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Ventilation Dampers - Classification

Dampers in ventilation systems may be classified through function, construction or leakage class.

ventilation damper

Classification by Function

Dampers may be classified according their functional tasks in the ventilation system:

  • adjustment
  • closing, running
  • closing, smoke
  • closing, fire
  • overpressure
  • modulating

Classification by Construction

  • plates
  • membranes

Classification by Leakage Class

  • based on BS EN 1751:1999

The leakage class determines the acceptable air leakage through the damper with a 100 Pa pressure difference.

  • class 0 - No requirements
  • class 1 - less than 0.2 m3/s per m2 valve area
  • class 2 - less than 0.04 m3/s per m2 valve area
  • class 3 - less than 0.008 m3/s per m2 valve area
  • class 4 - less than 0.0015 m3/s per m2 valve area

The air flow rates through the dampers at 100 Pa are in general available from the manufacturers catalogs.

Ventilation Dampers - Classification
1 2 3
Adjustment x
Closing, running x
Closing, smoke x
Closing, fire x
Overpressure x
Modulation x

Calculating Leakage Air Flow Rate through a Closed Damper

The leakage air flow through a closed damper can be calculated if the the difference pressure through the damper and the leakage air flow rate at 100 Pa (manufacturer data) through the damper is known:

ql = q100 (dpl / 100)1/2                           (1)


ql = actual volume flow per m2 valve area (m3/s / m2)

q100 = volume flow at 100 Pa per m2 valve area (m3/s / m2)

dpl = actual pressure drop through the valve (Pa)

Related Topics

  • Ventilation Systems

    Design of systems for ventilation and air handling - air change rates, ducts and pressure drops, charts and diagrams and more.

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