Design density & area of operation
| Standard | NFPA 13 |
| Hazard class | Ordinary Hazard Group 2 |
| Density | 0.20 gpm/ft² over 1500 ft² |
| Area of operation | 139 m² |
Typical occupancies
- Repair garages
- Machine shops
- Mercantile
What this means for a real project
NFPA 13 Ordinary Hazard Group 2 fixes the pair of numbers — design density and area of operation — that drive the most-remote hydraulic calculation. The pump duty point, riser diameter and pipe schedule all flow from this classification. Pick the wrong class and the entire system is mis-sized.
In FireTwin AI you set the hazard class once per zone; layout, hydraulics and BOM recalculate inline and flag any rule that fails before the design leaves the screen.