FM200 Clean Agent Estimator: engineer's guide
FM200 mass is determined by protected volume, design concentration, and altitude-corrected specific vapour volume.
Open the FM200 Clean Agent Estimator →
What this calculator does
The calculator returns required agent mass and cylinder count for the protected volume at the target concentration (typically 7% class A, 8.5% class B).
Formulas used
- Agent mass:
W = V × (C / (100 - C)) / s - Specific vapour volume:
s = 0.1269 + 0.000513 × T (m³/kg at T °C)
Variables
- V = protected volume, m³
- C = design concentration, % v/v (7% Class A, 8.5% Class B)
- s = specific vapour volume at ambient temperature
Worked example
Scenario: 150 m³ server room, 20°C, Class A hazard, target 7% concentration.
- s = 0.1269 + 0.000513 × 20 = 0.1372 m³/kg
- W = 150 × (7 / 93) / 0.1372 ≈ 82.3 kg
- Add 5% safety margin → 86.5 kg agent
- Select cylinders 40 kg each → 3 cylinders required
Common mistakes to avoid
- Using 7% for Class B (should be 8.5%)
- Missing altitude correction for high-altitude sites
- Ignoring the 10-minute hold time verification
- Under-sizing for higher-than-design temperature
Frequently asked questions
Room integrity test?
Yes — door fan test to confirm the 10-min retention. Required before commissioning.
Human occupancy limits?
FM200 up to 9% is safe for occupants; above requires immediate evacuation per NFPA 2001.
Standards and references
NFPA 2001, ISO 14520-9, EN 15004-5
Related tools on this site
Open the calculator that pairs with this guide: FM200 Clean Agent Estimator.
Verification note
This guide is planning support only. Final design must be verified against the applicable project specification, authority requirements, manufacturer data, and the standards cited above. Consult a licensed engineer for construction-issue calculations.