# Sources — A2L Charge Limit Calculator

- **UL 60335-2-40 (concept):** max charge ≈ room volume × LFL × 0.25 safety
  factor. Simplified — real code calculations include additional factors
  (installation height, ventilation, mitigation). Always verify against the
  OEM manual and local code.
- **LFL defaults:** R-454B 0.303 kg/m³, R-32 0.307 kg/m³. Values vary
  slightly by source; the override field accepts the refrigerant's SDS value.
- **Conversions:** 1 ft³ = 0.0283168 m³; 1 kg = 2.20462 lb.