Standards
Safety standards: from inhibitor to enabler of natural refrigerants
For three decades, the rules that define a “safe” refrigeration system have decided how far natural refrigerants could go. Daniel Colbourne, who is active on several IEC, ISO and CEN standardisation committees explains how the core safety standards are changing, what still holds hydrocarbons back and why the revision of EN 378 matters now.
Dr Daniel Colbourne, Re-phridge Ltd
Every refrigeration, air-conditioning and heat pump (RACHP) system is built to a safety standard. As expectations of safety have risen, RACHP safety standards have become increasingly important. They prescribe requirements for achieving a “safe” system: for instance, how much refrigerant may be charged, where a system may be installed, what detection and ventilation must be in place. They are written by technical committees comprising manufacturers, users, test laboratories and other stakeholders and can exert a lot of influence on refrigerant selection decisions. Since the advent of the Montreal Protocol, national and international standards have received more and more attention, as in principle, they should facilitate the implementation of alternative refrigerants with tolerable impact on risk.
Natural refrigerants have been treated differently. As the use of R717 (ammonia) has been consistent for over a century in industrial and process applications, safety standards have been consistent and practical. Due to the relatively benign nature of R744 (carbon dioxide) with lower toxicity and non-flammability, it has never been seriously constrained by the standards. For Hydrocarbons (HCs), though, such as R600a (isobutane) and R290 (propane), inclusion of reasonable requirements into the standards has been a struggle over the past few decades. This has been partly due to lack of constructive data, concerns of stakeholders and practitioners and partly resistance from those businesses that would be affected by wide introduction of such fluids.
The “core” RACHP safety standards include:
EN IEC 60335-2-40 covering a wide range of AC and HP appliances
EN IEC 60335-2-89 for commercial refrigeration appliances
EN 378 is a European standard which deals with all RACHP systems
ISO 5149 is an international standard, similarly for all types of systems
What has changed: Over the past 10 – 15 years, requirements in safety standards have been greatly improved and various standards development committees are evolving to bring better and more practical requirements into these standards, rather than blanket restrictions that effectively blocked the introduction of certain refrigerants across a range of different systems and applications. With the exponential increase of interest in natural refrigerants, largely driven by European activities, but also being strongly encouraged by international events such as the Kigali Amendment to the Montreal Protocol, more stakeholders are paying attention to the rules laid out in these safety standards.
Two milestones stand out enabling much wider application of natural refrigerants. In June 2019 IEC 60335-2-89 raised the permitted charge of A3 (higher-flammability) refrigerants in self-contained commercial refrigeration appliances from 150 g to 500 g. For the first time, a full-size R290 display cabinet in a supermarket became possible under this international standard. In April 2022, after a six-and-a-half-year revision, publication of Edition 7 of IEC 60335-2-40 included requirements that drastically reduced the minimum room sizes for systems using up to 1 kg of HCs, thus removing a significant barrier to their use.
“A large system charge does not have to mean a large release.”
Dr Daniel Colbourne, Re-phridge Ltd
EN 378, being a standard that most designers, planners and operators work with day to day, is currently going through a similar process. The draft standard currently includes increased charge limits, a range of options for enabling greater refrigerant quantities for a room of a given size, introduction of the releasable charge approach and more refined ventilation methodologies. The draft revision, prEN 378:2025, was in public enquiry from July to September 2025 and the final vote is expected in 2027, with publication following, if the vote is positive. A new edition of ISO 5149, its international counterpart, is being published but unfortunately retains the majority of its established obstructive requirements, such as restrictive charge limits and refrigerant quantity calculations, sustaining significant barriers to the adoption of HCs across a wider range of systems and applications.
Specifically, certain areas will decide how quickly the next editions keep pace with what is technically possible:
Leak detection and response: technologies for leak detection and initiation of mitigation measures are progressing rapidly, with new developments being frequently reported. These are not well handled in the safety standards so future editions are expected to handle requirements for these in a more practicable manner.
Upper charge /cap quantity limits: standards currently impose limits on the refrigerant charge of a system, often reflecting historical concerns rather than from risk data. As confidence and understanding of the risk-related mechanisms improve throughout the industry, and demand grows for larger systems using natural refrigerants, these restrictions are being dissolved.
Releasable charge: a large system charge does not have to mean a large release. As with charge limits, there is increasing recognition of technologies which shut-off sections of a system so as to minimise the size of releases, despite a large system charge. Formalised approaches are gradually finding their way into the standards.
Standards work is slow, technical and rarely visible from the outside, yet they have a strong influence on the transition to natural refrigerants. But the importance of safety standards is increasingly recognised and similarly the need for constructive improvements. Moreover, once a standard is well written and refined, it can be an effective enabler for deployment of safe, cost-effective RACHP systems with natural refrigerants, giving confidence to those who are new to the sector. Thirty years on, some eurammon members already contribute to RACHP safety standards committees and growing interest is expected to encourage wider participation. The more the sector takes part, with design expertise, operating data, field experience and test data, the faster the standards will reflect what practitioners already know: that natural refrigerants can be applied safely across the full range of RACHP applications.
Part of our anniversary publication “30 Years of Championing Refrigerants by Nature”.
