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Cleanroom Air Distribution Systems
Backdraft Damper
A gravity-closing blade assembly that opens with forward fan pressure and closes when airflow stops to limit reverse movement through the duct.
- Automatic Gravity Closure
- Low-Mass Aluminum Blades
- Adjustable Start-Open Balance
- Forward-Flow Only Protection
Product Introduction
The backdraft damper is a vertically mounted rectangular frame containing horizontally pivoted aluminum blades. Forward differential pressure lifts the blades open; when the fan stops or pressure reverses, gravity returns them to the closed position. Offset pivots and optional counterweights allow the start-open pressure to be adjusted without a motor. Blade-edge and jamb seals reduce reverse leakage, while external counterweight arms remain accessible for final balancing after installation.
Key Features
Gravity-assisted closure blocks reverse flow when the connected fan is idle or wind pressure changes direction.
Adjustable counterweights tune the opening threshold for the installed airflow and blade orientation.
Drainable frame profiles and corrosion-resistant aluminum suit intake, exhaust and weather-exposed openings.
Customer Product Concerns
A backdraft damper must open at the available fan pressure, close reliably at zero flow and remain stable rather than fluttering in a turbulent opening.
Heavy blades consume too much fan pressure before the damper begins to open.Low-mass aluminum blades and an adjustable counterbalance reduce the required start-open differential.
Wind drives outdoor air backward through an idle exhaust branch.Gravity closure and blade-edge seals oppose reverse pressure when forward airflow disappears.
Turbulent fan discharge causes the blades to chatter against their stops.Adequate separation from the fan, balanced blade mass and optional damping weights stabilize movement.
A horizontal installation prevents gravity from returning the blades correctly.The damper orientation and airflow direction are selected so blade weight acts toward the specified closed position.
Typical Applications
Cleanroom exhaust fan outletsOutside-air intake isolationRelief-air discharge openingsRoof and sidewall fan connectionsStandby fan backflow prevention
Technical Parameters
Typical construction ranges for a vertical-mount aluminum backdraft damper are listed below.
| Core Material | Extruded aluminum gravity blades with aluminum frame, stainless pivots and optional elastomer seals |
|---|---|
| Panel Thickness | 1.0–1.5 mm hollow or formed aluminum blade wall |
| Effective Width | 150–1200 mm nominal clear opening width |
| Maximum Length | Up to 1500 mm nominal frame height |
| Steel Facing Thickness | 1.0–1.5 mm galvanized linkage and counterweight support plates |
| Core Density | Approximately 2700 kg/m³ for the aluminum blades and frame |
| Thermal Conductivity | Approximately 160–205 W/(m·K) for aluminum airflow components |
| Surface Finish | Natural mill-finish aluminum or clear anodized and powder-coated construction |
| Joint Type | Flanged rectangular frame with independently pivoted gravity blades and adjustable external counterweights |
| Customization | Available based on the intended application and operating environment. |
Available Options
Blade and jamb sealsAdjustable counterbalance weightsBird screen or weather louver combinationAluminum, galvanized or stainless-steel construction
Planning a Backdraft Damper specification?
Send us your dimensions, installation conditions, performance targets and required surface finish.
