1 Refrigerant Types and Classification
Learn how refrigerant families, R-numbers, blend designations, and ASHRAE safety classes describe refrigerants, and how to verify labels and system compatibility before use.
How refrigerants are identified
Refrigerants are identified by their chemical family, , and . These labels help technicians determine what a refrigerant is and what hazards and equipment requirements may apply. A refrigerant’s identity alone does not establish that it is suitable for a particular system; follow the , manufacturer instructions, and applicable safety requirements.
Refrigerant families and their patterns
Families indicate broad chemical and environmental patterns, but they do not provide a complete application list or a full assessment of a refrigerant’s safety. A refrigerant can have more than one environmental or safety consideration: low does not rule out flammability, toxicity, or high operating pressure.
CFCs (chlorofluorocarbons) contain chlorine, fluorine, and carbon. Many older refrigerants are CFCs; they can deplete stratospheric ozone, and many also have high . R-12 was used in older vehicle air conditioners and refrigeration equipment and is mainly encountered in legacy systems.
HCFCs (hydrochlorofluorocarbons) contain hydrogen, chlorine, fluorine, and carbon. They deplete ozone, generally less than CFCs, and many also have significant . R-22 was widely used in older air-conditioning and refrigeration systems.
HFCs (hydrofluorocarbons) contain hydrogen, fluorine, and carbon, but no chlorine. They do not significantly deplete the ozone layer, although many have high . R-134a has been used in vehicle air conditioning and chillers; R-404A in commercial refrigeration; and R-410A in many air-conditioning systems.
HFOs (hydrofluoroolefins) are unsaturated fluorinated refrigerants often discussed separately from conventional HFCs. Many have lower than older options, and some are mildly flammable and classified A2L. R-1234yf is used in many newer vehicle air-conditioning systems; R-1234ze is used in selected refrigeration and cooling applications.
include propane and isobutane. They generally have very low and no ozone-depletion potential, but are often highly flammable. R-600a (isobutane) is common in domestic refrigerators; R-290 (propane) is used in certain purpose-designed refrigeration and air-conditioning equipment.
Inorganic refrigerants include simple compounds such as carbon dioxide and ammonia. They often have low or negligible direct climate impact compared with high- fluorinated gases, but system and safety tradeoffs matter. R-744 (CO₂) is used in commercial refrigeration and heat-pump systems. R-717 (ammonia) is used in industrial refrigeration and has significant toxicity hazards.
R-numbers and blend designations
An is a standardized refrigerant identifier, not a complete description of hazards or suitability. A trailing lowercase letter can distinguish isomers, as in R-134a. A trailing uppercase letter can distinguish blends with different component proportions, as in R-407C.
The 400 series generally identifies zeotropic blends, whose liquid and vapor compositions differ. During boiling or condensation at constant pressure, their temperature can change; this change is called temperature glide. The 500 series identifies azeotropic blends, which behave as constant-composition mixtures at a specified pressure. Check a blend’s technical data to confirm its behavior.
For a , technicians commonly charge from the cylinder’s liquid phase, following the equipment and refrigerant manufacturer’s instructions, to reduce the risk of changing the blend composition. Some inorganic refrigerants use familiar three-digit numbers: R-717 is ammonia, and R-744 is carbon dioxide.
Toxicity and flammability classes
ASHRAE Standard 34 assigns a two-character safety group based on toxicity and flammability. Read both characters together:
A means lower toxicity under the standard’s classification criteria; B means higher toxicity.
1 means no flame propagation under the specified test; 2 means lower flammability; 2L is a lower-flammability subclass with low burning velocity; 3 means higher flammability.
Examples of the classes include:
A1: lower toxicity and no flame propagation. Examples are R-134a, R-410A, and R-744.
A2L: lower toxicity and mild flammability, with low burning velocity. Examples are R-32 and R-1234yf.
A3: lower toxicity and higher flammability. Examples are R-290 and R-600a.
B2L: higher toxicity and lower flammability with low burning velocity. Ammonia, R-717, is classified B2L; consult current ASHRAE classification tables for specific refrigerants.
A safety class describes standardized hazard categories; it does not mean a refrigerant is harmless. A1 refrigerants can still displace oxygen, cause cold burns, or create dangerous pressures. A2L and A3 refrigerants require equipment and work practices appropriate to their flammability. Check current ASHRAE tables and the refrigerant’s safety data sheet rather than guessing its class from its family.
Labels and system compatibility
Identify a refrigerant by checking both the and the cylinder label; do not identify it by cylinder color alone. Color requirements have applied to some specific motor-vehicle refrigerants, but color is not a universal identification system. Read the printed refrigerant designation and consult the for hazards, handling, and emergency information. Equipment labels may also state the required refrigerant and factory charge.
Before using or considering a substitute, verify each of the following:
System approval and design: The compressor, coils, pressure controls, heat exchangers, and other components must be designed or approved for that refrigerant. Similar-looking systems are not necessarily compatible.
Operating pressure and performance: Compare the refrigerant’s pressure–temperature behavior and capacity with the system’s design limits. The pressure difference between R-410A and R-22 is one reason an R-22 indoor coil is not compatible with R-410A.
Lubricant and materials: Check lubricant type and compatibility with seals, hoses, and other materials. Retrofit requirements vary by refrigerant and equipment; do not assume existing oil or components will work.
Safety class and charge limits: Flammability or toxicity may require different equipment, ventilation, leak mitigation, or other safeguards. Follow applicable codes, standards, and manufacturer procedures.
Correct identity and service information: Never mix refrigerants or charge by pressure alone. Use the refrigerant specified for the equipment, suitable instruments, and the manufacturer’s charging procedure.
R-410A and R-22 are both used in air-conditioning contexts, but they are not interchangeable on that basis. An R-22 indoor coil is not compatible with R-410A because of pressure differences. A conversion requires a verified, approved retrofit path, not simply replacing the refrigerant.