1 Refrigerant Types and Properties
Learn how refrigerant families differ in applications, environmental effects, operating conditions, safety classifications, equipment compatibility, and handling requirements.
How refrigerants work
A absorbs heat as it evaporates and releases heat as it condenses. It must also suit the system's operating temperatures, pressures, materials, lubricant, and safety requirements. No is ideal for every application.
families and their uses
Ozone-depleting legacy families
are generally stable and nonflammable, but released deplete stratospheric ozone and can persist as greenhouse gases. They have been phased out of new production in many uses, and equipment containing them is legacy equipment. R-12 was used in older refrigerators and vehicle air conditioners; R-11 was used in older chillers.
also deplete ozone, though generally less than . R-22 is found in older residential and commercial air conditioners and heat pumps. Equipment using it remains in service, but R-22 is a legacy option rather than a choice for most new systems.
Families with zero ozone-depletion potential
have zero ozone-depletion potential, but many have high GWP. R-410A has been used in many older-generation residential and light-commercial air conditioners and heat pumps; R-134a in vehicle air conditioning and some chillers; and R-404A in commercial refrigeration. Some HFC blends, such as R-410A, are nonflammable and classified A1.
and HFC/HFO blends typically have much lower GWP than older and zero ozone-depletion potential. R-1234yf is widely used in newer vehicle air conditioning, while R-32 and R-454B are used in newer air-conditioning and heat-pump equipment designed for them. Other blends are used in selected refrigeration and chiller applications.
Hydrocarbon and inorganic refrigerants
Hydrocarbons such as R-600a (isobutane) and R-290 (propane) have very low GWP and zero ozone-depletion potential. They are used in household refrigerators and selected self-contained refrigeration or room-air-conditioning equipment, respectively. They are highly flammable (A3), so their use is limited to appropriately designed equipment and applicable charge and safety requirements.
Inorganic or “natural” refrigerants include R-744 (carbon dioxide) and R-717 (ammonia). Carbon dioxide is used in commercial and industrial refrigeration, including transcritical systems; it has a GWP of 1 but operates at very high pressures in many systems. Ammonia is used in industrial refrigeration and has excellent heat-transfer properties and no ozone-depletion potential, but is toxic at hazardous concentrations and classified B2L. Each requires systems designed for its specific hazards and operating conditions.
GWP values do not by themselves establish suitability or total impact. impact also depends on energy efficiency, leaks, and recovery or disposal. GWP values may vary by assessment method.
Understanding safety classifications
combine a letter for toxicity classification and a number for flammability. A denotes the lower-toxicity class, while B denotes the higher-toxicity class. Class 1 refrigerants do not propagate a flame under the standard test; Class 2 refrigerants have lower flammability; and Class 3 refrigerants have higher flammability. The designation 2L identifies a lower-flammability with low burning velocity.
The combined designations describe both classifications: A1 means lower toxicity and no flame propagation in the test; A2L means lower toxicity and mild flammability; A3 means lower toxicity and high flammability; and B2L means higher toxicity and mild flammability.
A classification does not mean a is harmless. Leaks can displace oxygen, liquid can cause cold burns, and exposure to flames or hot surfaces can produce hazardous decomposition products.
Pressure and equipment compatibility
Pressure is a property at a specified temperature and condition, not a single fixed value for an entire family. Use the equipment nameplate, manufacturer’s service data, and the correct . Do not infer safe operating pressure or substitute a based only on its family name.
R-744 systems illustrate why the system design matters: they may operate at much higher pressures than conventional comfort-cooling systems. Refrigerants also differ in lubricant compatibility, capacity, and blend behavior, so use only the specified for the equipment.
Safe service and handling
Identify the from the equipment label before connecting gauges or recovery equipment. Follow the manufacturer’s service instructions and the safety data sheet. Use equipment rated for the and its pressures, ventilate the work area, and control ignition sources when working with flammable refrigerants.
In the United States, generally applies to technicians whose work can release from stationary air-conditioning or refrigeration equipment. Intentional venting of ozone-depleting refrigerants and most substitutes during service, repair, or disposal is prohibited.
Recover into an appropriate cylinder rather than releasing it. Do not mix refrigerants; use the applicable recovery, recycling, or reclamation process.