ISO 22734
Hydrogen Generators Using Electrolysis Process


International Organization for Standardization (ISO)

Technical Committee No. 197 Hydrogen Technologies


ISO 22734
Hydrogen Generators Using Electrolysis Process


This document defines the construction, safety, and performance requirements of modular or factory-matched hydrogen gas generation appliances, herein referred to as hydrogen generators, using electrochemical reactions to electrolyze water to produce hydrogen.

This document is applicable to hydrogen generators that use the following types of ion transport medium: group of aqueous bases; group of aqueous acids; 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).

This document is applicable to hydrogen generators intended for industrial and commercial uses, and indoor and outdoor residential use in sheltered areas, such as carports, garages, utility rooms and similar areas of a residence.

Hydrogen generators that can also be used to generate electricity, such as reversible fuel cells, are excluded from the scope of this document.

Residential hydrogen generators that also supply oxygen as a product are excluded from the scope of this document.

The scope of the the revision of ISO 22734:2019 is to establish any additional safety requirements and test methods needed for:

i) operation of water electrolysis systems coupled with the electricity distribution grid and/or fluctuating

and intermittent renewable energy sources (RES) in a dynamic mode.

ii) safety requirements for venting of oxygen

iii) requirements for scale up including electrolyser systems installed into buildings

iv) other areas, such as

a. including learnings from other enclosed systems (e.g. HRS) and pre-normative research projects;

b. safety integrated systems;

c. power electronics for connection to the grid; and

d. specific requirements when incorporated into specific applications, e.g. as part of HRS, or hydrogen

grid injection system


Purpose and justification of the revision

The rapid expansion of renewable energy sources (RES) presents a challenge to balance the electric grid due to their intermittent nature - integration of electrolysis systems directly to RES or through the electrical grid in significant scale is anticipated to utilise hydrogen production to store excess energy and to stabilize the power grid.


These applications, with enlarged capacity per unit electrolysis technology, face a new challenge of performance and safety-related guidelines for their operation with fluctuating power input.


The performance of electrolyzer degrades with respect to a wide range of operating conditions: current density, temperature, pressure, shutdown frequency, etc. The degradation can occur at the material level (electrode and membrane) and/or at the system level (stack and BOP). It could affect flexibility (partial load/overload), dynamics, safety, and efficiency. Thus, the lack of test protocol for those process data can result in overestimation or suspicion of electrolyzer performance and can lead to safety issues.


The new standard should provide a specific guideline on a short-term or intermittent operation to define the flexibility and response for the electrolyzer coupled with RES directly in dynamic conditions. At the same time, the document will be developed to include additional guidance / requirements relating to scale-up of electrolyser systems, and oxygen venting, in addition to other aspects raised through either the NWIP ballot process, or to the working group once formed.


ISO 22734 was published in September 2019.

This edition combined ISO 22734-1:2008 (Industrial and Commercial Applications) and ISO 22734-2 (Residential Applications)


Revision initiated in June 2020.



 Nick Hart