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# Ventilation Dampers - Classification

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

### Classification by Function

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

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

• 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
FunctionClass
1 2 3
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)

where

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

## Related Documents

• ### HVAC Dampers - Pressure Loss

Pressure head loss in HVAC dampers.
• ### Ventilation Components - Minor Pressure Loss

Pressure loss in ventilation system components like dampers, filters, heaters, coolers and more.

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## Citation

• The Engineering ToolBox (2003). Ventilation Dampers - Classification. [online] Available at: https://www.engineeringtoolbox.com/ventilation-dampers-d_203.html [Accessed Day Month Year].

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