Static field route #19615

What do I do when a backdraft damper at a louver is installed backward?

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📖 Verified core answer

Backdraft dampers are directional. If the fan closes the blades instead of opening them, pull and reinstall the damper in the correct airflow direction.

Open in Field Rescue Open category

Field verification checklist

Run the fan briefly only if safe and watch blade movement.
Check airflow arrows or hinge direction on the damper frame.
Manually move the blades to make sure they swing freely.
Verify the exhaust direction through the louver sleeve.
Resecure and seal after the blade direction is correct.

Ask foreman

The backdraft damper at [location] appears reversed; the fan flow is closing the blades. I checked blade swing and airflow direction. Do you want me to pull and flip the damper frame?

Text to foreman

Route options

A Correct it only if the fix is within your assignment and approved method.

B Hold and document if it affects water intrusion, weatherproofing, rated assemblies, structural anchorage, controls, TAB, or another trade.

C Bring the foreman/detailer the location, what you checked, and what decision you need before sealing, testing, cover, or startup.

Do not do this

Do not force exhaust through a damper that is being pushed closed by the fan.

Why this matters

A reversed damper can create zero airflow, fan noise, vibration, and failed commissioning.

Final verification

Use this as field training guidance. Final direction still comes from the foreman, approved drawings, project specs, manufacturer installation instructions, employer safety policy, pressure/material schedule, and AHJ/code requirements.

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