20 June 2025
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Tim Mitchell, Sales Director at Klima Therm explores the challenges and benefits associated with natural refrigerants, dismantling some of the fear factors that have limited adoption of these high-performing, futureproof heat pump options.
Natural refrigerants – those existing in or derived from nature – have a long history that predates the synthetic, man-made alternatives that were commonly used throughout the 20th century. In the mid1800s, ethyl ether was used in the first mechanical vapor-compression refrigeration systems, including early designs by inventors like Jacob Perkins, who built one of the first such machines in 1834. However, while early natural refrigerants produced effective cooling, the safety risks – particularly flammability – eventually led to the development of safer natural refrigerants like ammonia, and later by synthetic refrigerants, including chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs), and hydrofluorocarbons (HFCs). It wasn’t until 1973 that scientists first raised concerns about the impact of CFCs on the ozone layer, a discovery that triggered decades of research, eventually leading to the phasing out of ozonedepleting substances. With European F-Gas regulations aiming to end the use of HFCs by 2050, the tables have now turned back in favour of natural refrigerants.
Back to basics
Natural refrigerants, such as CO2 (R744), propane (R290) and ammonia (R717), are recognised for their ultralow Global Warming Potential (GWP), zero ozone depletion potential and efficient performance in the heating and cooling industry. Each has its strengths and challenges:
• Ammonia excels in large-scale applications like district heating and cooling, and industrial processes. Its thermodynamic efficiency is hard to beat, but it must be handled with care due to toxicity at higher concentrations and mild flammability.
• Hydrocarbons, including propane, are highly efficient and widely available. They have extremely low global warming potential (GWP) and zero ozone depletion potential (ODP), but due to their high flammability, strict safety protocols are required for their use.
• Carbon Dioxide (CO2 ), once sidelined by synthetic refrigerants, is now enjoying a resurgence. It is nontoxic, non-flammable, and (being the baseline of all GWPs) has a GWP of 1 – making it an attractive choice for future-proof cooling and heating applications. It does. However, operate at very high pressures and has some slightly limiting characteristics in HVAC temperature ranges.
Yet despite the obvious sustainability benefits, some in the industry remain hesitant due to safety concerns which in my experience, rarely stand up to real-world evidence.
Myth 1 - Natural refrigerants are too dangerous to be used safely in commercial buildings While some natural refrigerants pose safety risks, these are well understood and can be effectively managed through smart system design and engineering controls. Propane, for instance, is an A3-class refrigerant — non-toxic but highly flammable — yet it delivers high performance heating and cooling commercial settings. By incorporating built-in safety measures such as integrated leak detection, mechanical ventilation and limiting the refrigerant charge to below 5kg, the risks can be minimised to acceptable levels. With proper design, installation, and maintenance, natural refrigerants can be safe, efficient, and fully compliant with safety standards. Over the last 15 years, we’ve installed more than 300 propanebased heat pump systems across the UK and Europe and there has never been a single incident where the refrigerant has posed any danger. These results are no fluke – they stem from wellestablished safety protocols, precision engineering and specialist training. When handled correctly, propane is just as safe as many synthetic refrigerants. Conversely, CO2 is non-toxic, non-flammable and non-corrosive, making it a safe and environmentally friendly refrigerant. It’s also physically stable and forms part of the natural carbon cycle, making it safer and more sustainable than often perceived. It does, however, operate at high pressures - up to 90 bar or so in some HVAC systems – and the machines therefore tend to be more robustly designed to ensure safety overall. Specialist training is required to safely handle, service, maintain and install these systems – again an easily surmountable challenge. Ammonia is toxic and corrosive, but its use in commercial refrigeration is well-established and safety concerns surrounding leaks or releases can be mitigated with proper ventilation and strict safety protocols. Ammonia is also less expensive than synthetic refrigerants and ammonia HVAC systems are generally more efficient than their synthetic alternative systems.
Myth 2 - Natural refrigerants are outdated and less efficient than synthetic alternatives The idea that natural refrigerants are outdated is rooted in their long history, which began before synthetic alternatives, like CFCs and HFCs, were developed. It can often seem like a backwards step to return to something that was discovered hundreds of years ago, especially when modern innovations have outpaced it. However, this idea of evaluating older, simpler technologies that were sidelined during the industrial revolution – not because they failed but because modern ‘innovations’ were more commercially appealing at the time. An example of this is electric vehicles (EVs) which were first developed in the late 1800s but were soon overtaken by internal combustion engines. Now, with focus on decarbonisation, EVs have come full circle – supported by modern technology, they are a leading solution for low-emission transport. Similarly, natural refrigerants are being rediscovered and refined together with new technological advancements to meet modern efficiency and environmental standards. The advanced commercial heat pump systems available today are designed to maximise the thermodynamic properties of natural refrigerants to deliver high-temperature, highperformance heating – up to 95°C in some cases, while working efficiently in extreme conditions, including down to -20°C. Natural refrigerants also tend to achieve higher Coefficients of Performance (CoPs) than their synthetic counterparts, particularly in high-temperature or variable-load scenarios. This results in lower energy consumption, reduced operational costs and a smaller carbon footprint over the life of the system. With continual advancements in control systems, component design and safety engineering, natural refrigerants are not only as efficient as synthetic alternatives, in many cases they are more efficient, more sustainable and more future-proof.
Myth 3 - Natural refrigerants are complex and impractical Natural refrigerants may require some specialist training and different design considerations, but ‘complex’ is a relative term. These technologies are already in use in a wide range of commercial buildings, from supermarkets and schools to healthcare and heat networks. Training standards are well established and many engineers are fully qualified in the installation and maintenance of natural refrigerant based systems. EU F-gas regulations are steadily tightening restrictions on high-GWP refrigerants, including phase-down quotas and bans on specific HFCs in new equipment. Policy shifts like this accelerate the transition towards low-GWP alternatives, of which natural refrigerants are the most viable, reliable and long-term solution. Our work with propane systems over the past decade and a half proves that, with the right design and execution, these systems can deliver high performing heating solutions for the commercial sector safely and efficiently. The myths persist for now – but in the real world, they’re being discredited, one installation at a time.
