Ammonia (NH3) is the most energy-efficient and lowest-operating-cost refrigerant and dominates large industrial cold storage, but it is toxic and requires formal process-safety management over threshold quantities. HFC "Freon" blends are simple and cheap to install for small and medium facilities, but they carry high global-warming potential and are being phased down under the AIM Act. CO2 (R-744) is a low-GWP natural refrigerant gaining share, usually in cascade or transcritical systems, at higher capital cost. Facility size, temperature, sustainability goals, and regulatory exposure drive the choice.
The refrigerant and refrigeration architecture you choose shape a cold storage facility's energy cost, capital cost, safety program, and regulatory exposure for decades. This guide compares the three dominant options — ammonia, HFC "Freon," and CO2 — and explains which fits which facility.
Ammonia (NH3 / R-717)
Ammonia is the workhorse of large industrial cold storage. It is the most thermodynamically efficient common refrigerant, has zero ozone-depletion and zero global-warming potential, and costs little per pound. The tradeoff is safety: ammonia is toxic and mildly flammable, so above threshold quantities (commonly 10,000 pounds) facilities fall under OSHA Process Safety Management (PSM) and EPA Risk Management Program (RMP) rules, requiring formal safety systems and trained operators. For large warehouses and processing plants, ammonia's efficiency usually justifies that overhead.
HFC "Freon" (R-404A, R-448A and similar)
HFC blends — what most people mean by "Freon" — are simple, familiar, and inexpensive to install, with no PSM burden at typical charges. That makes them common for small and medium facilities. Their weakness is environmental: many HFCs have very high global-warming potential (R-404A is roughly 3,900 times that of CO2), and the AIM Act is phasing down HFC production through 2036, with EPA rules restricting high-GWP HFCs in new equipment. That is steadily raising refrigerant cost and pushing new builds toward lower-GWP options.
CO2 (R-744)
CO2 is a natural refrigerant with negligible global-warming potential (a GWP of 1), no toxicity concern at normal use, and strong cold-temperature performance. It runs at high pressure and is used in cascade systems (often paired with ammonia) or transcritical systems. Capital cost and the need for specialized service are higher, but CO2 is gaining share as a future-proof, low-GWP choice, especially where sustainability goals or the HFC phasedown make it attractive.
Refrigerants at a glance
| Factor | Ammonia (NH3) | HFC "Freon" | CO2 (R-744) |
|---|---|---|---|
| Global-warming potential | 0 | High (e.g. R-404A about 3,900) | 1 |
| Energy efficiency | Highest at scale | Moderate | High at low temperatures |
| Capital cost | Higher for small; efficient at scale | Lowest | Higher |
| Safety / regulatory | Toxic; PSM/RMP over threshold | Simple; HFC phasedown | High pressure; specialized service |
| Best fit | Large industrial cold storage | Small to medium facilities | Sustainability-driven new builds |
Which is right for your facility?
- Large industrial warehouses and processing. Ammonia's efficiency typically wins, and the PSM program is manageable at that scale.
- Small to medium facilities. HFC systems are simple and cheap today, but weigh the phasedown's long-term cost; a low-GWP system may be the better lifecycle choice.
- Sustainability or future-proofing priorities. CO2 (often in an ammonia/CO2 cascade) avoids HFC phasedown risk and meets low-GWP goals.
- Operator capability. Ammonia and CO2 need trained operators and specialized service; that should factor into the decision.
Regulatory direction
The clear trend is away from high-GWP HFCs. The AIM Act's phasedown and EPA technology-transition rules are restricting high-GWP refrigerants in new equipment, which is steadily moving new cold storage toward natural refrigerants — ammonia at scale and CO2 for lower-charge or sustainability-driven systems. Designing around a low-GWP path protects a facility from rising HFC costs and future restrictions.
Frequently asked questions
Why is ammonia used in cold storage?
Ammonia is the most energy-efficient common refrigerant, costs little per pound, and has zero global-warming potential. For large industrial cold storage, those operating-cost advantages outweigh the safety-management overhead it requires.
Is Freon being banned?
High-GWP HFCs are being phased down, not instantly banned. The AIM Act is reducing HFC production through 2036, and EPA rules restrict high-GWP HFCs in new equipment, which is raising their cost and pushing new builds toward lower-GWP refrigerants.
What is Process Safety Management (PSM)?
PSM is an OSHA program for facilities with hazardous chemicals above threshold quantities — commonly 10,000 pounds of ammonia. It requires formal procedures, mechanical-integrity programs, operator training, and documentation to manage the risk.
Is CO2 refrigeration good for cold storage?
Yes, increasingly. CO2 is a low-GWP natural refrigerant with strong low-temperature performance, used in cascade or transcritical systems. It costs more to install and service but avoids HFC phasedown risk, making it attractive for new and sustainability-focused facilities.
Which refrigerant is most efficient?
Ammonia is generally the most energy-efficient for industrial cold storage. CO2 performs very well at low temperatures and in cascade systems, while HFCs are typically less efficient than ammonia at scale.
Plan your refrigeration system
Refrigerant choice is a long-term decision that affects energy cost, safety programs, and regulatory exposure — and it should be made alongside facility size and temperature, not after. To scope the right system for your facility, contact our team or email contact@uscoldstoragebuilders.com. You can also explore cold storage construction, frozen storage construction, our guide on refrigerated vs. frozen storage, and how long it takes to build a cold storage facility, where refrigeration lead time drives the schedule.