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Engineering ToolBox > Velocities in Ventilation Ducts
The duct velocity in air condition and ventilation systems should not exceed certain limits to avoid unnecessary noise generation and pressure drop in the duct work.
The limits of velocities depends on the actual application. The background noise in an industrial building is significant higher than the noise in a public building and more duct generated noise can be accepted.
Commonly accepted duct velocities can be found in the table below.
| Service | Velocity - v | |||
| 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 |