Classification of Ventilation Dampers

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

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

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

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

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

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:

q_l = q₁₀₀ (dp_l / 100)^1/2 (1)

where

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

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

dp_l = actual pressure drop through the valve (Pa)

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