ISO 22734-1: Important safety-related changes in the 2025 version of the standard, compared with the 2019 version

Standard ISO 22734-1:2025 "Hydrogen generators using water electrolysis", Part 1: Safety

The standard ISO 22734 specifies requirements for hydrogen generators or electrolysers that use electrochemical reactions to break down water into hydrogen and oxygen. It is relevant for industrial, commercial and domestic applications and supports the safe and sustainable use of hydrogen as an energy carrier.

The revised 2025 version of the standard introduces significant innovations and enhancements directed at a more holistic approach to safety and technical progress in hydrogen technology. It is aimed at developers, operators and safety officers in industrial and commercial applications. The most important safety-related changes compared to the 2019 version are listed below:

1. Structure of the safety requirements

The safety requirements have moved from a control technology focus (Clause 4.5 in 2019) to a comprehensive risk management approach (Clause 4.2 in 2025). New considerations include:

• Residual voltage and residual charge in components
• Oxygen flow rate
• Excess water in hydrogen or oxygen pipes

2. Gas Crossover

For the first time, the standard addresses the risks posed by hydrogen-oxygen crossover, which can lead to the formation of explosive mixtures. New requirements include:

• Monitoring the pressure difference between the H₂ and O₂ sides in the cell stack
• Definition of minimum operating parameters (current, temperature, pressure)
• Technical guidelines in the new Annex C

3. Functional Safety

More choice when applying functional safety standards:

• IEC 61508 and IEC 61511 (as before)
• New: IEC 62061 and ISO 13849. This allows a more precise customisation to different industrial safety concepts

4. Cybersecurity

With the 2025 version, cybersecurity becomes mandatory for the first time:

• Remote-controllable systems must be ISO/IEC 27001-compliant
• Manufacturers must implement protective measures against unauthorised access and vulnerabilities over the whole lifecycle

Conclusion:

ISO 22734-1:2025 represents an important step towards holistic safety and system integrity. It provides clear technical guidelines for the development and operation of modern electrolysers - and strengthens the foundation for a safe hydrogen economy.

• Functional Safety and Industrial Security
• Applications in the hydrogen industry
• International Standards Organisation - ISO 22734