| Feature / Parameter | BS EN 12845 (Europe / UK) | NFPA 13 (USA) | Key Differences / Notes |
|---|---|---|---|
| Hazard Classification | OH (Ordinary Hazard) & EH (Extra Hazard), divided into groups I, II, III | Light, Ordinary, Extra Hazard, divided into Groups 1 & 2 | Terminology differs; BS uses numeric groups within OH/EH |
| Sprinkler Spacing (Center-to-Center) | OH: 4.5–6 m; EH: 3–4.5 m | Light: 4.6 m; Ordinary: 4.6–6.1 m; Extra Hazard: 3–4.6 m | Maximum spacing values are similar; slight differences by hazard type |
| Coverage Area per Sprinkler | OH: 20–36 m²; EH: 9–20 m² | Light: 12–20 m²; Ordinary: 16–25 m²; Extra Hazard: 9–20 m² | BS EN 12845 allows slightly larger coverage for certain OH areas |
| Water Density / Flow Rate | Specified per hazard group (OH I-III, EH I-II) | Specified per hazard classification (gpm/ft² or l/min/m²) | Both specify density; units and calculation methods differ |
| Installation Type | Wet pipe, dry pipe, pre-action, deluge | Wet pipe, dry pipe, pre-action, deluge | Similar system types; BS has some European-specific clauses |
| Obstruction / Wall Distance | 0.5–0.75 m from walls or obstructions | 0.15–0.46 m from walls depending on sprinkler type | Narrower spacing near walls in NFPA 13 |
| Maximum Height Between Sprinklers | Up to 45 m for OH/EH, adjusted per group | Typically 18–23 m per floor | BS EN 12845 allows taller single-zone heights; NFPA 13 usually limits per story |
| Design Philosophy | Prescriptive + performance guidance, hazard group tables | Prescriptive, detailed tables for spacing, density, and coverage | NFPA 13 has more detailed tables; BS EN 12845 is slightly more flexible for European buildings |
| Pipe Sizing | Based on pressure loss calculations with specific k-factors | Using pipe schedule or hydraulic calculation methods | NFPA offers both prescriptive and calculative approaches; BS is more calculation-focused |
| Water Supply Duration | 60-90 minutes depending on hazard classification | 60-120 minutes depending on hazard classification | NFPA generally requires longer water supply for high hazard occupancies |
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