Technical Manual · Fire Safety
Fire Suppression Calculator — Methodology & Formulas
Every input, equation, constant, output, and reference behind the clean-agent fire-suppression calculator. All math is anchored to NFPA 2001 and executed by the deterministic engine js/fire-engine.js against the locked basis-of-design in js/fire-model.js — no back-solved constants, no random values.
01 Purpose & engineering basis
The calculator sizes a total-flooding clean-agent fire-suppression system for a data-hall or electrical room, and screens the space for occupant safety and lithium-ion battery off-gas hazard. It answers four design questions: how much agent is required, is the space safe to occupy at that concentration, how many detectors and cylinders are needed, and does a Li-ion BBU introduce an off-gas hazard the clean agent cannot cover.
Basis of design is user-driven: you supply the room geometry, agent, and (optionally) battery pack; the engine returns a deterministic sizing. The governing authority is NFPA 2001 (2022) Clean Agent Fire Extinguishing Systems, with detection from NFPA 72 and Li-ion hazard from NFPA 855 / UL 9540A:2024.
02 Inputs
Seven inputs across three groups — protected space, clean agent, and an optional lithium-ion BBU panel. Ranges are enforced client-side; blank concentration falls back to the agent Class-A design value.
| Field | Symbol | Unit | Range / default | Meaning |
|---|---|---|---|---|
Room volume inVol | V | m³ | ≥ 1 · default 500 | Net protected volume (deduct solid obstructions; do not deduct racks). |
Floor area inArea | A | m² | ≥ 1 · default 170 | Footprint used for spot-detector coverage. |
Ambient temp inTemp | T | °C | 0–55 · default 20 | Sets specific vapour volume s = k1 + k2·T. |
Clean agent inAgent | — | enum | novec1230 / fm200 / ig541 | Selects the agent property block (halocarbon vs inert path). |
Design conc. inConc | C | % | 1–60 · optional | Design concentration; blank → agent Class-A default (Novec 4.7, FM-200 7.0, IG-541 37.5). |
Battery chemistry inChem | — | enum | '' / nmc / lfp / lco | Optional Li-ion panel; blank disables the off-gas block. |
Pack energy inKwh | E | kWh | ≥ 0 · default 333 | Installed BBU energy driving runaway-heat and off-gas estimates. |
03 Calculation methodology
Two agent-quantity equations (halocarbon vs inert), plus detection, safety, and Li-ion off-gas models. Function names below map one-to-one to js/fire-engine.js.
Halocarbon agent mass — Novec 1230, FM-200
halocarbonAgentKg(V, C, T, k1, k2). NFPA 2001 total-flooding mass equation. k1,k2 per-agent from NFPA 2001 tables.NFPA 2001 · STANDARD
Inert agent volume — IG-541
inertAgentM3(V, C). NFPA 2001 inert-gas volume equation.NFPA 2001 · STANDARD
Cylinders, intensity, GWP, occupant safety
agentForRoom(agent, V, T, C). Design concentration must stay ≤ agent NOAEL for a normally-occupied space.NFPA 2001 A.1.5 · STANDARD
Detection & discharge bands
spotDetectorCount(), dischargeTimeOk(), holdTimeOk().NFPA 72 / 2001 · STANDARD
Lithium-ion off-gas hazard (optional)
liIonRunawayHeatMJ(), liIonOffGasM3(), offGasRoomConcPct(), offGasLflMarginOk().NFPA 855 / UL 9540A · STANDARD
04 Constants & data sources
Every constant lives in the deep-frozen FIRE_MODEL with a // source: tag. Agent property block:
| Agent | Type | k1 | k2 | Class-A C | NOAEL / LOAEL | GWP₁₀₀ |
|---|---|---|---|---|---|---|
| Novec 1230 (FK-5-1-12) | halocarbon | 0.0664 | 0.0002741 | 4.7% | 10.0 / 10.0% | 1 |
| FM-200 (HFC-227ea) | halocarbon | 0.1269 | 0.0005132 | 7.0% | 9.0 / 10.5% | 3220 |
| IG-541 (Inergen) | inert | — | — | 37.5% | 43 / 52% | 0 |
| Li-ion chemistry | Runaway onset | Off-gas | TR heat factor |
|---|---|---|---|
| NMC | 150 °C | 4.0 L/Wh | 2.5 |
| LFP | 166.8 °C | 2.0 L/Wh | 1.2 |
| LCO | 150 °C | 4.5 L/Wh | 2.6 |
Bands: discharge ≤ 10 s (halocarbon), hold ≥ 10 min, spot-detector coverage 84 m², gas-detect alarm at 25% LFL, vent-gas governing LFL 6.0% (H₂ 4.0%). Li-ion onset temperatures from Nature Sci. Reports 2024 via the repo FMECA research doc.
05 Outputs
| Output | Formula | Unit | Interpretation |
|---|---|---|---|
| Agent quantity | W or X | kg / m³ NTP | Total-flooding charge for the space. |
| Design concentration | C | % | Must exceed the agent minimum-extinguish value. |
| Safety margin | NOAEL − C | pts | Green if ≥ 0 (occupiable); negative = re-design. |
| Intensity | W / V | kg/m³ | Charge density, sanity-check vs vendor data. |
| GWP footprint | W · GWP / 1000 | t CO₂e | Halocarbon only; Novec ≈ 0, FM-200 material. |
| Cylinders | ceil(qty / fill) | count | Storage footprint. |
| Spot detectors | ceil(A / 84) | count | NFPA 72 minimum coverage. |
| Discharge time | band | s | ≤ 10 s halocarbon / ≤ 60 s inert. |
| Li-ion runaway heat | E·3.6·f | MJ | Thermal load a clean agent will not absorb. |
| Off-gas vs LFL | offGas/(V+offGas) | vol% | Alarm if > 1.5% (25% of 6% LFL). |
06 Worked example
500 m³ hall, 170 m² floor, 20 °C, Novec 1230 at the 4.7% Class-A default, with a 333 kWh NMC BBU. Numbers reproduce the live engine output exactly.
- Specific vapour volume:
s = 0.0664 + 0.0002741·20 =0.071882 m³/kg - Agent mass:
W = (500 / 0.071882) · (4.7 / 95.3) =343.0 kg - Intensity:
343.0 / 500 =0.686 kg/m³ · GWP footprint343.0·1/1000 =0.34 t CO₂e - Cylinders:
ceil(343.0 / 100) =4 - Safety margin:
10.0 − 4.7 =5.3 pts → occupiable (C ≤ NOAEL) ✓ - Spot detectors:
ceil(170 / 84) =3 · discharge ≤ 10 s ✓ - Li-ion NMC runaway heat:
333·3.6·2.5 =2 997 MJ - Off-gas:
333·4.0 =1 332 m³ → room conc1332/(500+1332)·100 =72.7 vol% → far above 1.5% alarm ⇒ early H₂/CO detection + ventilation mandatory.
07 References & standards
- NFPA 2001 (2022) — Clean Agent Fire Extinguishing Systems: agent mass/volume equations, design concentrations, NOAEL/LOAEL, discharge & hold times, k1/k2 coefficients.
- NFPA 72 — National Fire Alarm & Signaling Code: spot-detector coverage (~84 m²).
- NFPA 855 — Stationary Energy Storage Systems: Li-ion off-gas detection, 25%-LFL alarm.
- UL 9540A:2024 — ESS thermal-runaway fire-propagation test: off-gas basis.
- IEC 62619 — Secondary Li cells for industrial use.
- ISO 14520 / FM Global DS 5-32 — gaseous suppression & data-center protection.
- Engine source —
js/fire-engine.js(FIRE_ENGINE v1.0.0) +js/fire-model.js(FIRE_MODEL, deep-frozen).
08 Assumptions & limitations
Total-flooding, well-mixed enclosure at the stated temperature; cylinder-fill figures are illustrative sizing defaults (tagged ILLUSTRATIVE in the model) and must be confirmed against the chosen vendor's cylinder data. Off-gas volume uses a representative L/Wh per chemistry — a screening estimate, not a substitute for a UL 9540A test report. This manual and the calculator are an engineering education and pre-design aid; final suppression design must be sealed by a qualified fire-protection engineer to the authority having jurisdiction.