ASHRAE and the United Nations Environment Programme have
released an April 2026 fact sheet updating refrigerant designations and safety classifications under ASHRAE standards. The document introduces refrigerants that have received “R” numbers in recent years and entered the international market.
ASHRAE Standard 34, Designation and Safety Classification of Refrigerants, provides a system for referring to refrigerants by assigned numbers rather than chemical names, formulas or trade names. ASHRAE assigns refrigerant numbers and safety classifications based on toxicity and flammability data submitted by producers.
The fact sheet explains that refrigerants are identified with an R- followed by an ASHRAE-assigned number. Isomers use a lower-case letter after the number, while blends with the same pure components but different compositions use an upper-case letter. Refrigerants in the R-4xxx or R-4xxxx series are zeotropic blends, while R-5xxx refrigerants are azeotropes.
Standard 34 classifies refrigerants by toxicity and flammability. Class A denotes lower toxicity, while class B denotes higher toxicity. Flammability classes include class 1 for refrigerants that do not propagate a flame, class 2 for lower flammability and class 3 for highly flammable refrigerants. Subclass 2L identifies class 2 refrigerants that burn very slowly.
The publication also references ASHRAE Standard 15, Safety Standard for Refrigeration Systems, which sets requirements intended to help protect people and property where refrigeration facilities are located. It notes possible risks including rupture, refrigerant release, fire, deflagration, inadequate ventilation, toxic effects, corrosive attack and tissue freezing from contact with liquid.
The tables list approved refrigerant numbers from the latest edition of Standard 34 and addenda assigned from 2010 onward. The list includes safety groups, GWP100 values where available, and boiling, bubble and dew point data. The fact sheet states that the list is not intended to be complete or definitive and refers users to the latest ASHRAE Standard 34 and published addenda for complete information.
