant changes between this document and EN 13237:2012 . 31
Annex ZA (informative) Relationship between this European Standard and the essential
requirements of Directive 2014/34/EU aimed to be covered . 36
Bibliography . 37
European foreword
This document (EN 13237:2024) has been prepared by Technical Committee CEN/TC 305 “Potentially
explosive atmospheres - Explosion prevention and protection”, the secretariat of which is held by DIN.
This European Standard shall be given the status of a national standard, either by publication of an
identical text or by endorsement, at the latest by April 2025, and conflicting national standards shall be
withdrawn at the latest by April 2025.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
This document supersedes EN 13237:2012.
The significant technical changes between this document and EN 13237:2012 are given in Annex B,
Table B.1.
This document has been prepared under a standardization request addressed to CEN by the European
Commission. The Standing Committee of the EFTA States subsequently approves these requests for its
Member States.
For relationship with EU Legislation, see informative Annex ZA, which is an integral part of this document.
Any feedback and questions on this document should be directed to the users’ national standards body.
A complete listing of these bodies can be found on the CEN website.
According to the CEN-CENELEC Internal Regulations, the national standards organisations of the
following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Croatia,
Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland,
Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of North
Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and the United
Kingdom.
Introduction
This document has been produced to assist designers, manufacturers and other interested parties to use
harmonized terms and definitions (vocabulary) for equipment and protective systems intended for use
in potentially explosive atmospheres. It describes the vocabulary to be used to give all standards in this
area an overall uniformity of terminology. Throughout this document, the only hazard considered is the
explosion of an explosive atmosphere.
1 Scope
This document specifies terms and definitions (vocabulary) to be used in suitable standards dealing with
equipment and protective systems intended for use in potentially explosive atmospheres within the
scope of Directive 2014/34/EU.
NOTE Terms and definitions avoid misunderstandings that are important in relation to the essential health
and safety requirements of Directive 2014/34/EU.
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 terminology databases for use in standardization at the following addresses:
— IEC Electropedia: available at https://www.electropedia.org/
— ISO Online browsing platform: available at https://www.iso.org/obp
3.1
air flow velocity
3 2
volume of air [m ] which flows through a defined surface [m ] per unit time [s]
[SOURCE: EN 17077:2018, 3.1]
3.2
ambient atmosphere
normal atmosphere surrounding the equipment and protective system
3.3
ambient temperature
temperature of the air or other media, in the immediate vicinity of the equipment or component
, 3.1, modified – Note 1 to entry, Note 2 to entry and Note 3 to entry have
[SOURCE: EN IEC 60079-0:2018
been removed]
3.4
atmospheric conditions
conditions with pressures ranging from 80 kPa to 110 kPa and temperatures ranging from −20°C to
+60°C
[SOURCE: EN ISO 16852:2016, 3.25]
Note 1 to entry: EN ISO 16852 will be replaced by EN ISO/IEC 80079-49 .

As impacted by EN IEC 60079-0:2018/AC:2020-02 and EN IEC 60079-0:2018/A11:2024.
To be published. Stage at the time of publication: FprEN ISO/IEC 80079-49.
3.5
combustible dust
finely divided solid particles, 500 µm or less in nominal size, which can form explosive mixtures with air
at standard atmospheric pressure and temperatures
Note 1 to entry: This includes dust and grit as defined in ISO 4225:2020.
Note 2 to entry: The term “solid particles” is intended to address particles in the solid phase but does not preclude
a hollow particle.
[SOURCE: EN ISO/IEC 80079-20-2:2016 , 3.1, modified — “may” has been replaced with “can”; reference
date in Note 1 to entry has been updated]
3.5.1
conductive dust
combustible metal dusts and other combustible dusts with electrical resistivity equal to or less than
1 × 10 Ω m
Note 1 to entry: Metal dust is treated as conductive dust because it is assumed that surface oxidation cannot be
depended upon to always ensure electrical resistivity greater than 1 × 10 Ω m
[SOURCE: EN ISO/IEC 80079-20-2:2016 , 3.1.1
3.5.2
non-conductive dust
combustible dust with electrical resistivity greater than 1 × 10 Ω m
[SOURCE: EN ISO/IEC 80079-20-2:2016 , 3.1.2]
3.6
combustible flyings
solid particles, including fibres, where one dimension is greater than 500 μm in nominal size, which may
form an explosive mixture with air at standard atmospheric pressure and temperature
Note 1 to entry: The ratio of length to width is 3 or more.
Note 2 to entry: Examples of flyings include carbon fibre, rayon, cotton (including cotton linters and cotton
waste), sisal, jute, hemp, cocoa fibre, oakum and baled waste kapok.
[SOURCE: EN ISO/IEC 80079-20-2:2016 , 3.2]
3.7
constructional safety “c”
ignition protection where constructional measures are applied so as to protect against the possibility of
ignition from hot surfaces, sparks and adiabatic compression generated by moving parts
[SOURCE: EN ISO 80079-37:2016, 3.1]

As impacted by EN ISO/IEC 80079-20-2:2016/AC:2017.
3.8
control of ignition source “b”
ignition protection where mechanical or electrical devices are used in conjunction with nonelectrical
equipment to manually or automatically reduce the likelihood of a potential ignition source from
becoming an effective ignition source
Note 1 to entry: This might for example be a level sensor used to indicate loss of oil, a temperature sensor to
indicate a hot bearing or a speed sensor to indicate over-speed.
[SOURCE: EN ISO 80079-37:2016, 3.3]
3.9
control measure
3.9.1
automatic control measure
action taken without manual intervention, to reduce the likelihood of a potential ignition source from
becoming an effective ignition source
[SOURCE: EN ISO 80079-37:2016, 3.3.1]
3.9.2
manual control measure
action taken by a person as a result of a warning, indication, or alarm, to reduce the likelihood of a
potential ignition source from becoming an effective ignition source
[SOURCE: EN ISO 80079-37:2016, 3.3.2]
3.10
ignition prevention device
ignition prevention system
arrangement that converts signals from one or more sensors into an action, or indication, to reduce the
likelihood of a potential ignition source from becoming an effective ignition source
[SOURCE: EN ISO 80079-37:2016, 3.3.3, modified – “ignition prevention devices/systems” has been
replaced with “ignition prevention device” and “ignition prevention system”]
3.11
safety device
device intended for use inside or outside explosive atmospheres but required for or contributing to the
safe functioning of equipment and protective systems with respect to the risks of explosion
[SOURCE: EN ISO 80079-37:2016, 3.3.4, modified – “devices” has been replaced with “device” (twice)]
3.12
continuous grade of release
release which is continuous or is expected to occur frequently or for long periods
[SOURCE: EN IEC 60079-10-1:2021, 3.4.2, modified – Note 1 to entry has been deleted]
3.13
deflagration
explosion propagating at subsonic velocity
[SOURCE: ISO 8421-1:1987, 1.11]
3.14
degree of protection
extent of protection provided by an enclosure against access to hazardous parts, against ingress of solid
foreign objects and/or ingress of water and verified by standardised test methods
[SOURCE: EN 60529:1991 , 3.3]
3.15
detonation
explosion propagating at supersonic velocity and characterised by a shock wave
[SOURCE: ISO 8421-1:1987, 1.12]
3.16
dust
small solid particles in the atmosphere which settle out under their own weight, but which may remain
suspended in air for some time
Note 1 to entry: Generally combustible dusts with a median value of the particle diameter below 500 µm may
form explosible dust/air-mixtures.
[SOURCE: EN 14034-1:2004+A1:2011, 3.1, modified — Note 1 to entry has been changed]
3.17
electrical equipment
items applied as a whole or in part for the utilisation of electrical energy
Note 1 to entry: These include, among others, items for the generation, transmission, distribution, storage,
measurement, regulation, conversion and consumption of electrical energy and items for telecommunications.
[SOURCE: EN IEC 60079-0:2018 , 3.31.1]
3.18
electrostatic leakage resistance
electrical resistance measured between an object and earth
[SOURCE: EN 14983:2007, 3.1]
3.19
enclosure (of equipment or protective system)
all the walls including doors, covers, cable entries, rods, spindles and shafts which contribute to the type
of protection and/or their degree of protection (IP)

As impacted by EN 60529:1991/A1:2000, EN 60529:1991/A2:2013, EN 60529:1991/AC:2016-12 and
EN 60529:1991/corrigendum May 1993.
3.20
equipment grouping
classification system of equipment related to the explosive atmosphere for which they are intended to be
used
[SOURCE: EN IEC 60079-0:2018 , 3.32, modified – Note 1 to entry deleted]
3.21
Ex Component
part of Ex Equipment or a module, marked with the symbol “U”, which is not intended to be used alone
and requires additional consideration when incorporated into Ex Equipment or systems for use in
explosive atmospheres
[SOURCE: EN ISO 80079-36:2016 , 3.9]
3.22
Ex Equipment
equipment where measures have been applied to ensure that effective ignition sources are mitigated as
required by the Equipment Protection Level (EPL)
Note 1 to entry: This includes the ignition hazard assessment and/or protective measures in accordance with
EN ISO 80079 36:2016.
[SOURCE: EN ISO 80079-36:2016 , 3.11, modified – in the Note 1 to entry “this standard” has been
replaced with the standard reference]
3.23
explosion
sudden increase of pressure and temperature, due to oxidation or other exothermic reaction
[SOURCE: EN ISO/IEC 80079-38:2016 , 3.6]
3.24
explosion region
area inside the boundary curve formed by the explosion limits of a flammable substance in various
mixtures with air and inert gas
Note 1 to entry: In many cases the air concentration at the apex of the boundary curve corresponds to the limiting
air concentration, LAC.
Note 2 to entry: In many cases this is also called explosion range.

As impacted by EN ISO 80079-36:2016/AC:2019.
As impacted by EN ISO/IEC 80079-38:2016/A1:2018.
Key
1 explosion region
2 apex
3 stoichiometric line
x molar fraction in %
IN inert gas
TS test substance
a air
LAC Limiting air concentration
LEL Lower explosion limit
UEL Upper explosion limit
Figure 1 — Explosion region for a ternary system of test substance, air and inert gas
3.25
explosion diverter
passive device typically installed in a duct preventing flame jet ignition, pressure piling and reducing the
probability of flame transmission into connected equipment
3.26
explosion isolation flap valve
valve containing a flap which is fixed to the housing on an axis perpendicular to the flow direction, kept
open by the process flow and able to stop explosions from propagating through pipelines in the direction
opposite to the normal process flow through the valve
[SOURCE: EN 16447:2014, 3.1, modified — Note 1 to entry has been deleted]
3.27
explosion isolation system
3.27.1
active explosion isolation system
protective system which is designed to stop explosions from travelling through pipelines and is activated
by detectors and control and indicating equipment (CIE) which are inherent parts of the system
[SOURCE: EN 15089:2009, 3.7.1, modified — definition has been changed]
3.27.2
passive explosion isolation system
protective system which is designed to stop explosions from travelling through pipelines and does not
require detectors and a control and indicating equipment (CIE)
[SOURCE: EN 15089:2009, 3.7.2, modified — definition has been changed]
3.28
explosion limits
3.28.1
lower explosion limit
LEL
lowest concentration of the explosion range
Note 1 to entry: Those concentrations are given at which an explosion just fails during the tests.
[SOURCE: EN 1839:2017, 3.3, modified – Note 1 to entry]
3.28.2
upper explosion limit
UEL
highest concentration of the explosion range
Note 1 to entry: Those concentrations are given at which an explosion just fails during the tests.
[SOURCE: EN 1839:2017, 3.4, modified – Note 1 to entry]
3.29
explosion points
3.29.1
lower explosion point
temperature of a flammable liquid at which the concentration of the saturated vapour in air is equal to
the lower explosion limit
3.29.2
upper explosion point
temperature of a flammable liquid at which the concentration of the saturated vapour in air is equal to
the upper explosion limit
3.30
explosion pressure
p
ex
highest pressure occurring in a closed vessel during the explosion of a specific mixture of flammable
substances with air or air and inert gases determined under specified test conditions
Note 1 to entry: pex is expressed as absolute pressure with gases and vapour and as overpressure with dusts.
[SOURCE: EN 15967:2022, 3.1, modified - Note 1 to entry has been modified]
3.30.1
maximum explosion pressure
p
max
maximum value of explosion pressure measured in the tests for explosion pressure when the content of
the flammable substances in the mixture is varied
Note 1 to entry: pmax is expressed as absolute pressure with gases and vapour and as overpressure with dusts.
[SOURCE: EN 15967:2022, 3.2, modified - Note 1 to entry has been modified]
3.30.2
rate of explosion pressure rise
(dp/dt)
ex
highest value of the slope (first derivative) of the pressure-time curve (smoothed if necessary), measured
in a closed vessel during the explosion of a specific mixture of flammable substances with air or air and
inert substances determined under specified test conditions
[SOURCE: EN 15967:2022, 3.3]
3.30.3
maximum rate of explosion pressure rise
(dp/dt)
max
maximum value of the explosion pressure rise per unit time measured in the tests when the content of
the flammable substances in the mixture is varied
[SOURCE: EN 15967:2022, 3.4, modified — Note 1 to entry has been deleted]
3.31
explosion resistant
property of vessels and equipment designed to be either explosion-pressure-resistant or explosion-
pressure-shock resistant
3.31.1
explosion-pressure-resistant
property of vessels and equipment designed to withstand the expected explosion pressure without
becoming permanently deformed
3.31.2
explosion-pressure-shock resistant
property of vessels and equipment designed to withstand the expected explosion pressure without
rupturing, but allowing permanent deformation
3.32
explosion suppression
technique limiting and/or avoiding the destructive effect of an explosion by the deployment of
suppressant
[SOURCE: EN 14373:2021, 3.8]
3.33
explosion suppression system
arrangement comprising one or more explosion detectors, control and indicating equipment and one or
more high rate discharge suppressors aiming at achieving explosion suppression
[SOURCE: EN 14373:2021, 3.9]
3.34
explosion venting
protective measure which will prevent the explosion pressure in a vessel or other closed volume from
exceeding the vessel design strength by exhausting the explosion through an explosion venting device in
the vessel walls
[SOURCE: EN 14797:2006, 3.3]
3.35
explosion venting device
device which protects a vessel or other closed volume by explosion venting
[SOURCE: EN 14797:2006, 3.4]
3.36
hazardous explosive atmosphere
explosive atmosphere which causes harm, if it explodes
3.37
explosive dust atmosphere
mixture with air, under atmospheric conditions, of combustible substances in the form of dust, fibres, or
flyings which, after ignition, permits self-sustaining propagation
[SOURCE: EN ISO/IEC 80079-20-2:2016 , 3.3]
3.38
minimum ignition temperature of a dust cloud
lowest temperature of a hot surface on which the most ignitable mixture of the dust with air is ignited
under specified test conditions
[SOURCE: EN ISO/IEC 80079-20-2:2016 , 3.5]
3.39
minimum ignition temperature of a dust layer
lowest temperature of a hot surface at which ignition occurs in a dust layer under specified test conditions
[SOURCE: EN ISO/IEC 80079-20-2:2016 , 3.4]
3.40
minimum ignition energy (of a combustible dust/air mixture)
lowest electrical energy stored in a capacitor which upon discharge is sufficient to effect ignition of the
most sensitive dust/air mixture under specified test conditions
[SOURCE : EN ISO/IEC 80079-20-2:2016 , 3.6]
3.41
extinguishing barrier
active explosion isolation system that is used to discharge suppressant agent into ductwork to isolate a
flame and keep it from propagating to other process areas
[SOURCE: EN 15089:2009, 3.11, modified — definition has been changed]
3.42
flame arrester
device fitted to the opening of an enclosure or to the connecting pipework of a system of enclosures and
whose intended function is to allow flow, but prevent the transmission of flame
Note 1 to entry: This device should not be confused with a fire barrier, which is ineffective in case of explosion.
[SOURCE: EN ISO 16852:2016, 3.1, modified – Note 1 to entry has been added]
3.43
flame arrester element
portion of a flame arrester whose principal function is to prevent flame transmission
[SOURCE: EN ISO 16852:2016, 3.3]
3.44
flameless explosion venting
explosion venting protective measure which will in addition prevent the transmission of flames and
reduce the external explosion effects
Note 1 to entry: Examples of external explosion effects are: temperature, pressure and dust/combustion
products.
[SOURCE: EN 16009:2011, 3.1]
3.45
flameless explosion venting device
device which protects a vessel or other closed volume by flameless explosion venting
[SOURCE: EN 16009:2011, 3.2]
3.46
flameproof enclosure
type of protection in which the parts which can ignite an explosive atmosphere are placed in an enclosure
which can withstand the pressure developed during an internal explosion of an explosive mixture and
which prevents the transmission of the explosion to the explosive atmosphere surrounding the enclosure
3.47
flameproof joint
place where the corresponding surfaces of two parts of an enclosure, or the conjunction of enclosures,
come together and which prevents the transmission of an internal explosion to the explosive gas
atmosphere surrounding the enclosure
[SOURCE: EN 60079-1:2014 , 3.3]
3.47.1
gap of flameproof joint i
distance between the corresponding surfaces of a flameproof joint when the electrical apparatus
enclosure has been assembled
Note 1 to entry: For cylindrical surfaces, forming cylindrical joints, the gap is the difference between the
diameters of the bore and the cylindrical component.
[SOURCE: EN 60079-1:2014 , 3.6]
3.47.2
width of a flameproof joint L
shortest path through a flameproof joint from the inside to the outside of an enclosure
Note 1 to entry: This definition does not apply to threaded joints.
[SOURCE: EN 60079-1:2014 , 3.4]
3.48
flame velocity
S
f
velocity of a flame front relative to a fixed reference point
[SOURCE: EN 15089:2009, 3.14]
3.49
flammable gas or vapour
gas or vapour which, when mixed with air in certain proportions, will form an explosive gas atmosphere
[SOURCE: EN IEC 60079-10-1:2021, 3.6.4]
3.50
flammable liquid
liquid capable of producing a flammable vapour under any foreseeable operating conditions
[SOURCE: EN IEC 60079-10-1:2021, 3.6.2, modified — original Notes to entry deleted]
3.51
flammable mist
droplets of liquid, dispersed in air so as to form an explosive atmosphere
[SOURCE: EN IEC 60079-10-1:2021, 3.6.5]

As impacted by EN 60079-1:2014/AC:2018-09 and EN 60079-1:2014/A11:2024.
3.52
flammable substance
combustible substance
substance in the form of gas, vapour, liquid, solid or mixtures of these, able to undergo an exothermic
reaction with air when ignited
Note 1 to entry: For solids the term combustible substance is preferred; for gas, vapour and liquids the term
flammable substance is preferred.
3.53
flash point
FP
lowest liquid temperature at which, under specified test conditions, a liquid gives off vapours in quantity
such as to be capable of forming an ignitable vapour-air mixture
[SOURCE: EN ISO/IEC 80079-20-1:2019, 3.8]
3.54
flammable limits
lower flammable limit (LFL) and upper flammable limit (UFL) of gas in a gas-air mixture, between which
a flammable mixture is formed
Note 1 to entry: The term “explosive limits” is used especially in European standardization and regulations
interchangeably to describe these limits.
Note 2 to entry: The concentration can be expressed as either a volume fraction or a mass per unit volume.
[SOURCE: EN ISO/IEC 80079-20-1:2019, 3.6]
3.54.1
lower flammable limit
LFL
concentration of flammable gas or vapour in air, below which an explosive gas atmosphere does not form
Note 1 to entry: For the purposes of Ex Equipment, this was previously referred to as the lower explosive limit
(LEL).
Note 2 to entry: The concentration can be expressed as either a volume fraction or a mass per unit volume.
[SOURCE: EN ISO/IEC 80079-20-1:2019, 3.6.1]
3.54.2
upper flammable limit
UFL
concentration of flammable gas or vapour in air, above which an explosive gas atmosphere does not form
Note 1 to entry: For the purposes of Ex Equipment, this was previously referred to as the upper explosive limit
(UEL).
Note 2 to entry: The concentration can be expressed as either a volume fraction or a mass per unit volume.
[SOURCE: EN ISO/IEC 80079-20-1:2019, 3.6.2]
3.55
functional safety
part of the overall safety relating to the intended use in terms of the function and integrity of the
protective system including any safety related devices that are part of the protective system performance
Note 1 to entry: Functional safety covers all aspects where safety depends on the correct functioning of the
protective system and other technology safety-related systems.
Note 2 to entry: This definition deviates from the definition in EN 61508-4:2010, 3.1.12 to reflect differences in
explosion safety terminology.
[SOURCE: EN 15233:2007, 3.2, modified - year of release of EN 61508-4 has been added to Note 2 to
entry]
3.55.1
functional safety estimation
determination of the probability of occurrence of the failures violating the functional safety of the
protective system
[SOURCE: EN 15233:2007, 3.4]
3.55.2
functional safety evaluation
procedure to determine whether the functional safety of the protective system meets the predefined
acceptance criteria
[SOURCE: EN 15233:2007, 3.5]
3.56
gas
gaseous phase of a substance that cannot reach equilibrium with its liquid or solid state in the
temperature and pressure range of interest
Note 1 to entry: This is a simplification of the scientific definition, and merely requires that the substance is
above its boiling point or sublimation point at the ambient temperature and pressure.
[SOURCE: EN ISO/IEC 80079-20-1:2019, 3.9]
3.57
gas explosion constant
K
G
maximum value of the pressure rise per unit time (d /d ) during the explosion of a specific explosive
p t max
atmosphere involving gas or vapour in a closed vessel under specified test conditions normalised to a
3 1/3
vessel volume of 1 m multiplied by V
[SOURCE: EN 14491:2012, 3.5]
3.58
geometric vent area
A
v
ratio of required vent area A and venting efficiency E for the venting device
f
Note 1 to entry: The geometric vent area is the minimum cross-sectional flow area of the vent opening, taking
into consideration the possible reduction of the cross section, e.g. by back pressure supports, retaining devices and
parts of the explosion venting device which remain after bursting or venting.
[SOURCE: EN 14491:2012, 3.6]
3.59
glowing
combustion with light emission without visible flame
[SOURCE: EN 17077:2018, 3.6]
3.60
hybrid mixture
mixture of flammable substances in different physical states with air
3.61
ignition
initiation of combustion
[SOURCE: EN 17077:2018, 3.3]
3.61.1
auto-ignition
reaction which is evidenced by a clearly perceptible flame and/or explosion, and for which the ignition
delay time does not exceed 5 min
Note 1 to entry: For test procedure see EN ISO/IEC 80079-20-1:2019, 7.2.2
Note 2 to entry: This definition is only valid for gases and vapours according to the scope of the source standard.
[SOURCE: EN ISO/IEC 80079-20-1:2019, 3.1, modified – Note 2 to entry has been added.]
3.61.2
auto-ignition temperature
AIT
lowest temperature (of a surface) at which under specified test conditions an ignition of a flammable gas
or vapour in mixture with air or air-inert gas occurs
Note 1 to entry: For test procedure see EN ISO/IEC 80079-20-1:2019, Clause 7.
[SOURCE: EN ISO/IEC 80079-20-1:2019, 3.3]
3.61.3
ignition delay time
time between the completed injection of the flammable material and the ignition
[SOURCE: EN ISO/IEC 80079-20-1:2019, 3.2]
3.62
ignition hazard
occurrence of a potential ignition source that is capable of igniting an explosive atmosphere
[SOURCE: EN 15198:2007, 3.2]
3.63
ignition risk
probability of occurrence of an ignition source that is capable of igniting an explosive atmosphere
[SOURCE: EN 15198:2007, 3.1]
3.63.1
ignition risk estimation
determination of the probability of the occurrence of an ignition source
[SOURCE: EN 15198:2007, 3.5]
3.63.2
ignition risk evaluation
procedure to determine whether the intended level of protection (related to the equipment category) has
been achieved
[SOURCE: EN 15198:2007, 3.6]
Figure 2 — Relationship between ignition source definitions
3.64
ignition source scenarios
3.64.1
possible ignition source
type of ignition sou
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