The ASHRAE 34 and ISO 817 standards give every refrigerant a two-character class. The letter indicates toxicity: A, no toxic effect observed below 400 ppm; B, toxic. The number indicates flammability: 1 non-flammable, 2L mildly flammable (flame spreads slowly), 2 flammable, 3 highly flammable. The class determines where the system may be installed, the permitted charge and the safety measures required.
Common refrigerants: A1 — R404A, R449A, R448A, R134a, R410A, R744 (CO₂; non-flammable but asphyxiating at high concentrations). A2L — R32, R1234yf, R454C, R455A (new-generation low-GWP blends). A3 — R290 (propane), R600a (isobutane). B2L — R717 (ammonia).
A1 refrigerants can be installed anywhere with the fewest restrictions. For A2L systems EN 378 requires certain room volume and charge limits and in some cases gas detection; technician training is needed. With A3 the charge is usually limited to a few hundred grams, or an ATEX machine room is needed. B2L (ammonia) requires a separate machine room, detectors and emergency ventilation. Our refrigerant chart lists the safety class, GWP and field of use of every refrigerant.