This standard provides requirements for the design, installation, functioning, maintenance, and testing of gaseous fire extinguishing systems using HCFC-125 as the extinguishant. It is intended for total flooding systems protecting enclosed hazards, focusing on agent concentration, safety for personnel, and system integrity.
Gaseous Fire Extinguishing Systems - HCFC-125 Extinguishing Systems
Quick Reference Values
NOAEL (No Observable Adverse Effect Level)7.5% by volume
LOAEL (Lowest Observable Adverse Effect Level)10.0% by volume
Minimum Design Concentration for Class A (Surface Fire)8.0% by volume
Minimum Design Concentration for Class B (Heptane)8.7% by volume
Typical Cylinder Storage Pressure25 bar or 42 bar at 21°C
Minimum Agent Hold Time10 minutes
Maximum Discharge Time10 seconds for 95% of minimum design quantity
Key Formulas
W = (V/s) * [c / (100 - c)] — Formula for calculating weight of extinguishing agent
Practical Notes
Room integrity is critical. A Door Fan Test as per Annex E is mandatory to ensure the enclosure can hold the required gas concentration for at least 10 minutes.
HCFC-125 is an ozone-depleting substance with high global warming potential, and its use is being phased down under international agreements. Consider modern alternatives like inert gases (IG-55, IG-100) or chemical agents with lower environmental impact (e.g., FK-5-1-12).
For normally occupied areas, the design concentration must not exceed the NOAEL of 7.5%. If it does, strict safety measures including lock-out valves and time delays are mandatory.