Which refrigerants are flammable and which are non-flammable?

The line-up

Most of the gases we stock are A1 (R-22, R-410A, R-134a, R-404A, R-407C, R-448A, R-23 and R-508B); R-32, R-1234yf and R-1234ze are the A2Ls in the room, and its rise is why flammability literacy became mainstream trade knowledge (background: the ASHRAE class system).

What "mildly flammable" really means

A2L is a deliberately narrow category: flammable in principle, difficult in practice. R-32 needs a high concentration in air and a substantial ignition source; its flame, once lit, propagates at walking pace (≤10 cm/s by definition) with modest pressure rise. That is categorically different from propane's violent A3 behaviour, and it is why standards allow multi-kilogram A2L charges in split ACs while capping A3 to a few hundred grams. Different, not dismissible: the mitigations in the A2L guide are what keep the risk theoretical.

The A1 trap

The most common safety error in the field is treating A1 as "fireproof". Non-flammable means the gas will not carry a flame. It does not mean a cylinder tolerates heat (pressure rises steeply toward relief conditions), and it does not mean the gas is benign in a flame: halogenated refrigerants passed through brazing torches or open flames decompose into hydrogen fluoride and, for chlorinated fluids, phosgene (mechanism and first-response in flame exposure). Recover before hot work — on every class.

Sourcing note

Flammability class is also an authenticity issue: the documented counterfeit failure mode is flammable hydrocarbon or R-40-contaminated product sold in A1-labelled cylinders — a technician brazing on what the label says is non-flammable gas. Factory-sealed branded cylinders from registered sellers, SDS in hand, is the control (see genuine vs counterfeit and why fakes injure).

Mixed-class fleets: running A1, A2L and A3 side by side

The realistic Indian service operation now touches all three classes in one week — A1 across the legacy and R-410A base, A2L on every new split, A3 in the odd window unit or bar fridge: and the failure mode is not ignorance but habit bleed: A1 practices applied unthinkingly to flammable stock. The clean way to run a mixed fleet: segregate identity first — cylinders stored with flammables grouped and marked (post-2020 livery helps: the red band is the one colour signal that survived the RAL 7044 change); tier the tooling — A2L-rated recovery machine, hoses and detector as the house standard, since A2L-rated gear serves A1 work perfectly while the reverse is non-compliant; make ignition control unconditional — recover before brazing on every class, so the one habit that matters most never depends on remembering which gas is in the circuit; and brief per job, not per year — a thirty-second 'what class is this system' check at job start is the entire administrative burden. Fleet-level, the economics favour standardising on the stricter discipline: one set of habits that is always safe beats two sets applied conditionally, and the incremental cost (a rated detector, rated recovery gear, some signage) is one avoided incident away from free. Class-specific working detail lives in the A2L guide.

Related: A2L handling · Flame exposure · R-32 supply · Is refrigerant toxic?