CH35: New 2025 Version – Exclusive Review
Introduction
CH35 is one of the most important articles in the safety regulations against fire and panic risks in establishments receiving the public (ERP). It sets the conditions for using refrigerants (flammable and toxic) in thermodynamic systems such as air conditioning, air conditioning, heating, and domestic hot water production.
After several modifications over the years, a new version of CH35 came into force on September 1, 2025, replacing the old version from the order of June 25, 1980 (modified in 2019). This update clarifies, strengthens, and modernizes the regulations, notably incorporating technological developments and European standards (particularly the EN 378 standard).
In this article, we will decode the main differences between the old and new versions of CH35, and explain what this concretely changes for installers, operators, and project owners.
1. Expanded and Precise Definitions
The first notable difference lies in the definitions.
Old version (2019): defined only two terms:
- Flammable refrigerants: flame propagation at 60°C and 101.3 kPa.
- Toxic refrigerants: proven toxicity at less than 400 ppm.
New version (2025): significantly enriches this lexical field with:
- A definition of the thermodynamic system (complete circuit with piping, units, equipment).
- A definition of the machinery room, considered as an enclosed and isolated space.
- A clarification on open-air space, which is not considered as a room within the meaning of the regulations.
This precision of terms in the new CH35 helps avoid gray areas and facilitates the application of the text by operators and installers.
2. Evolution of Machinery Room Rules
Machinery rooms are at the heart of the safety system.
Old text:
- Room classified as a medium-risk room.
- Requirement of 2 ventilation openings to the outside.
- Strict separation from the boiler room.
New text:
- Room now classified as a standard-risk room by default.
- But if flammable (above the critical threshold) or toxic refrigerants are present:
- Mechanical ventilation required.
- Reinforced isolation (compliance with article CO 28 §2).
- Prohibition of direct communication with rooms accessible to the public.
The new version of CH35 therefore better distinguishes standard cases from at-risk cases, which relaxes certain constraints while strengthening safety in case of proven danger.
3. Piping and Connections: More Flexibility
The rules regarding piping are also evolving.
Old text:
- Metal piping mandatory.
- Prohibition of demountable fittings for flammable refrigerants (except at unit level).
New text:
- Piping still metal, but brazed or welded.
- Authorization of demountable and non-demountable fittings for units.
Here, the new version of CH35 offers greater installation flexibility, adapted to modern practices, while guaranteeing mechanical resistance and better safety against sudden ruptures.
4. Exclusion Zones: A Modernized Calculation
The exclusion zone corresponds to the space around fittings where any ignition source is prohibited.
Old text:
- Radius determined solely according to piping diameter and lower flammability limit (LFL).
New text:
- Introduction of a more detailed table taking into account several parameters:
- diameter,
- molar mass,
- pressure,
- LFL.
- Exemption of electrical equipment specific to units in this zone.
The new CH35 adopts a more scientific and precise approach, in line with developments in modern refrigerants.
5. Maximum Refrigerant Charge
The limitation of refrigerant charge aims to avoid reaching the flammability limit in case of leakage.
Old text:
- Charge calculated via a standard formula (mmax).
- Possible exceptions if detectors + ventilation present in machinery room.
New text:
- Same calculation formula, but clear distinctions according to location:
- Machinery rooms: no limit if detection + ventilation comply with EN 378 standard.
- Other rooms: no limit if early detection device and airtight closure system with forced mixing are present.
The explicit reference to the EN 378 standard in the new CH35 strengthens consistency with European standards.
6. Conditions for the Use of Toxic Fluids
Old version:
- Installation only in machinery room or outside.
- Operation in indirect exchange.
- Charge limited to 150 kg.
New version:
- These conditions resumed + obligation of mechanical protection of piping (≥ 2 m height or protection device).
The new version of CH35 therefore imposes additional safety against risks related to toxic fluids.
7. Controls and Verifications
Old text:
- Annual verification by a technician.
- Test of 20% of devices each year → 100% tested in 5 years.
New text:
- Mandatory leak tightness control with report.
- Full verification of all devices every 3 years.
The new CH35 simplifies periodicity (clearer) but imposes a global verification, guaranteeing better reliability over time.
8. Impacts for the Stakeholders
For Installers
- More freedom in the choice of fittings and assembly methods.
- Obligation to respect new zoning rules and safety distances.
For Operators
- Maximum charges managed more flexibly, especially with the support of detection systems.
- Fewer annual checks, but more demanding every 3 years.
For Control Bodies
- Installation verification now harmonized with EN 378 standard.
- Greater importance of technical documents provided (plans, schematics, calculations).
9. How to Comply with the New Version of CH35?
- Check room classification: machinery room, open-air space, areas accessible to the public.
- Update technical documentation: schematics, piping plans, safety devices.
- Check compliance of fittings and piping: brazing, welding, mechanical protection.
- Install detection devices adapted to the fluids used.
- Plan a global check every 3 years, integrating leak tightness monitoring.
Conclusion
The new version of CH35, which came into force in September 2025, marks an important step in the modernization of fire regulations for ERPs. It introduces clearer definitions, relaxes certain constraints (machinery rooms, fittings), while strengthening safety requirements (exclusion zones, toxic fluids, periodic controls).
By integrating the EN 378 standard, CH35 aligns with European standards and offers operators and installers a framework that is both more precise and more pragmatic.
The watchword of this new regulation: flexibility and reinforced safety.
Operators must now adapt their installations and procedures to remain compliant, and anticipate upcoming controls.
Additional Resources
- Journal officiel de la République française – N° 209 du 9 septembre 2025 (PDF)
- Site web DCRR
- LinkedIn – Tony Ciatti
Source: L’équipe DCRR