Recommended Air Velocities in Ducts

Ducts and recommended air velocities

Air flow velocity in ducts should be kept within certain limits to avoid noise and unacceptable friction loss and energy consumption.

Low and Medium Pressure Ducts

  • Maximum friction rate 0.1 - 0.2 inches W.G./100 ft
  • Velocity 1,500 - 2,000 ft/min (8 - 10 m/s)
Air Flow RateMaximum Velocity
(m3/h)(CFM)(m/s)(ft/min)
< 300 < 175 2.5 490
< 1,000 < 590 3 590
< 2,000 < 1,200 4 785
< 4,000 < 2,350 5 980
< 10,000 < 5,900 6 1,180
> 10,000 > 5,900 7 1,380

High Pressure Ducts

  • Maximum friction rate less than 0.4 inches W.G./100 ft
  • Velocity 2,000 - 3,500 ft/min (10 - 18 m/s)

Shafts

Air Flow RateMaximum Velocity
(m3/h)(CFM)(m/s)(ft/min)
< 5,000 < 2,950 12 2,350
< 10,000 < 5,900 15 2,950
< 17,000 < 10,000 17 3,350
< 25,000 < 14,700 20 3,940
< 40,000 < 23,500 22 4,300
< 70,000 < 41,000 25 4,900
< 100,000 < 59,000 30 5,800

It is common to keep main duct velocity above 20 m/s (3940 ft/min).

Corridors

Air Flow RateMaximum Velocity
(m3/h)(CFM)(m/s)(ft/min)
< 5,000 < 2,950 10 2,000
< 10,000 < 5,900 12 2,350
< 17,000 < 10,000 15 2,950
< 25,000 < 14,700 17 3,350
< 40,000 < 23,500 20 3,940

User Areas

  • Offices, receptions, lounges and similar
Air Flow RateMaximum Velocity
(m3/h)(CFM)(m/s)(ft/min)
< 5,000 < 2,950 10 2,000
< 10,000 < 5,900 12 2,350
< 17,000 < 10,000 14 2,750
< 25,000 < 14,700 16 3,150

Related Topics

  • Ventilation - Systems for ventilation and air handling - air change rates, ducts and pressure drops, charts and diagrams and more

Related Documents

Tag Search

  • en: ducts air velocity speed

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