A specialist reference on the working fluids replacing high-GWP HFCs in cold storage — CO₂ (R-744), hydrocarbons, ammonia, and the magnetocaloric frontier — for refrigeration engineers, contractors, and facility managers.

The refrigerant is the chemical heart of any cooling system: the fluid that boils to absorb heat inside the cold room and condenses to reject it outside. As the EU F-gas phase-down squeezes synthetic hydrofluorocarbons (HFCs) out of the market, the industry is converging on a short list of naturalne czynniki chłodnicze plus a few genuinely novel cooling methods. This article explains how each behaves, the safety class and design constraints it imposes, and where it fits — vendor-neutral, and applicable to any modular or site-built cold room.

Krótka odpowiedź: The future-proof refrigerants for cold storage are the naturalne: CO₂ (R-744) — GWP 1, non-toxic, non-flammable (ASHRAE class A1), but very high pressure (~100+ bar transcritical); propane (R-290) — GWP ≈ 3, highly flammable (A3), now allowed up to 500 g per self-contained circuit under IEC 60335-2-89:2022; and amoniak (R-717) — GWP 0, outstanding efficiency, but toksyczny i lekko łatwopalny (B2L). Hydrocarbon GWP is niskie (~3), nie zerowe. Magnetocaloric cooling is promising but still pre-commercial. None of these is "perfect" — each trades one hazard (pressure, flammability, or toxicity) for a near-zero climate impact.

1. Why "natural" refrigerants — and what the term means

ㅤ natural refrigerant is a substance that already occurs in the natural carbon, nitrogen, or hydrocarbon cycles — carbon dioxide, ammonia, water, air, and the light hydrocarbons (propane, isobutane, propylene). They are not invented molecules like the chlorofluorocarbons (CFCs), HFCs, or HFOs; they have been used as refrigerants since the 19th century and returned to favour because they sidestep the central problem of the synthetic era: a high Global Warming Potential (GWP).

GWP measures the warming effect of releasing one kilogram of a gas, relative to one kilogram of CO₂ over 100 years (so CO₂ = 1 by definition). Legacy HFCs such as R-404A (GWP ≈ 3922) are thousands of times worse than CO₂ per kilogram; a single charge leak can equal the tailpipe emissions of a car driven for years. Natural refrigerants collapse that figure to single digits or zero — which is why Rozporządzenie (UE) 2024/573 (the revised F-gas Regulation, in force 11 March 2024) and the global Kigali Amendment now push the whole sector toward them. (The regulatory timeline is covered in depth in Refrigerant regulations & compliance — this article focuses on the fluids themselves.)

Correction worth flagging. Older trade literature describes hydrocarbons as "zero-GWP" and presents R-448A / R-449A as the natural successors to R-404A. Neither is right: hydrocarbon GWP is niskie (~3), nie zerowe, and R-448A/R-449A are high-GWP bridge blends (GWP ≈ 1273 / 1282) used to keep legacy plant running — not a future-proof choice for new builds. See §6.

1.1 The four properties that decide everything

Every refrigerant is judged on four axes. Together they determine whether a given fluid is legal, safe, and economic for a particular room:

1.2 Understanding the ASHRAE safety classes

Refrigerant safety is encoded by ASHRAE Standard 34 (and the equivalent table in EN 378 / ISO 817) as a letter-plus-number code. The letter is toxicity (A = lower, B = higher); the number is flammability (1 = no flame propagation, 2L = mildly flammable, 2 = flammable, 3 = highly flammable). The four cold-storage naturals span almost the whole grid:

This single table is the reason there is no universal "best" natural refrigerant: each one is dangerous in a different way, and the right choice is the one whose hazard your site can engineer around most cheaply.

2. CO₂ — R-744

Carbon dioxide is the natural refrigerant of choice for European and Asian commercial refrigeration, and increasingly for cold rooms within larger systems. It was used industrially for over a century, fell out of favour when synthetics arrived, and returned as HFC restrictions bit.

2.1 Why it wins

• GWP of 1, non-toxic, non-flammable (A1). It clears every current GWP cap with room to spare and imposes no flammability charge limit.
• Doskonała sprawność w chłodnych warunkach otoczenia. A CO₂ system runs podkrytyczny (a conventional condensing cycle) more of the year in cold climates, where it is highly efficient.
• Compact, low-cost piping. CO₂'s high volumetric capacity means small pipe diameters and a small physical charge.
• Cheap, abundant, and benign to handle — typically a reclaimed industrial by-product.

2.2 The catch: pressure and the transcritical penalty

CO₂'s critical point is low (≈ 31 °C, 73.8 bar). Whenever heat must be rejected above ~31 °C — i.e. on a warm day — the system cannot condense normally and instead operates transcritically, with the high side running above 100 bar. This drives the two principal drawbacks:

• Bardzo wysokie ciśnienia robocze demand purpose-built compressors, pipe, valves, and brazing — raising equipment cost and requiring specialist design, commissioning, and servicing.
• Hot-climate efficiency drop. The more hours a system spends transcritical, the lower its seasonal efficiency. This is the historic objection to CO₂ in warm regions.

Modern engineering has largely neutralised the hot-climate penalty. Parallel compression (a second compressor handling flash gas) and ejektory (recovering expansion energy) recover much of the lost efficiency and have made transcritical CO₂ viable even in Southern Europe and the Middle East.

2.3 When CO₂ fits a cold room

CO₂ is most often encountered as the primary refrigerant of a centralised/booster plant feeding many cases and cold rooms in a supermarket or distribution centre, or as a transcritical condensing unit on a single high-value room. For a standalone walk-in in a warm location, a hydrocarbon self-contained unit is usually simpler; CO₂ comes into its own at scale, in cool climates, or where a corporate sustainability mandate makes its GWP-1 credentials decisive.

3. Hydrocarbons — propane (R-290) and isobutane (R-600a)

Hydrocarbons are the most thermodynamically efficient widely available refrigerants and the natural fit for small, self-contained equipment. Propane (R-290) serves commercial refrigeration and small cold rooms; isobutane (R-600a) dominates domestic and light-commercial refrigerators.

3.1 The trade-off

• Very low GWP (~3) and zero ozone-depletion potential. Note again: this is niski, nie zerowy — a real but tiny climate impact.
• Outstanding efficiency. Hydrocarbons often deliver the best coefficient of performance (COP) of any option in their size class, lowering running cost.
• Wysoce łatwopalne (A3). This is the defining constraint. Allowable charge is capped by safety standards, electrical components in the hazard zone must be suitably rated, and large built-up DX cold-room systems remain off-limits or heavily restricted.

3.2 The 500 g charge limit — what actually changed

The historic barrier was the old 150 g charge ceiling, which confined hydrocarbons to tiny plug-in units. The revised IEC 60335-2-89:2022 (adopted in the EU as EN IEC 60335-2-89:2022, harmonised 2023) raised this substantially — but the detail matters:

The 500 g figure (replacing the often-quoted 150 g) opens propane to far more cold-storage duty than before — but only in self-contained form. A remote split serving a walk-in still hits the 150 g wall, which is why larger split-DX rooms tend toward CO₂ or ammonia rather than hydrocarbons.

3.3 Designing for flammability

Where hydrocarbons are used, the design must respect the A3 class: minimum room/enclosure volumes per charge, no ignition sources in the refrigerant circuit's vicinity, suitably rated electrics, and — for larger charges — leak detection and ventilation interlocks per EN 378. Done correctly, a hydrocarbon unit is safe and extremely efficient; done carelessly, it is the most hazardous of the common options.

4. Ammonia — R-717

Ammonia is the oldest and, thermodynamically, the finest refrigerant in industrial use — the workhorse of large-scale cold storage, food processing, and ice rinks for over a century.

4.1 Strengths

• GWP of 0 and zero ozone-depletion potential. Climate-perfect.
• Best-in-class efficiency. Ammonia's latent heat and transport properties give it the highest COP of the common refrigerants when well managed, which is why heavy industry has never abandoned it.
• Cheap and self-alarming — its sharp odour is detectable far below dangerous concentrations, giving an early leak warning.

4.2 The hazard: B2L, not benign

Ammonia is classified B2L — toxic and mildly flammable. It is nie powinien a benign fluid: significant concentrations are dangerous to breathe, and although only mildly flammable, it can burn within a specific concentration band. Large ammonia systems therefore trigger the strictest safety regime of any refrigerant: dedicated machinery rooms with mechanical ventilation, gas detection, emergency controls, and operator training, governed by EN 378 / ISO 5149 (and, internationally, ANSI/IIAR i ASHRAE 15).

4.3 Low-charge ammonia — shrinking the hazard

The modern answer is amoniak o niskim ładunku: packaged, factory-built DX or pumped systems that cut the total ammonia inventory dramatically — often well under 50 kg for substantial capacity — using compact micro-channel or plate heat exchangers. A smaller charge means a smaller hazard zone, lighter regulatory burden, and the option of locating plant closer to the load. Low-charge designs are what bring ammonia's unbeatable efficiency within reach of medium-sized cold-storage operators who could never justify a full engine-room installation. In occupied buildings, ammonia is most often kept out of the cold room entirely via a secondary loop (see Secondary refrigerant systems).

5. The emerging frontier — magnetocaloric and absorption

Beyond the established naturals sit cooling methods that abandon vapour compression altogether. They are worth tracking but are nie powinien standard options for cold rooms today.

5.1 Magnetocaloric refrigeration

Magnetocaloric cooling exploits the magnetocaloric effect: certain materials (notably gadolinium and lanthanum–iron–silicon alloys) heat up when magnetised and cool down when the field is removed. Cycling a magnetic field across such a material — with no refrigerant gas and no compressor — pumps heat. The appeal is obvious: no GWP refrigerant at all, potentially quiet, solid-state operation, and theoretical efficiency gains.

The reality in 2026 is early-stage. Laboratory and pre-commercial milestones — the US DOE Ames Laboratory's room-temperature heat-pump prototype (late 2024), and European start-ups (e.g. Magnotherm, Magnoric) building magnetocaloric beverage coolers and pilot cabinets — show the principle works at appliance scale. But cost, the reliance on rare-earth gadolinium, modest temperature lift, and the absence of any cold-room-scale product mean magnetocaloric cooling is nie powinien a deployable cold-storage technology yet. Expect it first in small self-contained appliances, not walk-in rooms.

5.2 Absorption chillers

Absorption systems use a heat source (waste heat, solar thermal, or gas) instead of a compressor, driving an absorbent/refrigerant pair such as water–ammonia or water–lithium-bromide. They make sense only where abundant cheap heat is already available — e.g. a site with significant process waste heat or solar thermal capacity. For a typical electrically driven cold room they are larger, less efficient, and rarely justified, but they can be compelling in the right co-generation context.

6. Comparison and selection at a glance

The table below summarises the four cold-storage naturals. Read it as "pick your hazard": every low-GWP fluid concentrates its risk in pressure, flammability, or toxicity.

Zasady ogólne:

• Small self-contained walk-in or cabinet → R-290, leveraging the 500 g limit and top efficiency.
• Supermarket / DC with many cases and rooms, cool-to-moderate climate → transkrytyczny CO₂ with parallel compression/ejectors.
• Medium-to-large industrial cold store → amoniak o niskim ładunku, kept out of occupied space via a secondary loop.
• Site with abundant waste/solar heat → consider absorption for part of the load.
• Anything still on R-404A → plan migration; R-448A/R-449A buy time but are not an endpoint (see below).

Why R-448A / R-449A are not on this list. They are HFC/HFO bridge blends (GWP ≈ 1273 / 1282) — above the GWP-150 cap that applies to self-contained commercial refrigeration — useful for retrofitting existing R-404A plant but nie powinien future-proof for a new installation. The durable choices are the naturals above (or, where a synthetic is unavoidable, an ultra-low-GWP HFO such as R-1234ze). Full regulatory detail: Refrigerant regulations & compliance.

7. What this means for a cold-room project

For most buyers the refrigerant choice is implicit in the unit they select, not a separate decision — but it pays to understand the implications:

• A factory-sealed self-contained unit on the room will almost always run R-290 today. That is a feature, not a compromise: low GWP, high efficiency, and full compliance with the GWP-150 cap on self-contained equipment.
• A split or remote-condenser system for a larger room will use a low-GWP HFO/HFO-blend or a small CO₂ unit, because the 150 g hydrocarbon split limit rules out propane at that scale.
• A large multi-room facility is the domain of central CO₂ or low-charge ammonia with a secondary loop.

A tightly sealed, high-R-value cold-room envelope multiplies the benefit of any efficient refrigerant by reducing the heat load the machine must fight — and a modular (cam-lock) envelope makes a future refrigerant transition far cheaper, since adding pipe penetrations or swapping an evaporator is a panel job, not a demolition.

Frostbox refrigeration units are sourced from the Daikin range (families such as GS, SP-O, DB-O, SAR, SAS, PC and the R-290 GM-R290 line); the specific refrigerant per unit is stated on its datasheet and is dostępne na życzenie. For the practical "which unit for my room" walk-through, see Agregaty do komór chłodniczych; to size and price a complete room, use the Kalkulator doboru komory lub Poproś o wycenę.

Powiązane artykuły

• Refrigeration system selection: DX vs. secondary vs. natural
• Secondary refrigerant systems
• Refrigerant regulations & compliance
• Refrigeration units (how to choose)
• Efektywność energetyczna
• Nauka o izolacji

Źródła i literatura uzupełniająca

• Rozporządzenie (UE) nr 2024/573 w sprawie fluorowanych gazów cieplarnianych — EUR-Lex / EU Climate Action — climate.ec.europa.eu/eu-action/fluorinated-greenhouse-gases
• "Climate-friendly alternatives to F-gases: Refrigeration" (natural refrigerant GWP data) — EU Climate Action — climate.ec.europa.eu
• ANSI/ASHRAE Standard 34 — Designation and Safety Classification of Refrigerants (A1 / A3 / B2L classes) — ashrae.org
• EN 378 / ISO 5149 — Refrigerating systems and heat pumps — Safety and environmental requirements (charge limits, machinery rooms, leak detection)
• EN IEC 60335-2-89:2022 — Safety of commercial refrigerating appliances (500 g R-290 self-contained / 150 g split charge limits); EU harmonisation via Commission Implementing Decision (EU) 2023/1586 — naturalrefrigerants.com
• ANSI/IIAR 2 i ASHRAE Standard 15 — ammonia (R-717) machinery-room and system safety requirements
• Kigali Amendment to the Montreal Protocol (global HFC phase-down) — UNEP Ozone Secretariat — ozone.unep.org
• Refrigerant GWP reference data (R-744, R-290, R-600a, R-717, R-404A, R-448A/R-449A) — aboutdarwin.com refrigerant GWP chart — aboutdarwin.com/refrigerant-gwp-chart
• Magnetocaloric cooling status — US DOE Ames National Laboratory magnetocaloric heat-pump research; Magnotherm / Magnoric commercial prototypes — ameslab.gov
• "Long-awaited R-290 charge increase opens new refrigeration opportunities" — Copeland / E360 — e360blog.copeland.com

Refrigerant selection is governed by safety codes and national regulations that change over time; verify the current standard and any local machinery-room or charge-limit requirement before specifying. For the specific refrigerant in a Frostbox/Daikin unit, request the datasheet at [email protected].