Design the smoke detector spacing for a single-storey warehouse: 30 m × 20 m plan area, 9 m clear height, smooth flat ceiling. The facility is classified Ordinary Hazard Group 1 per NFPA 72 (2019 edition). Determine required detector spacing, coverage area per detector, and minimum detector count.
| Room dimensions | 30 m × 20 m (600 m²) |
| Ceiling height | h = 9.0 m |
| Ceiling type | Smooth, flat (no obstructions) |
| Hazard class | Ordinary Hazard Group 1 |
| Standard used | NFPA 72 (2019) |
| Ambient temperature | 20 °C (ordinary) |
| Mounting height | 9.0 m (ceiling mount) |
| Check | Status | Util. | Value |
|---|---|---|---|
| Base spacing — Ordinary Hazard | PASS |
|
S_base = 12.1 m (40 ft) centre-to-centre |
| Height correction (h > 4.3 m) | PASS |
|
k_h = 0.9 — 30% reduction, S_adj = 8.5 m |
| Coverage area per detector | PASS |
|
A_det = 72.3 m² ≤ 80 m² max for 9 m height |
| Minimum detectors required | PASS |
|
N = 9 detectors (3 rows × 3 columns, 8.5 m grid) |
| Spot-type detector spacing | PASS |
|
D_max = 9.2 m between detectors |
| Distance to wall (≤ 0.5 × S) | PASS |
|
max 4.25 m from any wall — compliant |
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