Velocities in Ventilation Ducts

Recommended 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.

duct velocity

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

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