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
Classification by Construction
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.
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)