Commercial and residential ductwork rely on inline duct fans, which are cylindrical fans placed in a specific section of ductwork. Inline duct fans save space and stay out of sight in residences and commercial spaces while effectively facilitating airflow in the HVAC system. Different ducts feature different designs, so it’s important to select the right duct fan units for your application.

How Do Duct Fans Work?

Inline duct fans operate using several key components, including:

  • External vents: External vents are either mounted ceiling vents or wall vents, with various options available to ensure compatibility with existing ductwork.
  • Intake vents: The ideal size of the intake vent depends on the ducting’s size. Intake vents serve as the system’s extraction point.
  • Fans: Fans are the main part of your inline fan system, and the right type of fan depends on the size of the duct, size of the room, and intended application.
  • Ducting: Your ducting needs to be straight for optimal performance, and you’ll need to install it with the fan if it isn’t already in place. Ducting connects the motor to the external vent.

Inline duct blowers appear near vents that sit far from the system’s blowing unit. The fan lends mechanical air pull to the designated vent’s ducts, allowing air to flow efficiently throughout the entire system and preventing air from leaving through other vents.

There are two main types of inline duct fans: tube axial direct drive and tube axial belt drive fans. Both of these fans feature a tube-shaped housing, but belt drive fans operate by consuming power via a motor-powered belt, while direct drive fans operate directly through the motor.

Belt drive fans require occasional maintenance for belt replacements or testing for proper belt tension. Direct drive variants require minimal maintenance because of their reliance on fewer components. Applications with large ducting systems that have many bends or require high static pressure tend to use belt-driven fans. Direct drive fans are best for smaller spaces and simpler ductwork.

Benefits of Inline Duct Fans

Inline duct fans offer a few advantages over traditional booster fans, such as:

  • Energy efficiency: Inline duct fans can be installed in areas of high duct losses and improve the efficiency of exhausting operations. They can blow air faster and further than booster fans with similar amounts of energy consumption.
  • Multiple intake points: If a space requires several intake points for ventilation, such as multiple rooms or a single large room, inline duct fans can accommodate it. Using a Y junction, inline fans allow for several inlets or outlets.
  • Reduced noise levels: Noise is immediately noticeable with booster fans, but inline fans operate quietly. This is due to their positioning inside the ducting, which is farther from rooms and vents. If the roofing has sufficient insulation, there is almost no noise.
  • More power: While a 12-inch booster fan normally operates at around 800 cubic feet of air per minute (CFM), an inline duct fan of the same size provides up to 1,500 CFM. Inline duct fans are also available with higher-power motors and in larger sizes.


Several applications benefit from using inline duct fans instead of other systems. These applications include:

  • HVAC systems
  • Fresh air systems
  • Air purification
  • Communications equipment

Inline Duct Fans From Pelonis Technologies

At Pelonis Technologies, we offer innovative inline duct fan products designed for even the most demanding applications, including heating, air conditioning, ventilation, and refrigeration. Our advanced inline duct fans provide superior quality and high performance for a range of cooling applications. Depending on our customers’ needs, we can customize products for specific applications, accommodate multiple configurations, and provide easy installation.

Contact us to learn more about our products, or request a quote to get started on a custom solution for your application.

Let us put our experience and expertise to work.