Every refrigerant carries an R-number under ASHRAE Standard 34. It is not a product-approval code, it is a chemistry/designation cue. Once you can read it, an unfamiliar number gives useful context, but the exact safety class, GWP basis, blend composition, application status, charge limits, and compatibility still need current ASHRAE, EPA, SDS, manufacturer, code, AHJ, and qualified review.
Single Compounds: Counting Atoms
For a single-compound refrigerant the digits count atoms in the molecule:
- The ones digit is the number of fluorine atoms.
- The tens digit is the number of hydrogen atoms plus one.
- The hundreds digit is the number of carbon atoms minus one (left off when it is zero, which is the single-carbon methane series).
Chlorine fills whatever bonds are left over. Run R-22 through it: ones digit 2 (two fluorines), tens digit 2 (one hydrogen), no hundreds digit (one carbon). A single carbon has four bonds, minus one hydrogen and two fluorines leaves one chlorine. That is CHClF2, a hydrochlorofluorocarbon (HCFC). R-32 works out to one carbon, two hydrogens, two fluorines, no chlorine: a clean HFC.
Refrigerant Designation Decoder
Decode any refrigerant R-number (R-410A, R-32, R-1234yf, R-22, R-744). Explains the ASHRAE 34 numbering rules digit by digit, then gives the chemical family, blend composition, safety class, ODP, GWP, temperature glide, and what the refrigerant replaces or is replaced by. Reuses ToolGrit's shared refrigerant dataset so the numbers match the P-T chart and charge tools.
What the Family Tells You
The atoms determine the family, and the family tells you the environmental story:
- CFC (chlorine, no hydrogen) and HCFC (chlorine and hydrogen) contain chlorine, which depletes ozone. These are the phased-out legacy refrigerants like R-12 and R-22.
- HFC (hydrogen and fluorine, no chlorine) has zero ozone depletion but often a high global warming potential. R-134a and R-410A are HFCs.
- HFO (an unsaturated HFC, with a carbon-carbon double bond) breaks down quickly in the atmosphere and has a very low GWP. R-1234yf is an HFO.
- Hydrocarbons (R-290 propane) and inorganics (R-744 CO2) are natural refrigerants with very low GWP.
Blends: the 400 and 500 Series
When a refrigerant is a mixture, it gets a 400 or 500 series number instead of an atom-count number.
- 400 series blends are zeotropic: the components boil at different temperatures, so the blend has temperature glide.
- 500 series blends are azeotropic: they behave like a single compound, with negligible glide.
The numbers are assigned in order, so they do not encode the composition directly. The trailing capital letter (A, B, C) distinguishes blends made of the same components in different ratios. R-407C and R-407A are the same three components in different proportions.
The Safety Class
The safety class is two parts. The letter is toxicity: A is lower toxicity, B is higher. The number is flammability: 1 is no flame propagation (non-flammable), 2L is mildly flammable with a low burning velocity, 2 is flammable, and 3 is highly flammable. So R-410A is A1 (non-flammable), R-32 and R-454B are A2L (mildly flammable), and propane R-290 is A3 (highly flammable).
ODP, GWP, and Glide
ODP (ozone depletion potential) is referenced to CFC-11 at 1.0, while HFCs have zero ODP because they do not contain chlorine. GWP (global warming potential) compares a gas to CO2 over a selected time horizon, but AR4, AR5, AR6, product-data, EPA program, and reporting-year bases can differ. Glide is the temperature spread of a zeotropic blend as it changes phase; fractionation and leak response must be handled through the SDS, product data, manufacturer procedure, EPA rules, and qualified HVAC review, not this guide.