10.4 Working with flammable refrigerants (R290 and others)
R290 is propane, the same gas family as LPG. It has excellent efficiency and very low GWP. But a leak can form a burnable mixture with air.
The lower flammability limit (LFL) is the lowest gas-in-air concentration that can burn. For R290 it is about 2.1 % by volume (typical value). Below LFL the mix is too lean to burn.
Propane is heavier than air. Like LPG from a leaking cylinder, it collects at floor level and in pits.
Charge size limits exist in product and installation standards. Indoor parts usually carry small charges; larger charges sit outdoors in monobloc units. Follow the manufacturer's limits.
| Rule | R290 (A3) | R32 (A2L) |
|---|---|---|
| Gas detector | Always, set for hydrocarbons | Always, suitable sensor |
| Tools | Spark-free recovery unit and vacuum pump | Rated for A2L |
| Ventilation | Essential; gas sinks to floor | Essential |
| Brazing | Only after recovery and nitrogen purge | Same |
| Cylinder | Marked for flammable gas, red band or label | Flammable label |
Remember
- Use a calibrated gas detector before and during work.
- No smoking, no open flame, no sparking tools in the work zone.
- Recover and purge with nitrogen before any hot work.
- Store and transport cylinders upright, ventilated, away from heat.
- Respect the manufacturer's charge limits.
With A3 and A2L refrigerants, keep gas below its lower flammable limit and keep every ignition source away.
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