Refrigerant Types: R32 vs R410A vs R290 — GWP, Flammability Classes and What Each Means for Installers

Summary

The refrigerant landscape for UK air conditioning engineers has changed significantly and will continue changing through the late 2020s. Understanding the properties, classification, and installation requirements of the main refrigerants in current use is now a core part of the job — not just an academic exercise. Get it wrong and you create safety hazards, fail F-Gas compliance, or leave customers with systems they cannot easily service in five years.

The most important shift currently underway is the transition away from R410A. This refrigerant dominated the residential and light commercial AC market for two decades, but its high GWP of 2088 makes it a target of the UK HFC phase-down. From 2025, new systems using R410A can no longer be placed on the UK market for most air conditioning applications. The replacement in virtually all major manufacturers' split system ranges is R32 — which has a GWP of 675, about one-third that of R410A, but carries a different safety classification (A2L: mildly flammable) requiring adjusted installation practices.

Meanwhile, R290 (propane) is gaining ground in smaller systems — particularly portable and small fixed units — because of its near-zero GWP (3) and excellent thermodynamic properties. However, R290 is classified A3 (highly flammable) and the regulations governing its use in occupied spaces are more stringent than for A2L refrigerants. Engineers who have only ever worked with A1 refrigerants need to understand these differences before taking on R290 work.

A common industry misconception is that A2L refrigerants are hazardous in the same way as A3 refrigerants. This is not correct. A2L refrigerants have a very low burning velocity (≤10 cm/s under ASHRAE 34 criteria) and relatively high minimum ignition energy, meaning they do not ignite easily and propagate flame very slowly when they do. The practical risk from A2L refrigerants in correctly installed and ventilated systems is very low — but the installation standards are specific and must be followed.

Key Facts

• ASHRAE 34 classification — the international standard for refrigerant safety groups, used in BS EN 378 and UK/EU regulations: letters indicate toxicity (A = lower, B = higher), numbers indicate flammability (1 = non-flammable, 2L = mildly flammable, 2 = flammable, 3 = highly flammable)
• R410A GWP — 2088; A1 (non-flammable, lower toxicity); being phased out of new equipment from 2025 in UK
• R32 GWP — 675; A2L (mildly flammable, lower toxicity); dominant refrigerant in new residential and light commercial splits
• R290 (propane) GWP — 3; A3 (highly flammable, lower toxicity); growing use in portable and smaller fixed systems
• R1234yf GWP — 4; A2L (mildly flammable); primarily used in automotive AC but entering some light commercial refrigeration
• R744 (CO₂) GWP — 1; A1 (non-flammable); used in commercial refrigeration cascades, heat pump water heaters; high operating pressures require specialist knowledge
• R134a GWP — 1430; A1 (non-flammable); formerly common in chillers and automotive; being phased out
• A2L burning velocity — ≤10 cm/s (compare: A2 is >10 cm/s; A3 has no upper limit on burning velocity under classification)
• R290 charge limit in occupied spaces — charge per system is limited by BS EN 378-1 based on room volume and occupancy type; typically 150g per occupied space for direct systems [verify current table]
• R32 systems — require ignition-source-free zones around indoor units, A2L-rated components (motors, fans), and adequate ventilation per BS EN 378 and manufacturer specification
• Refrigerant recovery — A2L and A3 refrigerants must be recovered using recovery machines rated and tested for use with flammable refrigerants; using A1-only equipment is unsafe
• Tool requirements for A3 — copper or brass tools preferred; avoid spark-generating tools near open refrigerant circuits; no steel wool, angle grinders, or open-flame soldering near the refrigerant circuit
• Phase-down impact — R410A supply tightening from 2025 onward; engineers should advise customers with R410A systems about long-term servicing cost trajectory and eventual replacement timeline
• R32 and R410A not interchangeable — R32 and R410A use the same pipe sizing in most applications but are not drop-in replacements; recharging an R410A system with R32 is illegal and unsafe

Quick Reference Table

Detailed Guidance

R410A: What You Need to Know for Existing Systems

R410A is a blend of R32 (50%) and R125 (50%) and was the dominant AC refrigerant globally from the mid-1990s until the late 2010s. Its A1 classification made it straightforward to install: no special ventilation, no ignition-source controls, no restrictions on indoor unit location beyond manufacturer clearances.

New equipment using R410A can no longer be placed on the UK market for air conditioning applications from 2025 under the F-Gas phase-down quota restrictions. However, the installed base is enormous — millions of systems across the UK will continue to use R410A for years or decades. Your obligation on these systems is:

• Continue to service and maintain them to the same standard as always
• Be aware that R410A refrigerant prices will rise as bulk supply tightens; factor this into service quotes
• Advise customers with ageing R410A systems (particularly anything over 8–10 years old) that replacement with a lower-GWP alternative is worth planning for, both for environmental reasons and long-term cost certainty
• Never mix R32 into an R410A system (or vice versa) — they are not interchangeable, have different pressures, and mixing them produces a refrigerant of unknown properties

R410A operates at higher pressures than older refrigerants like R22 or R407C — typical high-side pressures of 28–30 bar at normal operating conditions. Recovery equipment, manifold gauges, and hoses must all be rated for these pressures.

R32: The New Standard and What Changes for Installers

R32 is now the refrigerant of choice for virtually all major manufacturers' new residential and light commercial split systems — Daikin, Mitsubishi Electric, Fujitsu, Panasonic, Samsung, and LG have all transitioned their ranges. R32 has a GWP one-third that of R410A and better thermodynamic efficiency, meaning smaller charge weights for the same cooling capacity.

The key change for installers is the A2L flammability classification. The practical implications are:

Indoor unit installation:

• Indoor units must be installed so that any refrigerant leak disperses safely and cannot accumulate near ignition sources
• The manufacturer will specify a minimum room volume for safe installation; if the room is smaller than the minimum, additional ventilation or mechanical extraction may be required
• Do not install indoor units in rooms where there are permanent ignition sources (gas appliances with open flames, certain industrial processes) unless the manufacturer specifically approves it
• A2L-rated motors and fans are required — verify with the manufacturer that the unit supplied meets A2L component requirements (all reputable manufacturers' R32 units should comply, but always check for non-standard or budget equipment)

Recovery and handling:

• Recovery machines must be rated for use with A2L refrigerants; check the machine manufacturer's specification. Using an A1-only machine with R32 is not recommended by equipment manufacturers and may invalidate the machine's warranty or certification
• Avoid sparks and open flames in the vicinity of open refrigerant circuits; this is good practice even with A1 refrigerants but is more critical with A2L
• Store R32 cylinders away from heat sources and ignition points

Leak testing:

• R32 leaks are detectable with standard electronic leak detectors, but the detector must be capable of detecting flammable refrigerants; not all detectors are — check the specification
• Nitrogen pressure testing and bubble testing are unaffected by the flammability classification

In practice, the vast majority of R32 installations in correctly sized rooms with standard ventilation present no meaningful additional risk compared to R410A. The A2L classification is important to understand and respect, but it should not make you apprehensive about R32 work — the manufacturers have designed their systems for safe use with the refrigerant they specify.

R290 (Propane): Installation Rules and Charge Limits

R290 is propane — the same substance used in domestic barbecue cylinders. Its GWP of 3 makes it the most environmentally benign common refrigerant, and its thermodynamic properties are excellent. Its A3 flammability classification (highly flammable) means it requires the most careful handling of any refrigerant in common AC use.

R290 systems currently used in UK air conditioning tend to be smaller — portable air conditioners, small wall-mounted splits with low charges, and some small commercial refrigeration units. Larger multi-split systems using R290 are not yet common in the UK market, though this may change as manufacturers respond to the phase-down.

Charge limits in occupied spaces:

BS EN 378-1 sets maximum refrigerant charge limits for direct systems (where refrigerant flows into the occupied space) based on the refrigerant's Lower Flammability Limit (LFL), room volume, and occupancy category. For R290 in a normal occupied room:

• The practical charge limit for a single circuit in a normally occupied space is in the range of 100–300g depending on room volume and ventilation — significantly lower than typical R32 or R410A charges
• Multi-split systems using R290 must ensure that no single occupied space could accumulate sufficient refrigerant from a full-circuit leak to reach the LFL (equivalent to approximately 8% of the room's air volume containing refrigerant)
• Systems specifically designed for R290 by the manufacturer will have charge sizes calculated to comply with these limits; do not attempt to modify a system to increase its R290 charge

Practical handling rules for R290:

• Use tools and equipment specifically rated for use with flammable refrigerants; avoid anything that can generate sparks in the vicinity of an open refrigerant circuit
• Do not use steel wire brushes, angle grinders, or disc cutters near R290 systems
• Purge pipe runs with nitrogen before and after brazing; do not braze in areas where R290 vapour could accumulate
• Recovery machines must be rated for A3 refrigerants; this is a harder requirement to meet than for A2L — fewer standard recovery machines are rated for A3
• Wear appropriate PPE: safety glasses, and gloves when handling liquid refrigerant (frostbite risk on skin contact)
• Store cylinders upright, away from ignition sources, in well-ventilated areas

Who can work on R290 systems:

Individual F-Gas certification does not cover R290 (propane is not a fluorinated gas). There is currently no mandatory individual certification specifically for R290 work in the UK, but REFCOM's Contractor Competency Scheme (CCS) covers natural refrigerants including R290 at company level. As R290 systems become more common, it is likely that training and competency requirements will be formalised. Engineers taking on R290 work should seek manufacturer training and familiarise themselves with HSE guidance on flammable substances (DSEAR — Dangerous Substances and Explosive Atmospheres Regulations 2002).

R744 (CO₂) and Specialist Refrigerants

R744 (CO₂) has a GWP of 1 — essentially zero climate impact from leaks. It is used in transcritical and subcritical refrigeration systems (supermarket display cases, heat pump water heaters) and increasingly in heat pump systems. Its A1 classification means no flammability concerns, but it operates at very high pressures — typical high-side pressures of 90–120 bar in transcritical operation — which require specialist training, specialist tools, and specialist recovery equipment. Do not work on CO₂ systems without specific manufacturer training.

R1234yf has near-zero GWP (4) and is primarily used in automotive air conditioning. It is beginning to appear in some light commercial refrigeration applications. Its A2L classification means similar precautions to R32 apply.

Telling Customers About R32 and the Phase-Down

Customers with R410A systems will increasingly ask about what happens when their system needs a refrigerant top-up or recharge, and when they should replace their unit. A straightforward answer:

• R410A servicing will remain possible for the foreseeable future — the phase-down affects new supply, but recovered and reclaimed R410A will continue to be available for servicing existing systems. However, prices will rise.
• R32 is safe and widely used — customers should not be alarmed by the A2L classification. Manufacturers have designed their systems to be safe when installed correctly, and millions of R32 systems operate without incident globally.
• System lifespan matters more than refrigerant type — a well-maintained R410A system with five or more years of life left in it does not need replacing for refrigerant reasons alone. A system approaching end of life, or one that has had repeated failures, is worth replacing with a new R32 (or better) unit.
• R290 systems have the best environmental credentials but are currently limited to smaller applications; not a direct replacement for a whole-house multi-split.

Frequently Asked Questions

Can I recharge an R410A system with R32 since they're related?

No. R410A is a 50/50 blend of R32 and R125. R32 alone has different pressure-temperature characteristics, different operating pressures, and different oil compatibility. Charging an R410A system with R32 is illegal (it creates an unregistered refrigerant blend), unsafe, and will likely damage the compressor. Always charge with the refrigerant specified on the equipment label.

Do I need special tools for R32 work?

Your existing manifold gauges and hoses must be rated for the pressures involved (R32 operates at similar pressures to R410A, so R410A-rated equipment is generally suitable). Your recovery machine should ideally be rated for A2L refrigerants — check the manufacturer's specification. Your leak detector should be capable of detecting flammable refrigerants. Beyond that, standard AC tools and techniques apply; no dramatically different tooling is required.

What is the maximum R290 charge I can use in a domestic room?

The exact limit depends on room volume and ventilation, calculated using BS EN 378-1 tables. As a rough rule of thumb, small R290 systems designed for domestic use typically have charges below 300g per circuit. Do not increase the factory charge; the manufacturer has sized it to comply with the relevant standard. If in doubt, ask the manufacturer for their BS EN 378-1 charge limit calculation.

Is R1234yf going to replace R32 in AC systems?

Not in the near term for air conditioning. R1234yf is the dominant refrigerant in automotive AC and is entering some commercial refrigeration applications. In air conditioning, R32 is currently the industry's preferred low-GWP option due to its established supply chain, compatibility with existing system designs, and cost. R1234yf is more expensive to produce. Future generations of AC systems may use different refrigerant blends (some manufacturers are developing GWP-21 and lower blends), but R32 is the realistic standard for new AC installations through at least the end of the decade.

My customer has an R22 system. What should I advise them?

R22 (HCFC) has been illegal to use as a top-up refrigerant in the UK since 1 January 2015. You cannot legally add virgin or reclaimed R22 to any system. If a customer has a working R22 system that has not yet had refrigerant issues, it is operating on its original charge. When it eventually leaks or needs repair involving the refrigerant circuit, the system must be decommissioned and replaced — you cannot legally recharge it. Advise customers with R22 systems to plan for replacement and to consider doing so proactively rather than waiting for a breakdown.

Regulations & Standards

• ASHRAE Standard 34 — Designation and Safety Classification of Refrigerants; the international framework for refrigerant naming and safety classification used in BS EN 378

• BS EN 378 — Refrigerating systems and heat pumps — safety and environmental requirements; Part 1 covers classification and charge limits; Part 2 covers design; Part 3 covers installation siting; Part 4 covers operation, maintenance, repair, and recovery

• UK F-Gas Regulations 2015 (SI 2015/310) — governs HFC refrigerants; does not directly cover R290 or R744 (non-fluorinated)

• DSEAR 2002 — Dangerous Substances and Explosive Atmospheres Regulations; applies to work with A2L and A3 refrigerants in potentially explosive atmospheres

• HSE INDG381 — Working safely with refrigerants; covers flammability and pressure safety for all refrigerant classes

• IEC 60335-2-40 — Safety of household and similar electrical appliances; Part 2-40 covers heat pumps, air conditioners, and dehumidifiers; includes flammable refrigerant requirements (relevant to CE/UKCA marking of equipment using A2L refrigerants)

• Pressure Systems Safety Regulations 2000 (PSSR 2000) — applies to all refrigerant systems; written schemes of examination required for certain system sizes

• ASHRAE Refrigerant Safety Classifications — authoritative source for ASHRAE 34 classification explanations

• HSE: Refrigerant Safety (INDG381) — UK Health and Safety Executive guidance on refrigerant handling

• BS EN 378 — BSI Standards — refrigeration system safety standard covering charge limits and safety requirements

• BESA A2L Refrigerants Guidance — Building Engineering Services Association guidance on A2L installation requirements [verify current publication]

• Environment Agency: F-Gas phase-down — UK HFC quota reduction schedule and refrigerant availability outlook

• f gas regulations guide — F-Gas Regulations: certification, leak check frequencies, and HFC phase-down obligations

• refcom certification — REFCOM company registration including the Contractor Competency Scheme for natural refrigerants

• split system installation — practical split system installation guide covering R32-specific ventilation and component requirements

• multi split system design — refrigerant charge calculations and pipe sizing for multi-split systems

• ac maintenance annual service — annual service requirements including refrigerant checks and leak detection