The "gas" in an air conditioner is its refrigerant, the fluid that carries heat out of the room. In the UK, almost every new split system now uses R32. Older systems mostly run on R410A or R407C, and some very old ones still hold R22, which has been banned for servicing since 2015. Larger systems may use R454B, R134a or natural refrigerants such as propane and CO2.
Which gas a system uses decides what it costs to service, which rules apply to it and how long it makes sense to keep it. Here is each one, with its climate impact as GOV.UK lists it and where it stands in Great Britain as of November 2026.
Air conditioning refrigerants at a glance
| Refrigerant | Type | GWP | Safety class | Status in Great Britain |
|---|---|---|---|---|
| R32 | HFC | 675 | A2L (lower flammability) | The standard in new split air conditioners |
| R410A | HFC blend (HFC-32 and HFC-125) | 2,088 | A1 (non-flammable) | Banned in new single splits under 3 kg since 2025. Still serviced, still used in larger systems |
| R407C | HFC blend | 1,774 | A1 | Banned in new single splits under 3 kg since 2025. Still serviced |
| R22 | HCFC, ozone-depleting | Regulated as an ozone-depleting substance | A1 | Cannot be used for servicing since 1 January 2015 |
| R454B | HFO/HFC blend | 466 | A2L | Used in some larger air conditioning and heat pump systems |
| R134a | HFC | 1,430 | A1 | Common in chillers and older equipment. Subject to the HFC phase-down |
| R290 (propane) | Hydrocarbon, not an F gas | Very low | A3 (higher flammability) | Monobloc heat pumps and some small sealed units |
| R744 (CO2) | Natural refrigerant | 1 | A1 | Mainly commercial refrigeration and some heat pumps |
GWP figures for the HFCs are from the GOV.UK F gas list. R454B's figure is the manufacturer's, Chemours, and CO2 is the reference gas with a GWP of 1 by definition.
What GWP and the safety classes mean
Global warming potential compares the warming effect of a kilogram of gas with a kilogram of CO2 over a hundred years. R410A at 2,088 means a kilogram leaked has the effect of just over two tonnes of CO2. It is also how the F gas rules work out leak check duties: multiply the charge in kilograms by the GWP, and any system at 5 tonnes of CO2 equivalent or more needs regular checks and records.
The safety class has two parts. The letter is toxicity, and A means lower toxicity. The number is flammability: 1 means no flame propagation, 2L lower flammability, and 3 higher flammability. Chemours describes A2L refrigerants as having "mild flammability, low toxicity". That is why R32 and R454B systems need installers trained in the current safety standards, and why propane is limited to smaller, sealed charges.
The refrigerants in more detail
R32
R32 has replaced R410A in almost every new single split sold in Great Britain. Its GWP of 675 is about a third of R410A's, it works at similar pressures, and it is a single gas rather than a blend, which makes it simpler to handle. Our guide to R32 refrigerant covers what it means for owners and installers.
R410A
R410A was the standard for the best part of two decades. Since 1 January 2025, single split systems holding less than 3 kg cannot be placed on the GB market if they use a gas with a GWP of 750 or more, which rules it out in that equipment. Existing systems can still be serviced with it, and larger systems such as multi-splits and VRF can still be supplied with it. Its supply tightens again on 1 January 2027, when the HFC quota falls from 31% to 24% of the baseline. Our R410A phase-out guide has the full detail.
R407C and R22
R22 is a hydrochlorofluorocarbon that damages the ozone layer, and it is regulated separately from F gases. Under the retained ozone-depleting substances regulation, reclaimed and recycled HCFCs could only be used to service existing equipment until 31 December 2014. Since 1 January 2015, an R22 system cannot legally be refilled, so any fault on the refrigerant side usually ends its life.
R407C was the standard R22 replacement of its day and many systems were converted to it. It is an HFC with a GWP of 1,774, still legal to service, but caught by the same 2025 single split ban as R410A. If you have either, our guide to whether to repair or replace R22 and R407C systems will help you decide.
R454B
R454B is a blend of an HFO and an HFC that Chemours sells as Opteon XL41, with a GWP of 466, which it describes as a 78% reduction on R410A. It is an A2L refrigerant, used in some larger systems designed around it.
Propane, CO2 and the natural refrigerants
Propane (R290) and CO2 (R744) are not F gases, so they sit outside the HFC quota entirely. Propane is efficient but highly flammable, which limits charge sizes and keeps it to monobloc heat pumps and small sealed equipment. CO2 runs at very high pressures and is mainly used in commercial refrigeration and some heat pumps. Our guide to natural refrigerants explains where each one fits.
How to find out which gas your system uses
Look at the rating plate on the outdoor unit. It states the refrigerant, usually as R32, R410A, R407C or R22 (sometimes HCFC-22), and the factory charge in kilograms. Your service records and F gas register should show the same, along with any gas added since installation.
If the plate says R22, the system cannot be regassed. If it says R410A or R407C, it can be serviced, but plan its replacement before a major leak forces the decision.
"Freon" and other names you will see
Freon is a trade name, and in the UK people often use it to mean any air conditioning gas, especially R22. American articles also call R410A "Puron". Neither name tells you which refrigerant a particular system actually uses, so go by the R number on the rating plate.
Topping up the gas
A system that needs gas has a leak. Refrigerant does not get used up. Under the F gas regulation, a leak must be repaired "without undue delay", and the gases can only be sold to and bought by certified businesses, so a top-up is a job for an F gas certified engineer who should find and fix the leak first. Regular air conditioning maintenance catches small leaks before they become a full recharge.
Questions people ask about air conditioning gas
What gas is used in air conditioning in the UK?
New split air conditioners almost all use R32. Many systems installed in the 2000s and 2010s use R410A, some older ones R407C, and some very old systems still hold R22. Larger systems may use R454B or R134a, and some heat pumps use propane or CO2.
Is R22 banned in the UK?
R22 cannot be used to service air conditioning in the UK. Reclaimed and recycled R22 could only be used for servicing until 31 December 2014, so since 1 January 2015 an R22 system cannot legally be refilled. You can keep running one until it develops a refrigerant fault.
What is the difference between R32 and R410A?
R32 is a single HFC with a GWP of 675 and an A2L lower flammability classification. R410A is a blend of R32 and R125 with a GWP of 2,088 and is non-flammable. R32 is now standard in new splits, while R410A is banned in new single splits under 3 kg but can still be serviced.
Is R32 flammable?
Mildly. R32 is classed A2L, meaning lower toxicity and lower flammability. It is now the standard gas in new split systems, and installers need to follow the current safety standards for charge sizes, ventilation and handling.
Can I top up my air conditioning gas myself?
No. The F gas regulation only allows these refrigerants to be sold to and bought by certified businesses, and work on the refrigerant circuit needs F gas qualifications. A system that needs gas has a leak, which has to be found and repaired.
Can I put a different refrigerant in my air conditioner?
Not simply. Each refrigerant needs equipment designed and rated for it, and a system cannot be switched from R410A to R32 by changing the gas. Some older R22 systems were converted to replacement blends years ago, but for most systems today the realistic answer is to keep servicing the existing gas until replacement.
Planning a system around the right gas
If you are replacing an older R22, R407C or R410A system, the refrigerant for the new one is usually decided for you, but it is worth checking which gas and charge each quote includes. If you would like a straight answer on an existing system or a replacement, you can ask us for a quote and we will put the refrigerant and charge in writing.
Last updated: 4 November 2026
Written by
Ali Elm
Ali is the Head of Operations at Be Cool Refrigeration with over a decade of hands-on experience in HVAC and commercial refrigeration. He oversees every installation, repair, and maintenance project, making sure the work meets the highest standards. Ali holds full F-Gas certification and has worked across residential, commercial, and industrial refrigeration systems throughout London and the South East. When he is not on site, he writes these guides to help business owners and homeowners understand their cooling systems better.