Refrigerant Safety: Classification, Asphyxiation, Pressure and Decomposition
Classification
ASHRAE 34 / ISO 817 give each refrigerant a toxicity letter (A = lower toxicity, B = higher) and a flammability number (1 = none, 2L = lower flammability, 2, 3 = higher). R-410A, R-134a, R-407C and R-744 are A1; R-32 and R-1234yf are A2L; R-290 propane is A3; ammonia R-717 is B2L. Know where your refrigerant sits before you plan the job.
The four main hazards
Asphyxiation: most halocarbons are heavier than air, so they collect in cellars, pits and plant rooms and displace oxygen with no warning smell. Ammonia, by contrast, is lighter than air and rises. Pressure: R-410A runs roughly 60% higher pressures than R-22, so hoses, gauges and recovery equipment must be rated for it and never mixed with R-22 kit. Cold burns: liquid refrigerant boils at around -40 °C on skin, causing instant frostbite and eye damage. Decomposition: a flame or hot surface on refrigerant produces hydrogen fluoride and carbonyl fluoride, so never braze or solder a charged line.
Traps
- A2L does not mean "will not burn"; treat it as flammable for ignition sources, hot work and charge limits.
- A leak in a basement does not disperse - ventilate and use a calibrated detector before entering.
- Compressed air plus refrigerant and oil can form an explosive mixture; oxygen must never be used for purging or testing.
- Frostbite from a liquid spill is worse under a watch or ring.
Rule of thumb
Any space below ground, without through-ventilation, or with no second exit is treated as a confined space: test the atmosphere, ventilate, and post a second person at the access point before anyone enters.