Backdraft Dampers

backdraft damper, vertical gravity damperBackdraft dampers, or gravity dampers, are integral components of ventilation systems. They are engineered to allow air to flow in one direction while preventing reverse flow.

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They come in different types, such as commercial backdraft dampers and heavy-duty industrial backdraft dampers, and they can function either through gravity or via assistance from springs, weights, or actuators.

Their primary role is facilitating and controlling the directional airflow in various applications, ranging from exhaust systems to solar heating setups.

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The backdraft damper is opened by air pressure differential and closed by gravity.

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Backdraft Dampers in Ventilation Systems

Backdraft dampers serve a critical function in maintaining air quality within industrial and commercial settings. Their primary role is to regulate airflow direction, allowing air to exit while preventing its re-entry.

This feature is essential in preventing the recirculation of potentially contaminated air, thus promoting a healthy and safe environment.

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How Gravity Dampers Operate

Backdraft dampers operate based on the principle of air pressure and flow direction. When the air pressure in the duct or vent system is greater on one side, the damper blades open, allowing the air to flow freely. These blades stay open as long as the air continues to flow in the same direction.

However, when the air pressure balances or reverses, indicating a change in airflow direction, the damper blades automatically close. This closing mechanism is often aided by gravity, but it can also be facilitated by springs, counterbalance weights, or motors, depending on the damper type.

In this way, backdraft dampers prevent the reverse flow of air, which can be crucial in avoiding the backflow of odorous or contaminated air into the system or space.

Types and Functions


Commercial Backdraft Dampers

Used in general ventilation applications, these dampers operate either by gravity or with an actuator. They prevent reverse airflow in scenarios like exhaust, air intake, and various ventilation contexts.

Industrial Backdraft Dampers

Engineered for more demanding industrial environments, these dampers handle higher pressures and velocities, often using externally mounted counterbalance weights. Their application includes blower outlets, duct isolation, and industrial process isolation.

Understanding the Role of Actuators, Springs, and Adjustable Counterbalance Weights

In backdraft dampers, the use of actuators, springs, and adjustable counterbalance weights is crucial for efficient operation:

These devices, often motor-driven, enable the damper to open and close automatically without depending solely on air velocity or pressure. They are especially useful when precise control over the damper operation is required.

Spring-assist dampers employ springs attached to the damper blades, helping them open or close. The tension in these springs can be adjusted to control the force required to move the blades, thereby regulating the damper operation.

These weights provide a more refined means to control the opening pressure of the damper. By adjusting these weights, one can precisely calibrate the pressure at which the damper opens, providing greater control over the airflow.

These mechanisms provide flexibility and precision in controlling the airflow within ventilation systems, ensuring the dampers cater to diverse industrial and commercial requirements.

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Benefits and Considerations when Selecting Backdraft Dampers

When selecting backdraft dampers, there are several benefits and considerations to keep in mind:

Backdraft dampers improve the efficiency of ventilation systems by regulating airflow direction, reducing energy losses caused by reverse airflow.

Compared to control dampers with actuators, backdraft dampers can be more economical per unit while still providing the necessary functionality. This makes them an excellent choice for systems that require one-way airflow.

Backdraft dampers require relatively less maintenance compared to motorized dampers, reducing overall upkeep costs and time.

Available in a range of types, from single-thickness to teardrop blades, backdraft dampers can be selected based on specific project needs and performance requirements.

By preventing reverse airflow, backdraft dampers play a crucial role in maintaining indoor air quality, which can be especially important in environments sensitive to contaminants.

Some backdraft dampers can function in either horizontal or vertical positions, offering flexibility in installation.

Single-thickness or Teardrop blades

Backdraft dampers often employ either single-thickness or teardrop blades, each offering specific benefits:

These are the more conventional type, offering reliable performance for most applications. They’re lightweight, which makes them responsive to changes in airflow pressure.

These blades, with their unique shape, are designed to reduce airflow resistance, thus providing a more efficient operation. They are usually used in applications where minimal pressure drop and maximum airflow are desired.

Both types of blades operate without the need for an actuator, using the force of the airflow itself to open. This results in a more economical, low-maintenance solution for one-way airflow control.

An optional counterweight can be added to assist or resist the opening action, offering further customization based on specific needs.

Aluminum Wall Vent-Reversible Backdraft Dampers

Made from aluminum, these dampers are lightweight and resistant to corrosion, making them ideal for various environments and conditions, including those with high humidity or corrosive elements.

Their design allows for reversible operation, meaning they can control airflow in either direction as needed. This flexibility can be particularly useful in complex ventilation systems where airflow directions might need to change.

These dampers can be installed in either horizontal or vertical orientations, providing additional flexibility in terms of installation and fitting within the existing ventilation infrastructure.

They allow airflow in one direction and prevent it in the opposite direction, improving the overall efficiency of the ventilation system.

Given their features, these dampers are commonly used in wall vents, helping to maintain desired indoor air quality and prevent the entry of outside air when the ventilation system is not in operation.

Butterfly Backdraft Dampers

Characterized by centrally pivoted blades that resemble butterfly wings when opened

Efficiently control one-way airflow, closing tightly to prevent reverse flow

Their design makes them ideal for limited space applications like ductwork and ventilation shafts.

Can be installed in both horizontal and vertical orientations.

Widely used in various ventilation systems for their efficient operation and space-saving design.

Galvanized Wall Vent-Reversible Backdraft Dampers

Constructed from galvanized steel, known for its robustness and resistance to rust and corrosion.

  1. Designed for reversible operation, able to control airflow in both directions as needed.
Can be installed in either vertical or horizontal configurations, offering installation flexibility.

Permits airflow in one direction while preventing reverse airflow, enhancing the efficiency of the ventilation system.

Commonly used in wall vents to maintain indoor air quality and prevent ingress of external air when the system is inactive.

Official Distributor

Backdraft dampers play a crucial role in commercial and industrial ventilation systems, ensuring optimal airflow and preventing reverse airflow.

They come in a variety of types and designs to suit different applications, including commercial, heavy-duty, and special design dampers like aluminum wall vent-reversible, galvanized wall vent-reversible, and butterfly backdraft dampers. The choice of damper should align with your specific needs in terms of airflow control, pressure requirements, and installation environment.

We have over 100 years of experience in the ventilation space, we work with several manufacturers to provide high-quality backdraft dampers. Our team is always ready to assist you in selecting the best damper for your project, answering any questions, and ensuring a smooth purchasing process. 

Contact us today for expert advice and to explore our wide range of backdraft damper options.


A backdraft damper is a device used in ventilation systems. It allows airflow in one direction and prevents reverse airflow, using components like blades that open and close based on the airflow direction.

Backdraft dampers are like little doors placed within your ventilation system’s ductwork.

You’ll often find them near exhaust outlets, sort of like gatekeepers that stop outside air from sneaking back in when your system isn’t running. They’re also common in parts of the system where fresh air gets pulled in, ensuring air comes in but doesn’t escape back out the same way.

If your ventilation is through the roof or the sides of your building, you’ll likely have dampers there to keep the weather from interfering with your air flow.

In bigger systems, they’re also dotted around the ducts inside the building to help control the air flow in different areas.

Finally, in systems like heat exchangers, exhaust systems, or solar heaters, dampers stop the hot air from going back the wrong way. It’s all about putting them where they’re most needed to keep the air flowing in the right direction.

A control damper and a backdraft damper serve different functions in a ventilation system.

A control damper is used to manage the amount and flow direction of air passing through a system. It’s like a valve for your air ducts, allowing more or less air through based on the needs of the system. Control dampers often use a motor or actuator to adjust the damper position.

On the other hand, a backdraft damper is specifically designed to prevent air from flowing back into the system in the wrong direction. Its blades open when air flows in the correct direction and close when the air tries to flow backward. This operation is typically gravity-assisted and doesn’t require an actuator.

So, while both types of dampers are used to regulate airflow, control dampers provide variable control of airflow rates, and backdraft dampers primarily prevent reverse airflow.

A backdraft damper and a gravity damper are the same thing. Both terms refer to a type of damper used in ventilation systems to allow air to flow in one direction only.

The term “gravity damper” comes from the fact that these devices often use the force of gravity to help close the damper and prevent the air from flowing back in the wrong direction when the system is not in operation. When air flows in the intended direction, the damper’s blades open; when the airflow stops or tries to move in the opposite direction, the blades close.

They’re essentially a one-way gate for air in a ventilation system.

Backdraft Damper Manufactures

venco fans manufacturer

Venco Dampers

United Enertech Supplier, united enertech distributor

United Enertech

hartzell industrial fans

Hartzell Fans & Dampers

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Providing Ventilation Equipment to the Following Industries
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