SIST EN 1127-1:2019
(Main)Explosive atmospheres - Explosion prevention and protection - Part 1: Basic concepts and methodology
Explosive atmospheres - Explosion prevention and protection - Part 1: Basic concepts and methodology
This document specifies methods for the identification and assessment of hazardous situations leading to explosion and the design and construction measures appropriate for the required safety. This is achieved by: - risk assessment; - risk reduction. The safety of equipment, protective systems and components can be achieved by eliminating hazards and/or limiting the risk, i.e. by: a) appropriate design (without using safeguarding); b) safeguarding; c) information for use; d) any other preventive measures. Measures in accordance with a) (prevention) and b) (protection) against explosions are dealt with in Clause 6, measures according to c) against explosions are dealt with in Clause 7. Measures in accordance with d) are not specified in this document. They are dealt with in EN ISO 12100:2010, Clause 6. The preventive and protective measures described in this document will not provide the required level of safety unless the equipment, protective systems and components are operated within their intended use and are installed and maintained according to the relevant codes of practice or requirements. This document specifies general design and construction methods to help designers and manufacturers in achieving explosion safety in the design of equipment, protective systems and components. This document is applicable to any equipment, protective systems and components intended to be used in potentially explosive atmospheres, under atmospheric conditions. These atmospheres can arise from flammable/combustible substances processed, used or released by the equipment, protective systems and components or from materials in the vicinity of the equipment, protective systems and components and/or from the materials of construction of the equipment, protective systems and components. This document is applicable to equipment, protective systems and components at all stages of its use. This document is only applicable to equipment group II which is intended for use in other places than underground parts of mines and those parts of surface installations of such mines endangered by firedamp and/or combustible dust. This document is not applicable to: 1) medical devices intended for use in a medical environment; 2) equipment, protective systems and components where the explosion hazard results exclusively from the presence of explosive substances or unstable chemical substances; 3) equipment, protective systems and components where the explosion can occur by reaction of substances with other oxidizers than atmospheric oxygen or by other hazardous reactions or by other than atmospheric conditions; 4) equipment intended for use in domestic and non-commercial environments where potentially explosive atmospheres may only rarely be created, solely as a result of the accidental leakage of fuel gas; 5) personal protective equipment covered by Regulation (EU) 2016/425; 6) seagoing vessels and mobile offshore units together with equipment on board such vessels or units; 7) means of transport, i.e. vehicles and their trailers intended solely for transporting passengers by air or by road, rail or water networks, as well as means of transport insofar as such means are designed for transporting goods by air, by public road or rail networks or by water; vehicles intended for use in a potentially explosive atmosphere shall not be excluded; 8) the design and construction of systems containing desired, controlled combustion processes, unless they can act as ignition sources in potentially explosive atmospheres.
Explosionsfähige Atmosphären - Explosionsschutz - Teil 1: Grundlagen und Methodik
Diese Europäische Norm legt Verfahrensweisen zum Erkennen und Bewerten von gefährlichen Situationen fest, die zu Explosionen führen können, und beschreibt geeignete Planungs- und Fertigungsmaßnahmen, um die erforderliche Sicherheit zu erreichen. Das wird erreicht durch:
- Risikobewertung;
- Risikoverringerung.
Die Sicherheit von Geräten, Schutzsystemen und Komponenten lässt sich durch Beseitigen von Gefährdungen und/oder Begrenzung des Risikos erreichen, d. h. durch:
a) geeignete konstruktive Auslegung (ohne Anwendung von technischen Schutzmaßnahmen);
b) technische Schutzmaßnahmen;
c) Benutzerinformation;
d) sonstige Vorsichts- und Sicherheitsmaßnahmen.
Maßnahmen nach a) (Vorbeugung) und b) (Schutz) werden in Abschnitt 6 behandelt, Maßnahmen nach c) gegen Explosionen werden in Abschnitt 7 behandelt. Maßnahmen nach d) sind in dieser Europäischen Norm nicht festgelegt. Sie werden in EN ISO 12100:2010, Abschnitt 6 behandelt.
Die in dieser Europäischen Norm beschriebenen Schutzmaßnahmen führen nur dann zu der erforderlichen Sicherheit, wenn die Geräte, Schutzsysteme und Komponenten bestimmungsgemäß betrieben und entsprechend den für sie geltenden Anwendungsregeln oder Anforderungen installiert und gewartet werden.
Diese Norm legt allgemeine Verfahrensweisen für Entwurf und Ausführung fest, um Konstrukteure und Hersteller bei Entwurf und Ausführung von Geräten, Schutzsystemen und Komponenten in Bezug auf den Explosionsschutz zu unterstützen.
Diese Europäische Norm gilt für alle Geräte, Schutzsysteme und Komponenten, die bestimmungsgemäß in explosionsgefährdeten Bereichen unter atmosphärischen Bedingungen eingesetzt werden. Solche Bereiche können vorliegen, wenn brennbare Stoffe verarbeitet, verwendet oder von den Geräten, Schutzsystemen und Komponenten oder von Stoffen in der Umgebung von Geräten, Schutzsystemen und Komponenten und/oder aus den Konstruktionswerkstoffen der Geräte, Schutzsysteme und Komponenten freigesetzt werden.
Diese Europäische Norm gilt für Geräte, Schutzsysteme und Komponenten in allen Anwendungsphasen.
Diese Europäische Norm ist nur anwendbar auf die Gerätegruppe II für den bestimmungsgemäßen Gebrauch an anderen Orten als in Untertagebereichen von Bergwerken und außerhalb derartiger Einrichtungen von Bergwerken über Tage, die durch Schlagwetter und/oder brennbaren Staub gefährdet sind.
Diese Europäische Norm ist nicht anwendbar auf:
1) medizinische Geräte zur bestimmungsgemäßen Verwendung in medizinischen Bereichen;
2) Geräte, Schutzsysteme und Komponenten, bei denen die Explosionsgefahr ausschließlich durch die Anwesenheit von Sprengstoffen oder chemisch instabilen Stoffen hervorgerufen wird;
3) Geräte, Schutzsysteme und Komponenten, bei denen die Explosion durch Reaktion von Stoffen mit anderen Oxidationsmitteln als Luftsauerstoff oder durch andere gefährliche Reaktionen oder andere als atmosphärische Bedingungen erfolgen können;
4) Geräte, die zur Verwendung in häuslicher und nichtkommerzieller Umgebung vorgesehen sind, in der eine explosionsfähige Atmosphäre nur selten und lediglich infolge eines unbeabsichtigten Brennstoffaustritts gebildet werden kann;
5) persönliche Schutzausrüstungen im Sinne der Richtlinie 89/686/EWG;
6) Seeschiffe und bewegliche Offshore-Anlagen sowie die Ausrüstungen an Bord dieser Schiffe oder Anlagen;
7) Beförderungsmittel, d. h. Fahrzeuge und dazugehörige Anhänger, die ausschließlich für die Beförderung von Personen in der Luft, auf Straßen- und Schienennetzen oder auf dem Wasserweg bestimmt sind, und Beförderungsmittel, soweit sie für den Transport von Gütern in der Luft, auf öffentlichen Straßen- und Schienennetzen oder auf dem Wasserweg konzipiert sind; nicht ausgenommen sind Fahrzeuge, die in explosionsgefährdeten Bereichen eingesetzt werden sollen;
(...)
Atmosphères explosives - Prévention de l'explosion et protection contre l'explosion - Partie 1 : Notions fondamentales et méthodologie
La présente Norme européenne spécifie des méthodes pour identifier et évaluer les situations dangereuses conduisant à l'explosion, ainsi que les mesures de conception et de construction appropriées pour la sécurité requise. Cette sécurité est obtenue :
- en appréciant les risques ;
- en réduisant les risques.
La sécurité des appareils, systèmes de protection et composants peut être obtenue par l'élimination des phénomènes dangereux et/ou la limitation des risques, c’est-à-dire par :
a) une conception appropriée (ne nécessitant pas de dispositif de protection) ;
b) des dispositifs de protection ;
c) des informations d'utilisation ;
d) toute autre mesure de prévention.
Les mesures contre les explosions correspondant à a) (prévention) et b) (protection) sont traitées dans l'Article 6, les mesures contre les explosions correspondant à c) sont traitées dans l'Article 7. Les mesures correspondant à d) ne sont pas spécifiées dans la présente Norme européenne. Elles sont traitées dans l'EN ISO 12100:2010, Article 6.
Les mesures de prévention et de protection décrites dans la présente Norme européenne procureront le niveau de sécurité requis à condition que les appareils, systèmes de protection et composants soient utilisés conformément à leur destination et soient installés et entretenus conformément aux codes de bonnes pratiques ou aux exigences appropriés.
La présente norme spécifie des méthodes générales de conception et de construction pour aider les concepteurs et les fabricants à parvenir à une conception sécurisée contre les explosions des appareils, systèmes de protection et composants.
La présente Norme européenne est applicable à tout appareil, système de protection et composant destiné à être utilisé en atmosphères explosibles, dans les conditions atmosphériques. Ces atmosphères peuvent provenir de substances inflammables fabriquées et manipulées dans les appareils, systèmes de protection et composants ou dégagées par ceux-ci, ou de substances présentes au voisinage des appareils, systèmes de protection et composants et/ou des matériaux constitutifs des appareils, systèmes de protection et composants.
La présente Norme européenne est applicable aux appareils, aux systèmes de protection et aux composants à tous les stades de leur utilisation.
La présente Norme européenne ne s'applique qu'aux appareils du groupe II qui sont destinés à être utilisés dans des emplacements autres que les parties souterraines des mines et les parties des installations de surface de ces mines exposées aux risques de grisou et/ou de poussières inflammables.
La présente Norme européenne n'est pas applicable aux :
1) dispositifs médicaux destinés à être utilisés dans un environnement médical ;
2) appareils, systèmes de protection et composants lorsque le phénomène dangereux d'explosion est exclusivement dû à la présence de matières explosives ou de matières chimiques instables ;
3) appareils, systèmes de protection et composants lorsque l'explosion peut se produire en raison de la réaction de substances avec d'autres comburants que l'oxygène de l’atmosphère ou en raison d'autres réactions dangereuses ou encore dans des conditions autres qu'atmosphériques ;
4) équipements destinés à être utilisés dans des environnements domestiques et non commerciaux dans lesquels les atmosphères explosibles ne peuvent être produites que rarement, uniquement à la suite d'une fuite accidentelle de gaz combustible ;
5) équipements de protection individuelle couverts par la Directive 89/686/CEE ;
6) navires de mer et unités mobiles offshore ainsi qu'aux équipements à bord de ces navires ou unités ;
(...)
Eksplozivne atmosfere - Protieksplozijska zaščita - 1. del: Osnovni pojmi in metodologija
Ta dokument določa metode za ugotavljanje in ocenjevanje nevarnih okoliščin, ki lahko povzročijo eksplozije, ter strukturne in konstrukcijske ukrepe, primerne za potrebno varnost. To se doseže z: – oceno tveganja; – zmanjšanjem tveganja. Varnost opreme, zaščitnih sistemov in komponent je mogoče doseči z odpravo nevarnosti in/ali omejevanjem tveganja, tj. a) z ustreznim načrtovanjem (brez uporabe zaščite); b) z zaščito; c) z informacijami za uporabo; d) s kakršnimi koli drugimi preventivnimi ukrepi. Ukrepi v skladu z a) (preprečevanje) in b) (zaščita) proti eksploziji so obravnavani v točki 6; ukrepi v skladu s c) proti eksploziji so obravnavani v točki 7. Ukrepi v skladu z d) niso določeni v tem dokumentu. Obravnavani so v točki 6 standarda EN ISO 12100:2010. Preventivni in zaščitni ukrepi, opisani v tem dokumentu, ne zagotavljajo zahtevane ravni varnosti, razen če se oprema, zaščitni sistemi in komponente uporabljajo v skladu z njihovim namenom uporabe ter so nameščeni in vzdrževani v skladu z ustreznimi kodeksi ravnanja ali zahtevami. Ta dokument določa splošne metode za načrtovanje in konstruiranje, ki bodo projektantom in proizvajalcem v pomoč pri doseganju protieksplozivne zaščite pri načrtovanju opreme, zaščitnih sistemov in komponent. Ta dokument se uporablja za vso opremo, zaščitne sisteme in komponente, ki so namenjeni za uporabo v potencialno eksplozivnih atmosferah v atmosferskih pogojih. Te atmosfere lahko nastanejo iz vnetljivih/gorljivih snovi, ki jih obdelujejo, uporabljajo ali sproščajo oprema, zaščitni sistemi in komponente, iz materialov v bližini opreme, zaščitnih sistemov in komponent, in/ali iz konstrukcijskih materialov opreme, zaščitnih sistemov in komponent. Ta dokument se uporablja za opremo, zaščitne sisteme in komponente na vseh stopnjah uporabe. Ta dokument se uporablja samo za opremo skupine II, ki je namenjena uporabi na mestih, ki niso podzemni deli rudnikov in deli površinskih instalacij takih rudnikov, ki jih ogroža jamski eksplozivni plin in/ali vnetljiv prah. Ta dokument se ne uporablja za: 1) medicinske pripomočke, namenjene uporabi v medicinskem okolju; 2) opremo, zaščitne sisteme in komponente, pri katerih je nevarnost eksplozije izključno posledica navzočnosti eksplozivnih snovi ali nestabilnih kemikalij; 3) opremo, zaščitne sisteme in komponente, pri katerih je eksplozija lahko posledica reakcije snovi z oksidantom, razen atmosferskega kisika, ali drugih nevarnih reakcij ali pogojev, razen atmosferskih pogojev; 4) oprema, namenjena za uporabo v domačem in nekomercialnem okolju, pri kateri eksplozivna atmosfera nastane zelo redko, in sicer izključno zaradi naključnega uhajanja kurilnega plina; 5) osebno zaščitno opremo, zajeto z Direktivo(EU) 2016/425; 6) pomorska plovila in premične enote na morju skupaj z opremo na krovu takšnih plovil ali enot; 7) prevozna sredstva, tj. vozila in njihove prikolice, ki so namenjeni izključno prevozu potnikov po zraku ali cesti, po železniških ali vodnih omrežjih, ter prevozna sredstva, v kolikor so ta zasnovana za prevoz blaga po zraku, javnih cestnih ali železniških omrežjih ali po vodi; vozila, ki so namenjena za uporabo v potencialno eksplozivnih atmosferah, ne smejo biti izključena; 8) projektiranje in gradnjo sistemov, ki vsebujejo želene, nadzorovane procese zgorevanja, razen če lahko delujejo kot viri vžiga v potencialno eksplozivnih atmosferah.
General Information
Relations
Standards Content (Sample)
SLOVENSKI STANDARD
SIST EN 1127-1:2019
01-december-2019
Nadomešča:
SIST EN 1127-1:2011
Eksplozivne atmosfere - Protieksplozijska zaščita - 1. del: Osnovni pojmi in
metodologija
Explosive atmospheres - Explosion prevention and protection - Part 1: Basic concepts
and methodology
Explosionsfähige Atmosphären - Explosionsschutz - Teil 1: Grundlagen und Methodik
Atmosphères explosives - Prévention de l'explosion et protection contre l'explosion -
Partie 1 : Notions fondamentales et méthodologie
Ta slovenski standard je istoveten z: EN 1127-1:2019
ICS:
13.230 Varstvo pred eksplozijo Explosion protection
SIST EN 1127-1:2019 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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SIST EN 1127-1:2019
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SIST EN 1127-1:2019
EN 1127-1
EUROPEAN STANDARD
NORME EUROPÉENNE
August 2019
EUROPÄISCHE NORM
ICS 13.230 Supersedes EN 1127-1:2011
English Version
Explosive atmospheres - Explosion prevention and
protection - Part 1: Basic concepts and methodology
Atmosphères explosives - Prévention de l'explosion et Explosionsfähige Atmosphären - Explosionsschutz -
protection contre l'explosion - Partie 1 : Notions Teil 1: Grundlagen und Methodik
fondamentales et méthodologie
This European Standard was approved by CEN on 3 June 2019.
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, Turkey 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
© 2019 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN 1127-1:2019 E
worldwide for CEN national Members.
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SIST EN 1127-1:2019
EN 1127-1:2019 (E)
Contents Page
European foreword . 4
Introduction . 5
1 Scope . 6
2 Normative references . 7
3 Terms and definitions . 7
4 Risk assessment . 8
4.1 General . 8
4.2 Identification of explosion hazards . 8
4.2.1 General . 8
4.2.2 Flammability properties . 9
4.2.3 Explosion behaviour . 9
4.2.4 Likelihood of occurrence of a hazardous explosive atmosphere . 9
4.3 Identification of ignition hazards . 10
4.3.1 General . 10
4.3.2 Ignition properties . 11
4.3.3 Likelihood of occurrence of effective ignition sources . 11
4.4 Estimation of the possible effects of an explosion . 11
5 Possible ignition sources . 12
5.1 Hot surfaces . 12
5.2 Flames and hot gases (including hot particles) . 13
5.3 Mechanically generated impact, friction and abrasion . 13
5.4 Electrical equipment and components . 14
5.5 Stray electric currents, cathodic corrosion protection . 14
5.6 Static electricity . 14
5.7 Lightning . 15
4 11
5.8 Radio frequency (RF) electromagnetic waves from 10 Hz to 3 × 10 Hz . 15
11 15
5.9 Electromagnetic waves from 3 × 10 Hz to 3 × 10 Hz . 15
5.10 Ionizing radiation. 16
5.11 Ultrasonic waves . 16
5.12 Adiabatic compression and shock waves . 16
5.13 Exothermic reactions, including self-ignition of dusts . 17
6 Risk reduction . 17
6.1 Fundamental priciples . 17
6.2 Avoidance or reduction of the amount of hazardous explosive atmospheres . 18
6.2.1 Process parameters . 18
6.2.2 Design and construction of equipment, protective systems and components . 19
6.3 Hazardous areas . 21
6.4 Requirements for the design and construction of equipment, protective systems and
components for avoidance of effective ignition sources. 21
6.4.1 General . 21
6.4.2 Hot surfaces . 22
6.4.3 Flames and hot gases . 24
2
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EN 1127-1:2019 (E)
6.4.4 Mechanically generated impact, friction and grinding . 24
6.4.5 Electrical equipment and components . 25
6.4.6 Stray electric currents and cathodic corrosion protection . 25
6.4.7 Static electricity . 26
6.4.8 Lightning . 26
4 11
6.4.9 Radio frequency (RF) electromagnetic waves from 10 Hz to 3 × 10 Hz . 27
11 15
6.4.10 Electromagnetic waves from 3 × 10 Hz to 3 × 10 Hz . 28
6.4.11 Ionizing radiation . 28
6.4.12 Ultrasonic waves . 29
6.4.13 Adiabatic compression and shock waves . 30
6.4.14 Exothermic reactions, including self-ignition of dusts . 31
6.5 Requirements for the design and construction of equipment, protective systems and
components to reduce the explosion effects . 31
6.6 Provisions for emergency measures . 32
6.7 Principles of measuring and control systems for explosion prevention and
protection . 32
7 Information for use . 33
7.1 General . 33
7.2 Information for commissioning, maintenance and repair to prevent explosion . 34
7.3 Qualifications and training . 34
Annex A (informative) Information for the use of tools in potentially explosive
atmospheres . 35
Annex B (informative) Tightness of equipment . 36
B.1 General . 36
B.2 Normal tightness . 36
B.3 Enhanced tightness . 37
Annex C (normative) Verification procedure for the threshold limit of ultrasound in liquids . 38
Annex D (informative) Significant technical changes between this document and the
previous edition of this document. 40
Annex ZA (informative) Relationship between this European Standard and the essential
requirements of EU Directive 2014/34/EU aimed to be covered . 42
Annex ZB (informative) Relationship between This document and the essential
requirements of Directive 2006/42/EC aimed to be covered . 43
Bibliography . 44
3
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SIST EN 1127-1:2019
EN 1127-1:2019 (E)
European foreword
This document (EN 1127-1:2019) 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 February 2020, and conflicting national standards
shall be withdrawn at the latest by February 2022.
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 1127-1:2011.
Annex D provides details of significant technical changes between this document and the previous
edition EN 1127-1:2011.
This document has been prepared under a standardization request given to CEN by the European
Commission and the European Free Trade Association, and supports essential requirements of
EU Directives.
For relationship with EU Directives, see informative Annex ZA and ZB, which are integral parts of this
document.
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, Turkey and the
United Kingdom.
4
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SIST EN 1127-1:2019
EN 1127-1:2019 (E)
Introduction
CEN and CENELEC are producing a set of standards to assist designers, manufacturers and other
interested bodies to interpret the essential safety requirements in order to achieve conformity with
European Legislation. Within this series of standards CEN has undertaken to draw up a standard to give
guidance in the field of explosion prevention and protection, as hazards from explosions are intended to
be considered in accordance with EN ISO 12100:2010.
In accordance with EN ISO 12100:2010, it is a type B standard.
This standard describes the basic concepts and methodology of explosion prevention and protection.
CEN/TC 305 has a mandate in this area to produce B-type, and C-type standards, which will allow
verification of conformity with the essential safety requirements.
Explosions can occur from:
a) materials processed or used by the equipment, protective systems and components;
b) materials released by the equipment, protective systems and components;
c) materials in the vicinity of the equipment, protective systems and components;
d) materials of construction of the equipment, protective systems and components.
Since safety depends not only on equipment, protective systems and components but also on the
material being handled and its use, this standard includes aspects related to the intended use and
foreseeable misuse, i.e. the manufacturer should consider in which way and for which purpose the
equipment, protective systems and components will be used and take this into account during its design
and construction. This is the only way hazards inherent in equipment, protective systems and
components can be reduced.
NOTE This standard can also serve as a guide for users of equipment, protective systems and components
when assessing the risk of explosion in the workplace and selecting the appropriate equipment, protective
systems and components.
5
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EN 1127-1:2019 (E)
1 Scope
This document specifies methods for the identification and assessment of hazardous situations leading
to explosion and the design and construction measures appropriate for the required safety. This is
achieved by:
— risk assessment;
— risk reduction.
The safety of equipment, protective systems and components can be achieved by eliminating hazards
and/or limiting the risk, i.e. by:
a) appropriate design (without using safeguarding);
b) safeguarding;
c) information for use;
d) any other preventive measures.
Measures in accordance with a) (prevention) and b) (protection) against explosions are dealt with in
Clause 6, measures according to c) against explosions are dealt with in Clause 7. Measures in
accordance with d) are not specified in this document. They are dealt with in
EN ISO 12100:2010, Clause 6.
The preventive and protective measures described in this document will not provide the required level
of safety unless the equipment, protective systems and components are operated within their intended
use and are installed and maintained according to the relevant codes of practice or requirements.
This document specifies general design and construction methods to help designers and manufacturers
in achieving explosion safety in the design of equipment, protective systems and components.
This document is applicable to any equipment, protective systems and components intended to be used
in potentially explosive atmospheres, under atmospheric conditions. These atmospheres can arise from
flammable/combustible substances processed, used or released by the equipment, protective systems
and components or from materials in the vicinity of the equipment, protective systems and components
and/or from the materials of construction of the equipment, protective systems and components.
This document is applicable to equipment, protective systems and components at all stages of its use.
This document is only applicable to equipment group II which is intended for use in other places than
underground parts of mines and those parts of surface installations of such mines endangered by
firedamp and/or combustible dust.
This document is not applicable to:
1) medical devices intended for use in a medical environment;
2) equipment, protective systems and components where the explosion hazard results exclusively
from the presence of explosive substances or unstable chemical substances;
3) equipment, protective systems and components where the explosion can occur by reaction of
substances with other oxidizers than atmospheric oxygen or by other hazardous reactions or by
other than atmospheric conditions;
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EN 1127-1:2019 (E)
4) equipment intended for use in domestic and non-commercial environments where potentially
explosive atmospheres may only rarely be created, solely as a result of the accidental leakage of fuel
gas;
5) personal protective equipment covered by Regulation (EU) 2016/425;
6) seagoing vessels and mobile offshore units together with equipment on board such vessels or units;
7) means of transport, i.e. vehicles and their trailers intended solely for transporting passengers by air
or by road, rail or water networks, as well as means of transport insofar as such means are
designed for transporting goods by air, by public road or rail networks or by water; vehicles
intended for use in a potentially explosive atmosphere shall not be excluded;
8) the design and construction of systems containing desired, controlled combustion processes, unless
they can act as ignition sources in potentially explosive atmospheres.
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.
EN 13237:2012, Potentially explosive atmospheres — Terms and definitions for equipment and protective
systems intended for use in potentially explosive atmospheres
EN 15198:2007, Methodology for the risk assessment of non-electrical equipment and components for
intended use in potentially explosive atmospheres
EN ISO 12100:2010, Safety of machinery — General principles for design — Risk assessment and risk
reduction
EN ISO 80079-36:2016, Explosive atmospheres — Part 36: Non-electrical equipment for explosive
atmospheres — Basic method and requirements
3 Terms and definitions
For the purposes of this document, the terms and definitions given in EN 13237:2012 and the following
apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
3.1
normal tightness
absence of leakage when any of the tightness tests or tightness monitorings appropriate for the
application does not reveal any hazardous leaks during normal operation
3.2
enhanced tightness
absence of leakage when due to the design and measures of maintenance any of the tightness tests or
tightness monitorings appropriate for the application does not reveal any hazardous leaks during
normal operations and expected malfunctions
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4 Risk assessment
4.1 General
For non-electrical equipment, components, protective systems, devices and assemblies of these non-
electrical products, which have their own potential ignition sources and are intended for use in
explosive atmospheres, risk assessment shall be carried out according to EN ISO 80079-36:2016. For
other situations, risk assessment shall be carried out in accordance with EN ISO 12100:2010 and/or
EN 15198:2007 unless other standards can be identified as being more appropriate, considering the
following:
a) identification of explosion hazards and determination of the likelihood of occurrence of a
hazardous explosive atmosphere (see 4.2);
b) identification of ignition hazards and determination of the likelihood of occurrence of potential
ignition sources (see 4.3);
c) estimation of the possible effects of an explosion in case of ignition (see 4.4);
d) evaluation of the risk and whether the intended level of protection has been achieved;
NOTE The intended level of protection is defined by at least legal requirements and, if necessary, additional
requirements specified by the user.
e) consideration of measures to reduce of the risks (see Clause 6).
A comprehensive approach shall be taken, especially for complex equipment, protective systems and
components, plants comprising individual units and, above all, for extended plants. This risk assessment
shall take into account the ignition and explosion hazard from:
1) the equipment, protective systems and components themselves;
2) the interaction between the equipment, protective systems and components and the substances
being handled;
3) the particular process performed in the equipment, protective systems and components;
4) the surroundings of the equipment, protective systems and components and possible interaction
with neighbouring processes.
4.2 Identification of explosion hazards
4.2.1 General
The explosion hazard is generally related to the materials and substances processed, used or released
by equipment, protective systems and components and materials used to construct equipment,
protective systems and components. Some of these released substances can undergo combustion
processes in air. These processes are often accompanied by the release of considerable amounts of heat
and can be associated with a pressure build-up and the release of hazardous materials. In contrast to
burning in a fire, an explosion is essentially a self-sustained propagation of the reaction zone (flame)
through the hazardous explosive atmosphere. This potential hazard associated with the hazardous
explosive atmosphere is released when ignited by an effective ignition source.
The safety characteristics listed in 4.2.2 and 4.2.3 describe safety relevant properties of
flammable/combustible substances. The material properties and the safety characteristics are used for
the identification of the explosion hazard.
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It is necessary to bear in mind that such safety characteristics are not constants but depend for instance
on the techniques used for their measurement. Also, for dusts, tabulated safety data are for guidance
only because the values depend on particle size and shape, moisture content and the presence of
additives even in trace concentrations. For a specific application, samples of the dust present in the
equipment should be tested and the data obtained used in the hazard identification.
4.2.2 Flammability properties
Since in this context it is not the material itself that represents the potential hazard but its contact or
mixing with air, the properties of the mixture of the flammable/combustible substance with air shall be
determined. These properties give information about a substance's burning behaviour and whether it
could give rise to fire or explosions. Relevant data are e.g.:
a) lower explosion point (see EN 15794), that can be substituted by flash point (with a safety factor), if
lower explosion point is not available;
b) explosion limits (LEL, UEL) (see EN 14034-3 and EN 1839);
NOTE Lower explosion limit (LEL) and upper explosion limit (UEL) are named lower flammability limit (LFL)
and upper flammability limit (UFL) in EN ISO/IEC 80079-20-1.
c) limiting oxygen concentration (LOC) (see EN 14034-4 and EN 1839).
4.2.3 Explosion behaviour
The behaviour of the explosive atmosphere after ignition shall be characterized by data such as:
a) maximum explosion pressure (p ) (see EN 14034-1, EN 14034-4 and EN 15967);
max
b) maximum rate of explosion pressure rise ((d /d ) ) (see EN 14034-2, EN 14491 and EN 15967);
p t max
c) maximum experimental safe gap (MESG) (see EN 60079-20-1).
4.2.4 Likelihood of occurrence of a hazardous explosive atmosphere
The likelihood of occurrence of a hazardous explosive atmosphere depends on the following:
— presence of a flammable/combustible substance;
— degree of dispersion of the flammable/combustible substance (e.g. gases, vapours, mists, dusts);
— concentration of the flammable/combustible substance in air within the explosion range;
— amount of explosive atmosphere sufficient to cause injury or damage in case of ignition.
In assessment of the likelihood of occurrence of a hazardous explosive atmosphere, possible formation
of the hazardous explosive atmosphere through chemical reactions, pyrolysis and biological processes
from the materials present shall be taken into account.
If it is impossible to estimate the likelihood of occurrence of a hazardous explosive atmosphere, the
assumption shall be made that such an atmosphere is always present.
a) Presence of a flammable/combustible substance
Flammable/combustible substances shall be considered as materials which can form a hazardous
explosive atmosphere unless an investigation of their properties has shown that in mixtures with air
they are incapable of self-sustained propagation of an explosion. In assessment of the likelihood of
occurrence of a hazardous explosive atmosphere, possible formation of the hazardous explosive
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atmosphere through chemical reactions, pyrolysis and biological processes from the materials present
shall be taken into account.
b) Degree of dispersion of flammable/combustible substances
By their very nature, gases, vapours and mists have a degree of dispersion high enough to produce a
hazardous explosive atmospher
...
SLOVENSKI STANDARD
oSIST prEN 1127-1:2018
01-januar-2018
(NVSOR]LYQHDWPRVIHUH3URWLHNVSOR]LMVND]DãþLWDGHO 2VQRYQLSRMPLLQ
PHWRGRORJLMD
Explosive atmospheres - Explosion prevention and protection - Part 1: Basic concepts
and methodology
Explosionsfähige Atmosphären - Explosionsschutz - Teil 1: Grundlagen und Methodik
Atmosphères explosives - Prévention de l'explosion et protection contre l'explosion -
Partie 1 : Notions fondamentales et méthodologie
Ta slovenski standard je istoveten z: prEN 1127-1
ICS:
13.230 Varstvo pred eksplozijo Explosion protection
oSIST prEN 1127-1:2018 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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oSIST prEN 1127-1:2018
DRAFT
EUROPEAN STANDARD
prEN 1127-1
NORME EUROPÉENNE
EUROPÄISCHE NORM
November 2017
ICS 13.230 Will supersede EN 1127-1:2011
English Version
Explosive atmospheres - Explosion prevention and
protection - Part 1: Basic concepts and methodology
Atmosphères explosives - Prévention de l'explosion et Explosionsfähige Atmosphären - Explosionsschutz -
protection contre l'explosion - Partie 1 : Notions Teil 1: Grundlagen und Methodik
fondamentales et méthodologie
This draft European Standard is submitted to CEN members for enquiry. It has been drawn up by the Technical Committee
CEN/TC 305.
If this draft becomes a European Standard, 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.
This draft European Standard was established by CEN 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, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,
Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,
Turkey and United Kingdom.
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 supporting documentation.
Warning : This document is not a European Standard. It is distributed for review and comments. It is subject to change without
notice and shall not be referred to as a European Standard.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Avenue Marnix 17, B-1000 Brussels
© 2017 CEN All rights of exploitation in any form and by any means reserved Ref. No. prEN 1127-1:2017 E
worldwide for CEN national Members.
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Contents Page
European foreword . 4
Introduction . 5
1 Scope . 6
2 Normative references . 7
3 Terms and definitions . 7
4 Risk assessment . 8
4.1 General . 8
4.2 Identification of explosion hazards . 8
4.2.1 General . 8
4.2.2 Combustion properties . 9
4.2.3 Explosion behaviour . 9
4.2.4 Likelihood of occurrence of a hazardous explosive atmosphere . 9
4.3 Identification of ignition hazards . 10
4.3.1 General . 10
4.3.2 Ignition properties . 11
4.3.3 Likelihood of occurrence of effective ignition sources . 11
4.4 Estimation of the possible effects of an explosion . 11
5 Possible ignition sources . 12
5.1 Hot surfaces . 12
5.2 Flames and hot gases (including hot particles) . 13
5.3 Mechanically generated impact, friction and grinding . 13
5.4 Electrical apparatus . 13
5.5 Stray electric currents, cathodic corrosion protection . 14
5.6 Static electricity . 14
5.7 Lightning . 14
4 11
5.8 Radio frequency (RF) electromagnetic waves from 10 Hz to 3 × 10 Hz . 15
11 15
5.9 Electromagnetic waves from 3 × 10 Hz to 3 × 10 Hz . 15
5.10 Ionizing radiation. 15
5.11 Ultrasonic waves . 16
5.12 Adiabatic compression and shock waves . 16
5.13 Exothermic reactions, including self-ignition of dusts . 16
6 Risk reduction . 17
6.1 Fundamental priciples . 17
6.2 Avoidance or reduction of the amount of explosive atmosphere . 18
6.2.1 Process parameters . 18
6.2.2 Design and construction of equipment, protective systems and components . 19
6.3 Hazardous areas . 20
6.4 Requirements for the design and construction of equipment, protective systems and
components by avoidance of effective ignition sources. 21
6.4.1 General . 21
6.4.2 Hot surfaces . 22
6.4.3 Flames and hot gases . 23
6.4.4 Mechanically generated impact, friction and grinding . 24
6.4.5 Electrical apparatus . 24
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6.4.6 Stray electric currents and cathodic corrosion protection . 24
6.4.7 Static electricity . 25
6.4.8 Lightning . 26
4 11
6.4.9 Radio frequency (RF) electromagnetic waves from 10 Hz to 3 × 10 Hz . 27
11 15
6.4.10 Electromagnetic waves from 3 × 10 Hz to 3 × 10 Hz . 27
6.4.11 Ionizing radiation . 28
6.4.12 Ultrasonics . 29
6.4.13 Adiabatic compression and shock waves . 30
6.4.14 Exothermic reactions, including self-ignition of dusts . 30
6.5 Requirements for the design and construction of equipment, protective systems and
components to reduce the explosion effects . 31
6.6 Provisions for emergency measures . 31
6.7 Principles of measuring and control systems for explosion prevention and
protection . 32
7 Information for use . 32
7.1 General . 32
7.2 Information for commissioning, maintenance and repair to prevent explosion . 33
7.3 Qualifications and training . 33
Annex A (informative) Information for the use of tools in potentially explosive
atmospheres . 34
Annex B (informative) Tightness of equipment . 35
B.1 General . 35
B.2 Normal tight equipment . 35
B.3 Enhanced tight equipment . 36
Annex C (normative) Verification procedure for the threshold limit of ultrasound in liquids . 37
Annex D (informative) Significant technical changes between this document and the
previous edition of this European Standard . 39
Annex ZA (informative) Relationship between this European Standard and the essential
requirements of EU Directive 2014/34/EU aimed to be covered . 41
Annex ZB (informative) Relationship between this European Standard and the essential
requirements of Directive 2006/42/EC aimed to be covered . 42
Bibliography . 43
3
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European foreword
This document (prEN 1127-1:2017) 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 document is currently submitted to the CEN Enquiry.
This document will supersede EN 1127-1:2011.
This document has been prepared under a mandate given to CEN by the European Commission and the
European Free Trade Association, and supports essential requirements of EU Directive(s).
For relationship with EU Directive(s), see informative Annex ZA and ZB, which are integral parts of this
document.
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Introduction
CEN and CENELEC are producing a set of standards to assist designers, manufacturers and other
interested bodies to interpret the essential safety requirements in order to achieve conformity with
European Legislation. Within this series of standards CEN has undertaken to draw up a standard to give
guidance in the field of explosion prevention and protection, as hazards from explosions are intended to
be considered in accordance with EN ISO 12100.
In accordance with EN ISO 12100, it is a type B standard.
This standard describes the basic concepts and methodology of explosion prevention and protection.
CEN/TC 305 has a mandate in this area to produce B-type, and C-type standards, which will allow
verification of conformity with the essential safety requirements.
Explosions can occur from:
a) materials processed or used by the equipment, protective systems and components;
b) materials released by the equipment, protective systems and components;
c) materials in the vicinity of the equipment, protective systems and components;
d) materials of construction of the equipment, protective systems and components.
Since safety depends not only on equipment, protective systems and components but also on the
material being handled and its use, this standard includes aspects related to the intended use and
foreseeable misuse, i.e. the manufacturer should consider in which way and for which purpose the
equipment, protective systems and components will be used and take this into account during its design
and construction. This is the only way hazards inherent in equipment, protective systems and
components can be reduced.
NOTE This standard can also serve as a guide for users of equipment, protective systems and components
when assessing the risk of explosion in the workplace and selecting the appropriate equipment, protective
systems and components.
5
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1 Scope
This European Standard specifies methods for the identification and assessment of hazardous
situations leading to explosion and the design and construction measures appropriate for the required
safety. This is achieved by:
— risk assessment;
— risk reduction.
The safety of equipment, protective systems and components can be achieved by eliminating hazards
and/or limiting the risk, i.e. by:
a) appropriate design (without using safeguarding);
b) safeguarding;
c) information for use;
d) any other preventive measures.
Measures in accordance with a) (prevention) and b) (protection) against explosions are dealt with in
Clause 6, measures according to c) against explosions are dealt with in Clause 7. Measures in
accordance with d) are not specified in this European Standard. They are dealt with in
EN ISO 12100:2010, Clause 6.
The preventive and protective measures described in this European Standard will not provide the
required level of safety unless the equipment, protective systems and components are operated within
their intended use and are installed and maintained according to the relevant codes of practice or
requirements.
This standard specifies general design and construction methods to help designers and manufacturers
in achieving explosion safety in the design of equipment, protective systems and components.
This European Standard is applicable to any equipment, protective systems and components intended
to be used in potentially explosive atmospheres, under atmospheric conditions. These atmospheres can
arise from flammable materials processed, used or released by the equipment, protective systems and
components or from materials in the vicinity of the equipment, protective systems and components
and/or from the materials of construction of the equipment, protective systems and components.
This European Standard is applicable to equipment, protective systems and components at all stages of
its use.
This European Standard is only applicable to equipment group II which is intended for use in other
places than underground parts of mines and those parts of surface installations of such mines
endangered by firedamp and/or flammable dust.
This European Standard is not applicable to:
1) medical devices intended for use in a medical environment;
2) equipment, protective systems and components where the explosion hazard results exclusively
from the presence of explosive substances or unstable chemical substances;
3) equipment, protective systems and components where the explosion can occur by reaction of
substances with other oxidizers than atmospheric oxygen or by other hazardous reactions or by
other than atmospheric conditions;
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4) equipment intended for use in domestic and non-commercial environments where potentially
explosive atmospheres may only rarely be created, solely as a result of the accidental leakage of fuel
gas;
5) personal protective equipment covered by Directive 89/686/EEC;
6) seagoing vessels and mobile offshore units together with equipment on board such vessels or units;
7) means of transport, i.e. vehicles and their trailers intended solely for transporting passengers by air
or by road, rail or water networks, as well as means of transport insofar as such means are
designed for transporting goods by air, by public road or rail networks or by water; vehicles
intended for use in a potentially explosive atmosphere shall not be excluded;
8) the design and construction of systems containing desired, controlled combustion processes, unless
they can act as ignition sources in potentially explosive atmospheres.
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.
EN 13237, Potentially explosive atmospheres - Terms and definitions for equipment and protective systems
intended for use in potentially explosive atmospheres
EN 15198, Methodology for the risk assessment of non-electrical equipment and components for intended
use in potentially explosive atmospheres
EN ISO 12100, Safety of machinery - General principles for design - Risk assessment and risk reduction
(ISO 12100)
3 Terms and definitions
For the purposes of this document, the terms and definitions given in EN 13237 and the following apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
3.1
tightness
absence of leakage greater than the specified limit
3.2
normal tightness
absence of leakage when any of the tightness tests or tightness monitorings appropriate for the
application does not reveal any hazardous leaks during normal operation
3.3
enhanced tightness
absence of leakage when due to the design and measures of maintenance any of the tightness tests or
tightness monitorings appropriate for the application does not reveal any hazardous leaks during
normal operations and expected malfunctions
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4 Risk assessment
4.1 General
This risk assessment shall be carried out for each individual situation in accordance with EN ISO 12100
and/or EN 15198, unless other standards can be identified as being more appropriate to the situation:
a) Identification of explosion hazards and determination of the likelihood of occurrence of a
hazardous explosive atmosphere (see 4.2);
b) Identification of ignition hazards and determination of the likelihood of occurrence of potential
ignition sources (see 4.3);
c) estimation of the possible effects of an explosion in case of ignition (see 4.4);
d) evaluation of the risk and whether the intended level of protection has been achieved;
NOTE The intended level of protection is defined by at least legal requirements and, if necessary, additional
requirements specified by the user.
e) consideration of measures to reduce of the risks (see Clause 6).
A comprehensive approach shall be taken, especially for complicated equipment, protective systems
and components, plants comprising individual units and, above all, for extended plants. This risk
assessment shall take into account the ignition and explosion hazard from:
1) the equipment, protective systems and components themselves;
2) the interaction between the equipment, protective systems and components and the substances
being handled;
3) the particular industrial process performed in the equipment, protective systems and components;
4) the surroundings of the equipment, protective systems and components and possible interaction
with neighbouring processes.
4.2 Identification of explosion hazards
4.2.1 General
The explosion hazard is generally related to the materials and substances processed, used or released
by equipment, protective systems and components and materials used to construct equipment,
protective systems and components. Some of these released substances can undergo combustion
processes in air. These processes are often accompanied by the release of considerable amounts of heat
and can be associated with a pressure build-up and the release of hazardous materials. In contrast to
burning in a fire, an explosion is essentially a self-sustained propagation of the reaction zone (flame)
through the explosive atmosphere. This potential hazard associated with explosive atmosphere is
released when ignited by an effective ignition source.
The safety characteristics listed in 4.2.2 and 4.2.3 describe safety relevant properties of flammable
substances. The material properties and the safety characteristics are used for the identification of the
explosion hazard.
It is necessary to bear in mind that such safety characteristics are not constants but depend for instance
on the techniques used for their measurement. Also, for dusts, tabulated safety data are for guidance
only because the values depend on particle size and shape, moisture content and the presence of
8
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additives even in trace concentrations. For a specific application, samples of the dust present in the
equipment should be tested and the data obtained used in the hazard identification.
4.2.2 Combustion properties
Since in this context it is not the material itself that represents the potential hazard but its contact or
mixing with air, the properties of the mixture of the flammable substance with air shall be determined.
These properties give information about a substance's burning behaviour and whether it could give rise
to fire or explosions. Relevant data are e.g.:
a) lower explosion point, substituted by flash point (see EN 15794);
b) explosion limits (LEL, UEL) (see EN 1839, EN 14034-3 and EN 1839);
c) limiting oxygen concentration (LOC) (see EN 14034-4 and EN 1839).
4.2.3 Explosion behaviour
The behaviour of the explosive atmosphere after ignition shall be characterized by data such as:
a) maximum explosion pressure (p ) (see EN 14034-1, EN 14034-4 and EN 15967);
max
b) maximum rate of explosion pressure rise ((d /d ) ), (see EN 14034-2, EN 14491 and EN 15967);
p t max
c) maximum experimental safe gap (MESG) (see EN 60079-1).
4.2.4 Likelihood of occurrence of a hazardous explosive atmosphere
The likelihood of occurrence of a hazardous explosive atmosphere depends on the following:
— presence of a flammable substance;
— degree of dispersion of the flammable substance (e.g. gases, vapours, mists, dusts);
— concentration of the flammable substance in air within the explosion range;
— amount of explosive atmosphere sufficient to cause injury or damage in case of ignition.
In assessment of the likelihood of occurrence of a hazardous explosive atmosphere, possible formation
of the explosive atmosphere through chemical reactions, pyrolysis and biological processes from the
materials present shall be taken into account.
If it is impossible to estimate the likelihood of occurrence of a hazardous explosive atmosphere, the
assumption shall be made that such an atmosphere is always present.
a) Presence of a flammable substance
Flammable and/or combustible substances shall be considered as materials which can form an
explosive atmosphere unless an investigation of their properties has shown that in mixtures with air
they are incapable of self-sustained propagation of an explosion. In assessment of the likelihood of
occurrence of a hazardous explosive atmosphere, possible formation of the explosive atmosphere
through chemical reactions, pyrolysis and biological processes from the materials present shall be taken
into account.
b) Degree of dispersion of flammable substances
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By their very nature, gases, vapours and mists have a degree of dispersion high enough to produce an
explosive atmosphere. For dusts the occurrence of an explosive atmosphere can be assumed if the
particle size fractions fall below 0,5 mm.
NOTE 1 Numerous mists, aerosols and types of dusts that occur in actual practice have particle sizes between
0,001 mm and 0,1 mm.
Attention shall be paid to the fact that explosions can occur in hybrid mixtures though none of the
flammable/combustible substances of the mixture is within the explosion range.
c) Concentration of flammable substances
An explosion is possible when the concentration of the dispersed flammable substance in air achieves a
minimum value (lower explosion limit). An explosion will not occur when the concentration exceeds a
maximum value (upper explosion limit).
NOTE 2 Some chemically unstable substances, e.g. acetylene and ethylene oxide, can undergo exothermic
reactions even in the absence of oxygen and have an upper explosion limit of 100 %.
The explosion limits vary with pressure and temperature. As a rule, the concentration range between
the explosion limits increases with increasing pressure and temperature. In the case of mixtures with
oxygen, the upper explosion limits are far higher than for mixtures with air.
If the surface temperature of a combustible liquid exceeds the lower explosion point, an explosive
atmosphere can be formed (see 6.2.1.2). Aerosols and m
...
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