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| Service | Public buildings | Industrial plant | ||
|---|---|---|---|---|
| m/s | ft/min | m/s | ft/min | |
| Air intake from outside | 2.5–4.5 | 500–900 | 5–6 | 1000–1200 |
| Heater connection to fan | 3.5–4.5 | 700–900 | 5–7 | 1000–1400 |
| Main supply ducts | 5.0–8.0 | 1000–1500 | 6–12 | 1200–2400 |
| Branch supply ducts | 2.5–3.0 | 500–600 | 4.5–9 | 900–1800 |
| Supply registers and grilles | 1.2–2.3 | 250–450 | 1.5–2.5 | 350–500 |
| Low level supply registers | 0.8–1.2 | 150–250 | — | — |
| Main extract ducts | 4.5–8.0 | 900–1500 | 6–12 | 1200–2400 |
| Branch extract ducts | 2.5–3.0 | 500–600 | 4.5–9 | 900–1800 |
Velocities in natural draught extract systems should be 1–3 m/s (200–600 ft/min).