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Gas Concentration Hazard Due to Poor Ventilation During R454B (A2L) Charging

Likely causes

R454B is an A2L mildly flammable refrigerant

Check: LFL 11.3 vol%, ignition point 280°C

What to do: Force ventilate machine room before charging — rate: ≥0.4 m³/min per 1 m² floor area

Gas leaking during charging in enclosed machine room accumulates

Check: reaches explosive concentration

What to do: Maintain continuous ventilation during charging (use portable fan or force exhaust fan)

Technician misunderstands A2L as equivalent to A1 (non-flammable)

Check: works without safety measures

What to do: Install refrigerant gas detector at 30 cm above floor in machine room (alarm at 25% LFL = 2.8 vol%)

Hose disconnection or valve misoperation during charging causes large leak

Check: Inspect with instruments or visually

What to do: Remove all ignition sources from machine room (use explosion-proof temporary lighting, no switch operations during work)

Ignition sources in machine room (sparks, motor arcs, light switches) not removed

Check: Inspect with instruments or visually

What to do: Pressure-test hose connections before starting work (0.5 MPa, 5-minute hold)

Field tip

R454B (GWP 466) vapor is heavier than air and settles near the floor. Install ventilation outlets and gas detectors near floor level.

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