Quick answer: FM200 (HFC-227ea) quantity W = (V/s) × (C / (100 - C)), where V is the protected volume, s is the agent specific vapour volume (temperature dependent) and C is the design concentration (typically 7–9% for Class A). The result is the agent mass, which sets the cylinder count.
The formula (NFPA 2001)
W = (V / s) × (C / (100 - C))
V = room volume (m³)
s = 0.1269 + 0.000513 × T (m³/kg, T in °C)
C = design concentration (%) ~7% Class A, higher for othersWorked example
Room 100 m³ at 20 °C, C = 7%: s = 0.1269 + 0.000513×20 = 0.1372. W = (100/0.1372)×(7/93) ≈ 54.8 kg of FM200. Divide by cylinder fill to get the number of cylinders, then check discharge time (≤10 s) and room venting.
Agent quantity, cylinder count and vent size to NFPA 2001. Free tool.
Open the FM200 Calculator →Frequently Asked Questions
What concentration of FM200 is needed?
Design concentration is typically about 7% for Class A surface fires, with higher values for certain fuels. NFPA 2001 requires the design concentration to include a safety factor above the extinguishing concentration.
How fast must FM200 discharge?
NFPA 2001 requires FM200 to discharge and reach design concentration within 10 seconds for halocarbon agents, which drives nozzle and pipe sizing.