SIST EN ISO 22734-1:2025

SLOVENSKI STANDARD
01-september-2025
Naprave za proizvodnjo vodika z elektrolizo vode - 1. del: Varnost (ISO 22734-
1:2025)
Hydrogen generators using water electrolysis - Part 1: Safety (ISO 22734-1:2025)
Wasserstofferzeuger auf Grundlage der Elektrolyse von Wasser - Teil 1:
Sicherheitsanforderungen (ISO 22734-1:2025)
Générateurs d'hydrogène utilisant le procédé d'électrolyse de l'eau - Partie 1: Sécurité
(ISO 22734-1:2025)
Ta slovenski standard je istoveten z: EN ISO 22734-1:2025
ICS:
71.100.20 Industrijski plini Gases for industrial
application
71.120.99 Druga oprema za kemijsko Other equipment for the
industrijo chemical industry
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD EN ISO 22734-1

NORME EUROPÉENNE
EUROPÄISCHE NORM
July 2025
ICS 71.100.20; 71.120.99
English version
Hydrogen generators using water electrolysis - Part 1:
Safety (ISO 22734-1:2025)
Générateurs d'hydrogène utilisant le procédé Wasserstofferzeuger auf Grundlage der Elektrolyse von
d'électrolyse de l'eau - Partie 1: Sécurité (ISO 22734- Wasser - Teil 1: Sicherheitsanforderungen (ISO 22734-
1:2025) 1:2025)
This European Standard was approved by CEN on 29 June 2025.

CEN and 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 CEN and 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 CEN and CENELEC member into its own language and notified to the CEN-CENELEC
Management Centre has the same status as the official versions.

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

CEN-CENELEC Management Centre:
Rue de la Science 23, B-1040 Brussels
© 2025 CEN/CENELEC All rights of exploitation in any form and by any means
Ref. No. EN ISO 22734-1:2025 E
reserved worldwide for CEN national Members and for
CENELEC Members.
Contents Page
European foreword . 3

European foreword
This document (EN ISO 22734-1:2025) has been prepared by Technical Committee ISO/TC 197
"Hydrogen technologies" in collaboration with Technical Committee CEN-CENELEC/ JTC 6 “Hydrogen in
energy systems” the secretariat of which is held by NEN.
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 January 2026, and conflicting national standards shall
be withdrawn at the latest by January 2026.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN-CENELEC shall not be held responsible for identifying any or all such patent rights.
Any feedback and questions on this document should be directed to the users’ national standards
body/national committee. A complete listing of these bodies can be found on the CEN and CENELEC
websites.
According to the CEN-CENELEC Internal Regulations, the national standards organizations of the
following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria,
Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland,
Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of
North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and the
United Kingdom.
Endorsement notice
The text of ISO 22734-1:2025 has been approved by CEN-CENELEC as EN ISO 22734-1:2025 without
any modification.
International
Standard
ISO 22734-1
First edition
Hydrogen generators using water
2025-07
electrolysis —
Part 1:
Safety
Générateurs d'hydrogène utilisant le procédé d'électrolyse
de l'eau —
Partie 1: Sécurité
Reference number
ISO 22734-1:2025(en) © ISO 2025

ISO 22734-1:2025(en)
© ISO 2025
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
or ISO’s member body in the country of the requester.
ISO copyright office
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CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii
ISO 22734-1:2025(en)
Contents Page
Foreword .vi
Introduction .vii
1 Scope . 1
1.1 General .1
1.2 Applicable hydrogen generators .1
1.3 Applicable ion transport mediums .1
1.4 Applicability to large scale hydrogen generators .1
1.5 Applicability to certain hydrogen generator subassemblies .2
1.6 Excluded hydrogen generators .2
2 Normative references . 2
3 Terms and definitions . 4
4 Requirements . 10
4.1 Operating conditions .10
4.1.1 Energy input specification .10
4.1.2 Feed water specifications .10
4.1.3 Ambient environment .11
4.1.4 Protective gas .11
4.1.5 Delivery of hydrogen. 12
4.1.6 Delivery of oxygen . . 12
4.1.7 Hydrogen venting . 12
4.1.8 Oxygen venting . 13
4.2 Risk management .14
4.2.1 General requirements .14
4.2.2 Fire and explosion hazard protection requirements .16
4.2.3 Pressure safety requirements .19
4.2.4 Temperature safety requirements . 20
4.2.5 Spillage, overflow, and drain . 20
4.2.6 Protection of service and maintenance personnel .21
4.3 Chemical reaction equipment .21
4.3.1 General .21
4.3.2 Electrochemical Cells and Stacks .21
4.3.3 Oxygen removal catalytic reactors . 22
4.3.4 Hydrogen removal catalytic reactors . 23
4.3.5 Gas drying systems . 23
4.4 Mechanical equipment . 23
4.4.1 General requirements . 23
4.4.2 General materials requirements .24
4.4.3 Pressure-bearing equipment . 25
4.4.4 Pressure relief devices .27
4.4.5 Fans and ventilators . 28
4.4.6 Heat transfer system . 28
4.5 Electrical equipment and wiring . 28
4.5.1 General requirements . 28
4.5.2 Grounding and bonding . . . 29
4.5.3 Touch current and protective conductor current . 29
4.5.4 Overcurrent protection . 29
4.5.5 Electric heaters . 29
4.5.6 Cord anchorage and conductor pull-out . 29
4.5.7 Power conversion equipment . 29
4.6 Control systems . 30
4.6.1 General . 30
4.6.2 Safety control circuit . 30
4.6.3 Control function in the event of failure .31
4.6.4 Programmable electronic equipment .31

iii
ISO 22734-1:2025(en)
4.6.5 Start .31
4.6.6 Emergency-stop .31
4.6.7 Stop .32
4.6.8 Self-correctable conditions .32
4.6.9 Interconnected installations .32
4.6.10 Safety components .32
4.6.11 Remote control systems .32
4.6.12 Alarms . 33
4.6.13 Protective gas quantity . 33
4.6.14 Reset . 33
4.6.15 Suspension of safeguards . 33
4.7 Enclosure requirements . 33
4.7.1 Minimum strength . 33
4.7.2 Ingress protection . 33
4.7.3 Fire resistance . 34
4.7.4 Thermal insulating materials . 34
4.7.5 Access openings . 34
4.7.6 Ventilation openings . 34
4.7.7 Containment of hazardous liquid leakage . 34
5 Test methods .35
5.1 General . 35
5.2 Type (qualification) tests . 35
5.2.1 General requirements . 35
5.2.2 Basic test arrangements . 35
5.2.3 Electrical tests .37
5.2.4 Pressure test . 38
5.2.5 Leakage test . 40
5.2.6 Dilution tests .41
5.2.7 Protection against the spread of fire tests .42
5.2.8 Temperature tests .42
5.2.9 Environmental test .42
5.2.10 Combustible gas mixture safety test .43
5.2.11 Spillage, overflow, and drain test .43
5.2.12 Stability test.43
5.2.13 Vent tests .43
5.2.14 Operational functional tests .45
5.2.15 Minimum generation rate test .45
5.3 Routine tests . . 46
5.3.1 General requirements . 46
5.3.2 Continuity of the protective bonding circuit test. 46
5.3.3 Voltage test . 46
5.3.4 Inspection of electrical equipment in hazardous areas . 46
5.3.5 Safety-control circuit functional tests . 46
5.3.6 Leakage test . 46
6 Marking and labelling .46
6.1 General requirements . 46
6.2 Hydrogen generator marking . 46
6.3 Marking of equipment .47
6.4 Warning labels . 48
7 Documentation .48
7.1 General . 48
7.2 Hydrogen generator ratings . 49
7.3 Hydrogen generator installation . 49
7.3.1 General . 49
7.3.2 Additional requirements for permanently connected hydrogen generators . 49
7.3.3 Additional requirements for indoor installations . 50
7.3.4 Additional requirements for built-in hydrogen generators . 50

iv
ISO 22734-1:2025(en)
7.3.5 Lifting . 50
7.4 Hydrogen generator operation . .51
7.5 Hydrogen generator maintenance .51
Annex A (informative) Hydrogen-assisted corrosion .53
Annex B (informative) Flammability limits of hydrogen .54
Annex C (informative) Reporting Crossover Of Hydrogen And Oxygen.55
Annex D (informative) Non-safety related performance tests .57
Bibliography .60

v
ISO 22734-1:2025(en)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out through
ISO technical committees. Each member body interested in a subject for which a technical committee
has been established has the right to be represented on that committee. International organizations,
governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely
with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are described
in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types
of ISO document should be noted. This document was drafted in accordance with the editorial rules of the
ISO/IEC Directives, Part 2 (see www.iso.org/directives).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions
related to conformity assessment, as well as information about ISO's adherence to the World Trade
Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 197, Hydrogen technologies, in collaboration
with the European Committee for Standardization (CEN) Technical Committee CEN/CLC/JTC 6, Hydrogen in
energy systems, in accordance with the Agreement on technical cooperation between ISO and CEN (Vienna
Agreement).
This first edition of ISO 22734-1 cancels and replaces ISO 22734:2019.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.

vi
ISO 22734-1:2025(en)
Introduction
The electrochemical cells of a hydrogen generator system dissociate water molecules (H O) into two
hydrogen (H ) gas molecules and one oxygen (O ) gas molecule when direct electrical current (e-) is applied.
2 2
H gas forms at the negative (-) cathode electrode and O gas forms at the positive (+) anode electrode. An
2 2
ion transport medium between the electrodes, a solid electrolyte membrane or a liquid electrolyte held in a
microporous diaphragm, additionally functions to keep product H and O gases separate.
2 2
Water electrolysis hydrogen generator systems include the cell(s), electrical conditioning, gas processing,
feed water, electrolyte management, cooling, ventilation, and control equipment. Gas compression, feed
water conditioning, and other auxiliary equipment can be included. These systems can scale from small self-
contained appliances to a group of factory-matched modules comprising large plant size installations.
This document is intended to assess water electrolysis hydrogen generator safety and may be used for
certification purposes.
NOTE See ISO/IEC 17000 for further guidance on certification.

vii
International Standard ISO 22734-1:2025(en)
Hydrogen generators using water electrolysis —
Part 1:
Safety
1 Scope
1.1 General
This document specifies the safety requirements of hydrogen gas generation appliances or systems that
use electrochemical reactions to electrolyse water to produce hydrogen, herein referred to as hydrogen
generators.
1.2 Applicable hydrogen generators
This document is applicable to:
— hydrogen generator appliances or systems (containerised, or skid mounted, complete hydrogen
generation systems);
— factory-matched modules (supplied by the same manufacturer) that, when connected together, form a
complete hydrogen generation system;
— hydrogen generators intended for industrial, commercial and residential applications;
— hydrogen generators intended for indoor or outdoor environments.
NOTE When this document is applied to hydrogen gas generation appliances or systems intended for installation
into buildings, additional requirements for the design of the building are likely to apply. These building requirements
are not addressed in this document. Additionally, the hydrogen generator enclosure requirements in this document do
not necessarily translate to requirements for a building.
Guidance for hydrogen generators that also provide oxygen used for industrial and commercial applications
is provided in this document, however additional considerations can apply.
1.3 Applicable ion transport mediums
This document is applicable to hydrogen generators that use the following types of ion transport medium:
— aqueous alkaline (basic) electrolytes, such as solutions of potassium hydroxide or sodium hydroxide;
— aqueous acidic electrolytes, such as dilute sulphuric acid;
— solid polymeric materials with acidic function group additions, such as acid proton exchange
membrane (PEM);
— solid polymeric materials with basic function group additions, such as anion exchange membrane (AEM).
1.4 Applicability to large scale hydrogen generators
This document is applicable to large scale hydrogen generators assembled on site.
NOTE 1 Large scale water electrolysis systems typically have a production rate of 100 kg/hour or more and can be
assembled using modules or equipment from various manufacturers.

ISO 22734-1:2025(en)
NOTE 2 Building requirements are not addressed in this document and the hydrogen generator enclosure
requirements in this document do not necessarily translate to requirements for a building.
1.5 Applicability to certain hydrogen generator subassemblies
This document is applicable to:
— electrochemical cell stacks (as stand-alone products);
— modules (sub-systems) for integration into larger hydrogen generation systems.
In such cases, the entirety of this document will not be applicable, and the specific sections relevant to the
product are established in order to develop a product conformance strategy.
1.6 Excluded hydrogen generators
This document is not applicable to the following:
— residential hydrogen generators that also supply oxygen as a product;
— hydrogen generators that can also be used to generate electricity, such as reversible fuel cells (refer to
IEC 62282-8-101, IEC 62282-8-102 and IEC 62282-8-201);
— hydrogen generators that use solid oxide electrolyte (refer to IEC 62282-8-101 and IEC 62282-8-201).
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes
requirements of this document. For dated references, only the edition cited applies. For undated references,
the latest edition of the referenced document (including any amendments) applies.
ISO 3864-2, Graphical symbols — Safety colours and safety signs — Part 2: Design principles for product safety labels
ISO 4126-1, Safety devices for protection against excessive pressure — Part 1: Safety valves
ISO 4126-2, Safety devices for protection against excessive pressure — Part 2: Bursting disc safety devices
ISO 4126-6, Safety devices for protection against excessive pressure — Part 6: Application, selection and
installation of bursting disc safety devices
ISO 4126-9, Safety devices for protection against excessive pressure — Part 9: Application and installation of
safety devices excluding stand-alone bursting disc safety devices
ISO 4126-10, Safety devices for protection against excessive pressure — Part 10: Sizing of safety valves and
bursting discs for gas/liquid two-phase flow
ISO 7010, Graphical symbols — Safety colours and safety signs — Registered safety signs
ISO 7866, Gas cylinders — Refillable seamless aluminium alloy gas cylinders — Design, construction and testing
ISO 9809-1, Gas cylinders — Design, construction and testing of refillable seamless steel gas cylinders and tubes
— Part 1: Quenched and tempered steel cylinders and tubes with tensile strength less than 1 100 MPa
ISO 10286, Gas cylinders — Terminology
ISO 11119-1, Gas cylinders — Design, construction and testing of refillable composite gas cylinders and tubes —
Part 1: Hoop wrapped fibre reinforced composite gas cylinders and tubes up to 450 l
ISO 11119-2, Gas cylinders — Design, construction and testing of refillable composite gas cylinders and tubes —
Part 2: Fully wrapped fibre reinforced composite gas cylinders and tubes up to 450 l with load-sharing metal liners

ISO 22734-1:2025(en)
ISO 11119-3, Gas cylinders — Design, construction and testing of refillable composite gas cylinders and tubes
— Part 3: Fully wrapped fibre reinforced composite gas cylinders and tubes up to 450 l with non-load-sharing
metallic or non-metallic liners or without liners
ISO 12100, Safety of machinery — General principles for design — Risk assessment and risk reduction
ISO 13850, Safety of machinery — Emergency stop function — Principles for design
ISO 15534-1, Ergonomic design for the safety of machinery — Part 1: Principles for determining the dimensions
required for openings for whole-body access into machinery
ISO 15534-2, Ergonomic design for the safety of machinery — Part 2: Principles for determining the dimensions
required for access openings
ISO 15534-3, Ergonomic design for the safety of machinery — Part 3: Anthropometric data
ISO 16111, Transportable gas storage devices — Hydrogen absorbed in reversible metal hydride
ISO 16528-1, Boilers and pressure vessels — Part 1: Performance requirements
ISO 17398, Safety colours and safety signs — Classification, performance and durability of safety signs
ISO 20485, Non-destructive testing — Leak testing — Tracer gas method
ISO 26142, Hydrogen detection apparatus — Stationary applications
ISO 80079-36, Explosive atmospheres — Part 36: Non-electrical equipment for explosive atmospheres — Basic
method and requirements
ISO 80079-37, Explosive atmospheres — Part 37: Non-electrical equipment for explosive atmospheres — Non-
electrical type of protection constructional safety ''c'', control of ignition sources ''b'', liquid immersion ''k''
IEC 31010:2019, Risk management — Risk assessment techniques
IEC 60068-2-18:2017, Environmental testing — Part 2-18: Tests — Test R and guidance: Water
IEC 60079-0, Explosive atmospheres – Part 0: Equipment. General requirements
IEC 60079-10-1, Explosive atmospheres – Part 10-1: Classification of areas. Explosive gas atmospheres
IEC 60079-14, Explosive atmospheres - Part 14: Electrical installations design, selection and erection
IEC 60079-17, Explosive atmospheres - Part 17: Electrical installations inspection and maintenance
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/IEEE 60079-30-1, Explosive atmospheres - Part 30-1: Electrical resistance trace heating - General and
testing requirements
IEC 60204-1, Safety of machinery — Electrical equipment of machines — Part 1: General requirements
IEC 60335-1:2020, Household and similar electrical appliances — Safety — Part 1: General requirements
IEC 60445, Basic and safety principles for man-machine interface, marking and identification — Identification
of equipment terminals, conductor terminations and conductors
IEC 60529, Degrees of protection provided by enclosures (IP Codes)
IEC 60730-1:2022, Automatic electrical controls — Part 1: General requirements
IEC 60947-1, Low-voltage switchgear and controlgear — Part 1: General rules

ISO 22734-1:2025(en)
IEC 60998-2-2, Connecting devices for low-voltage circuits for household and similar purposes — Part 2-2:
Particular requirements for connecting devices as separate entities with screwless-type clamping units
IEC 60999-1, Connecting devices — Electrical copper conductors — Safety requirements for screw-type and
screwless-type clamping units — Part 1: General requirements and particular requirements for clamping units
for conductors from 0,2 mm2 up to 35 mm2 (included)
IEC 60999-2, Connecting devices — Electrical copper conductors — Safety requirements for screw-type and
screwless-type clamping units — Part 2: Particular requirements for clamping units for conductors above
35 mm2 up to 300 mm2 (included)
IEC 61010-1:2010/AMD1:2016, Safety requirements for electrical equipment for measurement, control, and
laboratory use — Part 1: General requirements
IEC 61131-1, Programmable controllers — Part 1: General information
IEC 61131-2, Programmable controllers — Part 2: Equipment requirements and tests
IEC 61508, Functional safety of electrical/electronic/programmable electronic safety-related systems
IEC 62368-1, Audio/video, information and communication technology equipment — Part 1: Safety requirements
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
cell separator
material that provides gas separation between the anode and cathode, either a membrane (3.27) or a
diaphragm (3.7)
3.2
certification
third-party attestation related to products, processes, systems, or persons
[SOURCE: IEC 60050: 902-04-05, modified — removed Notes to entry 1 and 2.]
3.3
clean air
air that is essentially free of combustible dust, and contains no more than trace amounts of flammable
vapour or gas
[SOURCE: IEC 60079-13:2017, 3.3.]
3.4
commercial
use of hydrogen generators by laypersons in non-manufacturing business facilities, such as stores, hotels,
office buildings, educational institutes, filling stations, warehouses, and other non-residential locations
3.5
containment system
part of the equipment containing a flammable substance that may constitute a source of release
[SOURCE: IEC 60050: IEV 426-09-06, modified — removed “an internal” before “source of release”.]
...