Hydrogen (H₂) systems and ATEX: understanding the emerging safety gap

As hydrogen technologies spread rapidly across Europe, a critical regulatory and safety gap is drawing growing attention among specialists in IEC TC31, ISO TC197 and the EU ATEX working groups.

Modern hydrogen systems reach far beyond the original assumptions of the ATEX regulations - yet a hydrogen leak can still create an explosive atmosphere. That poses a complex compliance challenge which engineers, manufacturers and operators alike need to understand.

1) A simplified regulatory contradiction in hydrogen environments

The traditional ATEX framework was designed for industries such as:

• chemical plants
• oil refineries
• gas storage facilities
• pipeline systems

These environments typically operate at close to atmospheric pressure.

Modern hydrogen systems, however, differ substantially:

This divergence is the root of the current regulatory uncertainty.

2) Why does ATEX appear "not applicable"?

Directive 2014/34/EU applies only to equipment operating in a potentially explosive atmosphere under atmospheric conditions.

Atmospheric conditions are defined as:

• Pressure: 0.8–1.1 bar
• Temperature: −20 °C to +60 °C

Hydrogen systems, by contrast, typically:

• operate at 350–900 bar
• run in closed vessels and pipework

Conclusion:[Text Wrapping Break] Inside the system, ATEX does not apply. Compliance here falls under:

• the Machinery Regulation
• the Pressure Equipment Directive (PED)

3) The hydrogen leak paradox

The regulatory gap becomes clear the moment there is a leak:

• Hydrogen escapes at high pressure
• Rapid expansion follows
• The pressure drops to atmospheric level
• The hydrogen mixes with air

At that point the ATEX conditions are suddenly met:

• atmospheric pressure
• presence of a flammable mixture

This creates a legal and a safety transition between two regulatory regimes.

4) The Machinery Regulation - a clarification

Under EU Machinery Regulation 2023/1230, manufacturers must ensure:

• safe containment of hazardous substances
• the integrity of the system under pressure
• the prevention and management of leaks

Where a hazardous substance is present in the machine, safe operation is the manufacturer’s responsibility.

Inside the system:[Text Wrapping Break] ✔ Manufacturer’s responsibility[Text Wrapping Break] ✔ Pressure safety[Text Wrapping Break] ✔ Leak prevention[Text Wrapping Break] ✔ Mechanical integrity

5) When does ATEX become relevant again?

ATEX takes effect outside the equipment, where an explosive atmosphere may form.

Typical cases:

Operators must comply with Directive 1999/92/EC, including:

• classification of hazardous zones
• explosion protection documentation
• installation of suitable equipment

6) The role of Notified Bodies

Third-party certification is required where:

• the equipment operates in an explosive atmosphere
• the device falls into category 1 or 2
• special protective solutions are used

Typical hydrogen applications:

• compressors in Zone 2
• valves and sensors in a hazardous zone
• electrical systems exposed to hydrogen

7) A practical industrial approach

To manage the complexity, industry applies a clear division of responsibility:

8) Engineering strategy for hydrogen systems

1. Avoiding hazardous zones (the preferred solution)

Modern systems aim to eliminate ATEX zones through:

• ventilated enclosures
• outdoor installation
• hydrogen leak detection
• forced dilution

Goal: Zone 2 → non-hazardous area

Widely applied to:

• electrolysers
• hydrogen compressors
• fuel cell systems

2. Secondary explosion protection

Where zones cannot be avoided:

• use of ATEX certified (Ex) equipment
• control of ignition sources
• electrical and mechanical classification is mandatory

3. A layered safety concept

9) The real regulatory gap

The core problem:

• ATEX is built for atmospheric systems
• Hydrogen systems operate well above that

Industry is therefore moving towards an integrated safety approach:[Text Wrapping Break]functional safety combined with explosion protection

Key standards:

• ISO 19880 – hydrogen fuelling systems
• ISO 19880-1 – fuelling station safety
• IEC 60079-10-1 – zone classification
• IEC 60079-2 – pressurised systems

10) A practical industrial rule

A simple rule of thumb:

• Inside the system → Machinery Regulation + pressure safety
• Outside the system → ATEX

11) The key design principle

The safest approach is to prevent an explosive atmosphere from forming, rather than to manage one once it has.

This is consistent with the hierarchy set out in Directive 1999/92/EC.

12) A worked example: a hydrogen compressor skid (350 bar)

Doing it correctly:

• Manufacturer: ensure containment and machinery safety
• Operator: analyse leak risks and zones
• Equipment: ATEX certified

Conclusion

The rapid development of hydrogen technology exposes a real and significant regulatory gap between pressure-based systems and atmospheric explosion protection.

For safety and compliance:

• Manufacturers should focus on containment and system integrity
• Operators need to manage the explosion risks arising from a leak
• Engineers must develop an integrated safety concept

The future of hydrogen safety lies in combining prevention-focused design with intelligent explosion protection strategies.