Required Fire Flow
ISO method from square footage and exposure.
Example
You enter
- Structure area (ft²) 5000
- Construction class ordinary
- Occupancy factor 1
- Exposure charge X (0 = none; ISO Table 330A) 0
- Communication charge P (0 = none) 0
You get
- Needed fire flow (ISO) 1250 gpm
- Base C 1273 gpm
- Construction factor 1
Checked against published worked examples from: ISO / NFPA 1142 area-based simplified screening (project bundled); Insurance Services Office (ISO).
Details, formula, and sources
Formula or tableISO Needed Fire Flow NFF = Ci × O × [1 + (X + P)] with (X + P) at most 0.60, where Ci = 18 × F × sqrt(A) rounded to 250 gpm, F is the construction-class factor, O the occupancy factor, and X and P the additive exposure and communication charges (0 when none); NFF rounded to 250 gpm below 2,500 and to 500 above, 500 to 12,000 gpm.
Source and editionISO Public Protection Classification: the ISO Guide for Determination of Needed Fire Flow, by name.
Free accessISO PPC documents licensed; the per-class 0.6 / 0.8 / 1.0 / 1.5 F-factor multipliers are reproducible from ISO outreach materials.
What governsEstimate. AHJ and licensed fire protection engineer govern.
API field namesstructure_area_ft2, construction_class, occupancy_factor, exposure_factor, communication_factor, needed_fire_flow_gpm, base_C_gpm, construction_factor
- F / O / X / P tables data/fire/fire-flow-formulas.jsonISO PPC Schedule