Design density & area of operation
| Standard | EN 12845 |
| Hazard class | Ordinary Hazard Group 4 (OH4) |
| Density | 5.0 mm/min |
| Area of operation | 360 m² |
Typical occupancies
- Woodworking shops
- Textile mills
- Tobacco processing
What this means for a real project
EN 12845 Ordinary Hazard Group 4 (OH4) 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.