Backdraft Damper Duct Manual Volume Damper 6 in - Simple Air Balance

In this review the Therwen 6 in backdraft damper is assessed for homeowners and installers who need a simple, durable way to balance airflow in residential HVAC and venting runs. The bottom line: it is a no-frills, galvanized manual damper that fits standard 6 in ventilation ducts and gives reliable adjustment for branch balancing. Installers will appreciate the straightforward sleeve design and solid metal build, while anyone seeking precise airtight termination should look elsewhere since this product is intended for airflow regulation, not absolute sealing.

Key Features

• Suitable size: The damper fits 6 in ventilation ducts with one bend end at about 5.87 in and the other at about 6 in, making it a direct replacement for common duct runs.
• Easy to install: The sleeve design allows the unit to be slid into pipe and screwed in place quickly, so a single installer can mount and adjust it without specialized tools.
• Use for air balance: As a manual damper, it lets you regulate airflow at each branch to redirect ventilation where needed and improve system balance.
• Galvanized iron material: The sheet metal construction resists deformation and corrosion, so it holds shape under normal HVAC temperatures and lasts for routine residential use.
• Wide applicability: The damper is suitable for range hoods, dryer vents, exhausts and fans, providing a practical balancing tool across most home and light commercial ducting tasks.

Who It's For

This damper is a good fit for DIYers, HVAC installers, and homeowners who need a simple way to modulate airflow in 6 in duct branches for range hoods, exhaust fans, or dryer vents. It works well when the goal is to shift or reduce flow to specific locations rather than to create a perfect airtight seal.

Those who require a fully sealed backflow prevention device or a factory-calibrated motorized damper should look elsewhere. Also consider a higher-precision balancing damper if you need minute adjustments beyond a manual baffle and locking nut.

Pros & Cons

Pros

• Solid build quality from galvanized iron gives durability and resistance to corrosion in typical installations.
• Good fit for standard 6 in ducts and simple sleeve mounting speeds installation.
• Effective airflow adjustment and an easy-to-adjust baffle with a locking nut help maintain desired balance.
• Versatile for multiple venting applications including range hoods and dryer vents.

Cons

• Not fully sealed; the flap may not close perfectly in every unit, so it is not suitable where air termination or absolute backdraft prevention is required.

Specifications

Product type	Manual volume damper with sleeve
Compatible duct diameter	6 in (bend end about 5.87 in)
Height	About 6.25 in
Material	Galvanized iron sheet metal
Applications	Range hoods, dryer vents, exhausts, fans, HVAC branch balancing
Included quantity	2 pcs

Our Verdict

The Therwen 6 in backdraft damper is a practical, value-oriented choice for anyone who needs to balance airflow in 6 in duct branches without fuss. It pairs a durable galvanized sleeve with an adjustable baffle that most DIYers and technicians will find reliable, but it should not be relied on where a fully sealed backdraft barrier is required.

Frequently Asked Questions

Will this fit my 6 in duct?
Yes, the damper is sized for 6 in ventilation ducting with one bend end about 5.87 in and slides into the pipe sleeve for a snug mechanical fit.

Is the damper airtight?
No, it is intended for air balancing and is not a complete airtight termination; sealing with tape or pipe sealant is recommended to reduce leakage.

Can it be used on range hoods and dryer vents?
Yes, the galvanized construction and sleeve design make it suitable for range hoods, dryer vents, exhausts and similar HVAC applications.