Explosive atmospheres - Part 29-3: Gas detectors - Guidance on functional safety of fixed gas detection systems ( IEC 60079-29-3:2014)

EN IEC 60079-29-3 gives guidance for the design and implementation of a fixed gas detection system, including associated and/or peripheral gas detection equipment, for the detection of flammable gases/vapours and Oxygen when used in a safety-related application in accordance with IEC 61508 and IEC 61511. This International standard also applies to the detection of toxic gases. Other parts of this international standard and pertinent local, national and international standards separately specify the performance requirements of a gas detector and a gas detection control unit (logic solver). These standards are commonly known as Metrological Performance Standards and are concerned with the accuracy of the measured value, the overall system performance, but not the device or system integrity with respect to the safety function. This international standard applies to the integrity of the safety function. This international standard sets out safety-related considerations of fixed gas detection systems, including associated and/or peripheral gas detection equipment in terms of the framework and philosophy of IEC 61508, and introduces the particular requirements demanded by a fixed gas detection system as shown in Figure 2. This international standard does not consider the Safety Integrity Level SIL 4. SIL 4 is assumed to be unrealistic to be achieved for gas detection systems. This international standard is applicable for fixed gas detection systems, which might consist of the following hardware functional units - Gas sensor/transmitter - Gas detection control unit (logic solver) - Gas sampling (single and multiplexed streams) - Gas conditioning - Automatic gas calibration and adjustment - Output module (if not part of the control unit).

Explosionsfähige Atmosphäre - Teil 29-3: Gasmessgeräte - Leitfaden zur funktionalen Sicherheit von ortsfesten Gaswarnsystemen (IEC 60079-29-3:2014)

Atmosphères explosives - Partie 29-3: Détecteurs de gaz - Recommandations relatives à la sécurité fonctionnelle des systèmes fixes de détection de gaz (CIE 60079-29-3:2014)

L'IEC 60079-29-3:2014 donne des recommandations sur la conception et la mise en oeuvre d'un système fixe de détection de gaz, comprenant des équipements associés et/ou périphériques de détection de gaz, permettant de détecter des gaz/vapeurs inflammables et de l'oxygène dans le cadre d'une application relative à la sécurité conformément à l'IEC 61508 et à l'IEC 61511. La présente Norme internationale s'applique aussi à la détection des gaz toxiques. Les autres parties de la présente Norme internationale et les normes locales, nationales et internationales pertinentes spécifient séparément les exigences de performance d'un détecteur de gaz et d'une unité de commande de détection de gaz (unité logique). Ces normes sont généralement appelées Normes de Performances Métrologiques et traitent de la précision de la valeur mesurée, des performances globales du système, mais pas de l'intégrité du dispositif ou du système par rapport à la fonction de sécurité. La présente Norme internationale s'applique à l'intégrité de la fonction de sécurité. Mots clés: système fixe de détection de gaz, gaz/vapeurs inflammables et de l'oxygène, détection des gaz toxiques

Eksplozivne atmosfere - 29-3. del: Plinski detektorji - Navodilo o funkcijski varnosti fiksnih sistemov za odkrivanje plina (IEC 60079-29-3:2014)

Standard EN IEC 60079-29-3 zagotavlja smernice za načrtovanje in izvajanje fiksnih sistemov za odkrivanje plina, vključno z dodatno in/ali periferno opremo za odkrivanje plina, za odkrivanje vnetljivih plinov/hlapov in kisika pri uporabi v varnostnih pripravah v skladu s standardoma IEC 61508 in IEC 61511. Ta mednarodni standard se uporablja tudi za odkrivanje strupenih plinov. Drugi deli tega mednarodnega standarda in ustrezni lokalni, nacionalni in mednarodni standardi ločeno določajo zahteve glede zmogljivosti detektorja plina in nadzorne enote za odkrivanje plina (logic solver). Ti standardi so znani kot standardi meroslovnega delovanja ter obravnavajo točnost izmerjenih vrednosti in splošno delovanje sistema, ne pa celovite varnostne funkcije naprave ali sistema. Ta mednarodni standard se uporablja za integriteto varnostne funkcije. Ta mednarodni standard določa z varnostjo povezane dejavnike fiksnih sistemov za odkrivanje plina, vključno z dodatno in/ali periferno opremo za odkrivanje plina, z vidika ogrodja in filozofije standarda IEC 61508 in uvaja določene zahteve, ki jih zahteva sistem za odkrivanje plina na sliki 2. Ta mednarodni standard ne obravnava stopnje 4 integritete varnostnega sistema (SIL). Predpostavlja se, da integritete varnostnega sistema stopnje 4 pri sistemih za odkrivanje plina ni mogoče doseči. Ta mednarodni standard velja za fiksne sisteme za odkrivanje plina, ki jih lahko sestavljajo naslednje funkcijske enote strojne opreme: – senzor plina/oddajnik, – nadzorna enota za odkrivanje plina (logic solver), – vzorčenje plina (enojni tok in multipleksirani tokovi), – kondicioniranje plinov, – samodejna kalibracija in prilagajanje plinov, – izhodni modul (če ni del nadzorne enote).

General Information

Status
Published
Publication Date
20-Oct-2014
Current Stage
6060 - National Implementation/Publication (Adopted Project)
Start Date
27-Jun-2014
Due Date
01-Sep-2014
Completion Date
21-Oct-2014

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SLOVENSKI STANDARD
SIST EN 60079-29-3:2014
01-november-2014

Eksplozivne atmosfere - 29-3. del: Plinski detektorji - Navodilo o funkcijski varnosti

fiksnih sistemov za odkrivanje plina (IEC 60079-29-3:2014)

Explosive atmospheres - Part 29-3: Gas detectors - Guidance on functional safety of

fixed gas detection systems ( IEC 60079-29-3:2014)

Explosionsfähige Atmosphäre - Teil 29-3: Gasmessgeräte - Leitfaden zur funktionalen

Sicherheit von ortsfesten Gaswarnsystemen (IEC 60079-29-3:2014)

Atmosphères explosives - Partie 29-3: Détecteurs de gaz - Recommandations relatives à

la sécurité fonctionnelle des systèmes fixes de détection de gaz (CIE 60079-29-3:2014)

Ta slovenski standard je istoveten z: EN 60079-29-3:2014
ICS:
13.230 Varstvo pred eksplozijo Explosion protection
13.320 Alarmni in opozorilni sistemi Alarm and warning systems
29.260.20 (OHNWULþQLDSDUDWL]D Electrical apparatus for
HNVSOR]LYQDR]UDþMD explosive atmospheres
SIST EN 60079-29-3:2014 en

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

---------------------- Page: 1 ----------------------
SIST EN 60079-29-3:2014
---------------------- Page: 2 ----------------------
SIST EN 60079-29-3:2014
EUROPEAN STANDARD EN 60079-29-3
NORME EUROPÉENNE
EUROPÄISCHE NORM
June 2014
ICS 29.260.20
English Version
Explosive atmospheres - Part 29-3: Gas detectors - Guidance on
functional safety of fixed gas detection systems
(IEC 60079-29-3:2014)

Atmosphères explosives - Partie 29-3: Détecteurs de gaz - Explosionsfähige Atmosphäre - Teil 29-3: Gasmessgeräte -

Recommandations relatives à la sécurité fonctionnelle des Leitfaden zur funktionalen Sicherheit von ortsfesten

systèmes fixes de détection de gaz Gaswarnsystemen
(CEI 60079-29-3:2014) (IEC 60079-29-3:2014)

This European Standard was approved by CENELEC on 2014-05-01. CENELEC 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 CENELEC 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 CENELEC member into its own language and notified to the CEN-CENELEC Management Centre has the

same status as the official versions.

CENELEC members are the national electrotechnical committees of Austria, Belgium, Bulgaria, Croatia, Cyprus, the Czech Republic,

Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia,

Lithuania, Luxembourg, Malta, the Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland,

Turkey and the United Kingdom.
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung
CEN-CENELEC Management Centre: Avenue Marnix 17, B-1000 Brussels

© 2014 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELEC Members.

Ref. No. EN 60079-29-3:2014 E
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SIST EN 60079-29-3:2014
EN 60079-29-3:2014 - 2 -
Foreword

The text of document 31/1105A/FDIS, future edition 1 of IEC 60079-29-3, prepared by IEC TC 31,

Equipment for explosive atmospheres, was submitted to the IEC-CENELEC parallel vote and approved

by CENELEC as EN 60079-29-3:2014.
The following dates are fixed:
(dop) 2015-02-01
• latest date by which the document has
to be implemented at national level by
publication of an identical national
standard or by endorsement
• latest date by which the national (dow) 2017-05-01
standards conflicting with the
document have to be withdrawn

This part of IEC 60079-29 is to be used in conjunction with the following standards:

– IEC 60079-0, Explosive atmospheres – Part 0: Equipment – General requirements
– IEC 60079-29-1, Explosive atmospheres – Part 29-1: Gas detectors – Performance
requirements of detectors for flammable gases
– IEC 60079-29-2, Explosive atmospheres – Part 29-2: Gas detectors – Selection,
installation, use and maintenance of detectors for flammable gases and oxygen

– IEC 60079-29-4, Explosive atmospheres – Part 29-4: Gas detectors – Performance requirements of

open path detectors for flammable gases

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. CENELEC [and/or CEN] shall not be held responsible for identifying any or all such patent

rights.
Endorsement notice

The text of the International Standard IEC 60079-29-3:2014 was approved by CENELEC as a European

Standard without any modification.

In the official version, for Bibliography, the following notes have to be added for the standards indicated:

IEC 60079-1 NOTE Harmonised as EN 60079-10-1.
IEC 61511-1 NOTE Harmonised as EN 61511-1.
IEC 61511-2 NOTE Harmonised as EN 61511-2.
IEC 61511-3 NOTE Harmonised as EN 61511-3.
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SIST EN 60079-29-3:2014
- 3 - EN 60079-29-3:2014
Annex ZA
(normative)
Normative references to international publications
with their corresponding European publications

The following documents, in whole or in part, are normatively referenced in this document and are

indispensable for its application. For dated references, only the edition cited applies. For undated

references, the latest edition of the referenced document (including any amendments) applies.

NOTE 1 When an International Publication has been modified by common modifications, indicated by (mod), the relevant EN/HD

applies.

NOTE 2 Up-to-date information on the latest versions of the European Standards listed in this annex is available here:

www.cenelec.eu
Publication Year Title EN/HD Year
IEC 60079-29-1 - Explosive atmospheres -- Part 29-1: Gas EN 60079-29-1 -
(mod) detectors - Performance requirements of
detectors for flammable gases
+AA
IEC 60079-29-2 2007 Explosive atmospheres -- Part 29-2: Gas EN 60079-29-2 2007
detectors - Selection, installation, use and
maintenance of detectors for flammable
gases and oxygen
+EN 60079-29- 2007
2:2007/corrigendum
Dec. 2007
IEC 60079-29-4 - Explosive atmospheres -- Part 29-4: Gas EN 60079-29-4 -
(mod) detectors - Performance requirements of
open path detectors for flammable gases
+AA
IEC 61508 series Functional safety of EN 61508 series
electrical/electronic/programmable electronic
safety-related systems
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SIST EN 60079-29-3:2014
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SIST EN 60079-29-3:2014
IEC 60079-29-3
Edition 1.0 2014-03
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Explosive atmospheres –
Part 29-3: Gas detectors – Guidance on functional safety of fixed gas detection
systems
Atmosphères explosives –
Partie 29-3: Détecteurs de gaz – Recommandations relatives à la sécurité
fonctionnelle des systèmes fixes de détection de gaz
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
CODE PRIX X
ICS 29.260.20 ISBN 978-2-8322-1496-1

Warning! Make sure that you obtained this publication from an authorized distributor.

Attention! Veuillez vous assurer que vous avez obtenu cette publication via un distributeur agréé.

® Registered trademark of the International Electrotechnical Commission
Marque déposée de la Commission Electrotechnique Internationale
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SIST EN 60079-29-3:2014
– 2 – IEC 60079-29-3:2014 © IEC 2014
CONTENTS

FOREWORD ........................................................................................................................... 5

INTRODUCTION ..................................................................................................................... 7

1 Scope ............................................................................................................................ 10

2 Normative references .................................................................................................... 11

3 Terms and definitions .................................................................................................... 11

4 Requirements ................................................................................................................ 13

4.1 General ............................................................................................................ 13

4.2 Demand rate .................................................................................................... 13

5 Gas detection unique features ....................................................................................... 13

5.1 Objective ......................................................................................................... 13

5.2 Features .......................................................................................................... 14

5.2.1 General .......................................................................................... 14

5.2.2 Sensor location ............................................................................... 14

5.2.3 Sensor filter elements (passive) ...................................................... 14

5.2.4 Sensor filter elements (active) ........................................................ 14

5.2.5 Sensor principles ............................................................................ 14

5.2.6 Poisoning and adverse chemical reaction ....................................... 15

5.2.7 ppm.hr or %vol.hr lifetime ............................................................... 15

5.2.8 Negative gas readings .................................................................... 15

5.2.9 Hazard and risk analysis ................................................................. 15

5.2.10 Preventative effectiveness or mitigation effectiveness .................... 16

5.2.11 Cross sensitivities ........................................................................... 16

5.2.12 Special states ................................................................................. 16

5.2.13 Metrological performance standards ............................................... 16

5.2.14 Fault signal handling ....................................................................... 16

5.2.15 Over-range indication ..................................................................... 16

5.2.16 Surrogate calibration ...................................................................... 16

5.2.17 Maximum/minimum alarm set points ............................................... 17

6 Functional safety management ...................................................................................... 17

6.1 Objective ......................................................................................................... 17

6.2 Requirements .................................................................................................. 17

6.3 Competence .................................................................................................... 18

7 General requirements .................................................................................................... 19

7.1 Objective ......................................................................................................... 19

7.2 Requirements .................................................................................................. 19

7.2.1 General .......................................................................................... 19

7.2.2 Safety and non safety functions ...................................................... 19

7.2.3 Safety functions of different integrity targets ................................... 19

7.2.4 Behaviour under dangerous failure conditions................................. 19

7.2.5 Behaviour under safe failure conditions .......................................... 20

7.2.6 Behaviour under special state conditions ........................................ 20

7.2.7 Power supply .................................................................................. 21

7.2.8 Gas detector ................................................................................... 21

7.2.9 Gas detection control unit (logic solver) .......................................... 21

7.2.10 Final element (actuator) .................................................................. 22

7.2.11 Visual indication ............................................................................. 22

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SIST EN 60079-29-3:2014
IEC 60079-29-3:2014 © IEC 2014 – 3 –

7.2.12 Switching outputs ........................................................................... 22

7.2.13 Protocol outputs ............................................................................. 24

7.2.14 Protocol inputs ................................................................................ 24

7.2.15 System architecture, PFD and PFH values ..................................... 24

8 Gas detection unique requirements ............................................................................... 24

8.1 Objectives ........................................................................................................ 24

8.2 Requirements .................................................................................................. 25

8.2.1 Introduction to gas sampling ........................................................... 25

8.2.2 Gas sampling.................................................................................. 25

8.2.3 Gas multiplexer .............................................................................. 26

8.2.4 Gas multiplexer control system ....................................................... 27

8.2.5 Conditioning of measured gas ........................................................ 27

8.2.6 Gas sampling by diffusion mode ..................................................... 28

8.2.7 Automatic calibration and adjustment.............................................. 28

8.2.8 Automatic calibration and adjustment control system ...................... 29

9 Alternative control units (logic solvers) .......................................................................... 30

9.1 Objectives ........................................................................................................ 30

9.2 Requirements .................................................................................................. 30

9.2.1 Performance (metrological) ............................................................. 30

9.2.2 Programming of logic ...................................................................... 30

10 Factory acceptance testing ............................................................................................ 30

10.1 Objectives ........................................................................................................ 30

10.2 Requirements .................................................................................................. 30

10.2.1 Planning ......................................................................................... 30

10.2.2 Execution ....................................................................................... 31

11 Installation and commissioning ...................................................................................... 31

11.1 Objectives ........................................................................................................ 31

11.2 Requirements .................................................................................................. 32

11.2.1 Planning ......................................................................................... 32

11.2.2 Execution ....................................................................................... 32

12 System validation .......................................................................................................... 33

12.1 Objectives ........................................................................................................ 33

12.2 Requirements .................................................................................................. 33

12.2.1 Planning ......................................................................................... 33

12.2.2 Execution ....................................................................................... 33

13 Operation and maintenance ........................................................................................... 34

13.1 Objectives ........................................................................................................ 34

13.2 Requirements .................................................................................................. 34

13.2.1 Planning ......................................................................................... 34

13.2.2 Execution ....................................................................................... 34

14 System modification ...................................................................................................... 35

14.1 Objectives ........................................................................................................ 35

14.2 Requirements .................................................................................................. 35

14.2.1 Planning ......................................................................................... 35

14.2.2 Execution ....................................................................................... 35

15 System decommissioning .............................................................................................. 36

15.1 Objectives ........................................................................................................ 36

15.2 Requirements .................................................................................................. 36

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SIST EN 60079-29-3:2014
– 4 – IEC 60079-29-3:2014 © IEC 2014

15.2.1 Planning ......................................................................................... 36

15.2.2 Execution ....................................................................................... 36

16 Documentation .............................................................................................................. 37

16.1 Objectives ........................................................................................................ 37

16.2 Requirements .................................................................................................. 37

Annex A (informative) Typical Applications .......................................................................... 38

A.1 Typical diffusion applications ........................................................................... 39

A.1.1 Application 1 ................................................................................... 39

A.1.2 Application 2 ................................................................................... 40

A.1.3 Application 3 ................................................................................... 40

A.1.4 Application 4 ................................................................................... 40

A.2 Typical sampling applications ........................................................................... 41

A.2.1 Point to Point sampling ................................................................... 41

A.2.2 Multi-stream sampling ..................................................................... 42

Annex B (informative) Cross references between standards................................................. 43

Annex C (informative) Transformation of requirements ......................................................... 44

C.1 General ............................................................................................................ 44

C.2 SIL capability 1 ................................................................................................ 44

C.2.1 Characteristic ................................................................................. 44

C.2.2 Transformation ............................................................................... 44

C.3 SIL capability 2 ................................................................................................ 44

C.3.1 Characteristic ................................................................................. 44

C.3.2 Transformation ............................................................................... 45

C.4 SIL capability 3 ................................................................................................ 45

C.4.1 Characteristic ................................................................................. 45

C.4.2 Transformation ............................................................................... 45

Bibliography .......................................................................................................................... 46

Figure 1 – Gas Detection System Architecture ........................................................................ 8

Figure 2 − Related Safety Instrumented System Standards ................................................... 10

Figure A.1 – Gas detection safety loops ................................................................................ 39

Figure A.2 – Typical gas detector aspiration configurations ................................................... 41

Figure B.1 – Cross references between standards ................................................................ 43

Table 1 – Typical Job Descriptions and Most Relevant Clauses .............................................. 9

Table 2 – Demand for Functional Safety Management (see IEC 61508-1) ............................. 18

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SIST EN 60079-29-3:2014
IEC 60079-29-3:2014 © IEC 2014 – 5 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
EXPLOSIVE ATMOSPHERES –
Part 29-3: Gas detectors – Guidance on
functional safety of fixed gas detection systems
FOREWORD

1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising

all national electrotechnical committees (IEC National Committees). The object of IEC is to promote

international co-operation on all questions concerning standardization in the electrical and electronic fields. To

this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,

Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC

Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested

in the subject dealt with may participate in this preparatory work. International, governmental and non-

governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely

with the International Organization for Standardization (ISO) in accordance with conditions determined by

agreement between the two organizations.

2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international

consensus of opinion on the relevant subjects since each technical committee has representation from all

interested IEC National Committees.

3) IEC Publications have the form of recommendations for international use and are accepted by IEC National

Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC

Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any

misinterpretation by any end user.

4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications

transparently to the maximum extent possible in their national and regional publications. Any divergence

between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in

the latter.

5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity

assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any

services carried out by independent certification bodies.

6) All users should ensure that they have the latest edition of this publication.

7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and

members of its technical committees and IEC National Committees for any personal injury, property damage or

other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and

expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC

Publications.

8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is

indispensable for the correct application of this publication.

9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of

patent rights. IEC shall not be held responsible for identifying any or all such patent rights.

International Standard IEC 60079-29-3 has been prepared by IEC technical committee 31:

Equipment for explosive atmospheres.

This part of IEC 60079-29 is to be used in conjunction with the following standards:

– IEC 60079-0, Explosive atmospheres – Part 0: Equipment – General requirements
– IEC 60079-29-1, Explosive atmospheres – Part 29-1: Gas detectors – Performance
requirements of detectors for flammable gases
– IEC 60079-29-2, Explosive atmospheres – Part 29-2: Gas detectors – Selection,
installation, use and maintenance of detectors for flammable gases and oxygen
– IEC 60079-29-4, Explosive atmospheres – Part 29-4: Gas detectors – Performance
requirements of open path detectors for flammable gases
---------------------- Page: 11 ----------------------
SIST EN 60079-29-3:2014
– 6 – IEC 60079-29-3:2014 © IEC 2014
The text of this standard is based on the following documents:
FDIS Report on voting
31/1105A/FDIS 31/1117/RVD

Full information on the voting for the approval of this standard can be found in the report on

voting indicated in the above table.

This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.

A list of all parts of the IEC 60079 series, under the general title: Explosive atmospheres, can

be found on the IEC website.

The committee has decided that the contents of this publication will remain unchanged until

the stability date indicated on the IEC web site under "http://webstore.iec.ch" in the data

related to the specific publication. At this date, the publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.

IMPORTANT – The 'colour inside' logo on the cover page of this publication indicates

that it contains colours which are considered to be useful for the correct

understanding of its contents. Users should therefore print this document using a

colour printer.
---------------------- Page: 12 ----------------------
SIST EN 60079-29-3:2014
IEC 60079-29-3:2014 © IEC 2014 – 7 –
INTRODUCTION

Fixed gas detection systems have been used for many years to perform safety instrumented

functions. Like any instrumented system, a fixed gas detection system commonly comprises

of a single or multiple gas detector input(s), a control unit and a single or multiple final

element(s) or output(s). Additional peripheral equipment may be incorporated into a fixed gas

detection system e.g. a gas sampling system or a gas conditioning system. If a fixed gas

detection system, including any relevant peripheral equipment is to be effectively used for

safety instrumented functions, it is essential that the total system achieves certain minimum

standards and performance levels.

It is important to understand that the number of sensing points and their appropriate location,

their redundancy, the management of regular maintenance, specifically response checking or

calibration, and other gas detection specific features (such as design of gas sampling

systems) are all likely to have a far greater effect on the integrity of the overall Safety

Instrumented System (SIS) than the required Safety Integrity Level (SIL) or SIL-capability of

any of the individual functional units. This, however, does not exclude the requirement for

each Safety Instrumented Function (SIF) to have a stand-alone functional integrity.

This international standard addresses the minimum standards and performance levels of a

fixed gas detection system which is based on the use of electrical, electronic or

programmable electronic systems (E/E/PES) for any application where there is either a risk

reduction target stated o
...

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