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 and R-407C); R-32 is the A2L 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