By Yevhen Kovalchuk · Updated August 7, 2026 · 7 min read
Short answer
Ammonia (R-717) is the standard refrigerant for large industrial plants because it is efficient, inexpensive and has no ozone or direct global warming impact, but it is toxic and brings process safety obligations. Freon-type HFC and HFO systems are common in small and mid-size commercial refrigeration because they are non-toxic at normal levels and use standard components, but they face a refrigerant phasedown. The right choice depends mainly on system size, location and the people who will operate it.
Ammonia (R-717) is generally the better fit for large industrial refrigeration plants, while HFC and HFO “Freon-type” refrigerants dominate small and mid-size commercial systems. Ammonia is more efficient and has no ozone depletion or direct global warming potential, but it is toxic and flammable at high concentrations, so it requires careful design and trained operators. Synthetic refrigerants are safer to be around, easier to service with common parts, but they face regulatory phasedowns and typically cost more to buy and replace.
“Freon” is a brand name that people often use for any fluorinated refrigerant. This article uses “HFC and HFO” for the modern synthetic refrigerants and covers how they compare with ammonia.
How do ammonia and HFC or HFO refrigerants compare?
| Factor | Ammonia (R-717) | HFC / HFO refrigerants |
|---|---|---|
| Typical size | Large: cold storage, food processing, ice rinks | Small to mid-size: grocery, walk-ins, rooftop and split systems |
| Energy efficiency | Excellent thermodynamic properties | Good, varies by refrigerant and design |
| Toxicity | Toxic, strong odor gives early warning | Low toxicity at normal levels, asphyxiant in large leaks |
| Flammability | Low, but flammable in narrow conditions | Ranges from non-flammable to mildly flammable (A2L) |
| Environmental impact | Zero ozone depletion, no direct global warming potential | Zero ozone depletion, but HFCs have significant global warming potential |
| Refrigerant cost | Low | Moderate to high, and rising for HFCs under the phasedown |
| Materials | Steel; no copper or brass in contact | Copper, brass, aluminum common |
| Regulation | OSHA PSM and EPA RMP above thresholds | EPA Section 608 and the AIM Act phasedown |
Why is ammonia so efficient?
Ammonia has a high latent heat of vaporization, so each pound of refrigerant moves a lot of heat. That means smaller pipes and lower mass flow for large capacities. Combined with good heat transfer properties and low cost per pound, it helps explain why most large cold storage facilities worldwide are built around it. Actual system efficiency still depends on design: condensing pressure control, evaporator selection, defrost method and compressor type matter as much as the refrigerant. For a plain-language introduction, see ammonia refrigeration system basics.
What are the safety trade-offs?
Ammonia is toxic and irritating at low concentrations. The same strong odor that makes small leaks easy to notice also makes a large release serious. Systems rely on:
- Leak detection and ventilation, with alarms at defined concentration levels
- Emergency shutdown and pressure relief designed to recognized standards
- Trained operators and written emergency procedures
- Limiting the quantity of ammonia in occupied areas, for example with low-charge or packaged designs
HFC and HFO refrigerants have lower direct toxicity, but they are not harmless: they can displace oxygen in enclosed spaces, and some newer options are mildly flammable. See A2L refrigerants explained.
How are the two regulated?
Large ammonia systems may be subject to OSHA Process Safety Management and the EPA Risk Management Program when the charge exceeds a threshold. We summarize those programs in OSHA PSM and EPA RMP for ammonia facilities.
Synthetic refrigerants fall under EPA’s Section 608 rules for handling, leak repair and recordkeeping, plus the American Innovation and Manufacturing (AIM) Act, which phases down HFC production and consumption. Thresholds and schedules change, so confirm them in current rule text. Related reading: what is the AIM Act HFC phasedown and EPA 608 leak repair rules.
What drives the cost of each option?
- Installed cost. Ammonia plants usually have higher engineering, piping, safety system and permitting costs, which pay off at larger sizes. Small systems rarely justify them.
- Refrigerant cost. Ammonia is cheap per pound. HFC prices rose as the phasedown tightened supply.
- Operating cost. Energy is usually the largest lifetime expense. Ammonia’s efficiency can lower it in large, long-running plants.
- Compliance cost. Process safety documentation, audits and training for ammonia; leak detection, repair and recordkeeping for HFCs.
- Labor. Ammonia work requires specialized knowledge, and qualified people are in short supply in many regions.
Where does each one fit best?
- Large cold storage and food processing. Ammonia, often with a liquid overfeed or pumped system.
- Mid-size facilities. Either, or an ammonia/CO2 cascade that limits the ammonia charge. See CO2 transcritical refrigeration.
- Grocery stores and small commercial refrigeration. HFC or HFO systems, or CO2.
- Walk-in coolers and freezers. Packaged synthetic-refrigerant condensing units. See walk-in freezer vs walk-in cooler.
- Comfort cooling and chillers. Mostly synthetic refrigerants, with propane in some small chillers.
Frequently asked questions
Is ammonia more dangerous than Freon?
They carry different risks. Ammonia is acutely toxic in a large release, but its odor warns people at low levels. Synthetic refrigerants are less toxic but can still cause asphyxiation in confined spaces, and some are flammable. Safety comes from design to recognized standards, maintenance and trained operators, not from the refrigerant alone.
Can you convert an ammonia system to HFC, or the reverse?
Technically it can be done, but it is a major redesign, not a swap. Materials, pressures, compressors, oil and safety systems all differ. Most owners compare conversion against a new design before deciding.
Why do some plants use ammonia with CO2?
In a cascade, ammonia works on the high-temperature side in a small, contained area, and CO2 carries the cold to the freezers or coolers. The design limits how much ammonia sits near occupied spaces while keeping ammonia’s efficiency.
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