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What is a Duct Blower?

B. Turner
B. Turner

A duct blower is a type of supplementary fan used within heating or air conditioning ducts. The blower helps the system move air through the ducts more effectively, which makes it easier for homeowners to maintain the desired temperature in each room. Duct blowers also improve ventilation by moving exhaust air out of the home more quickly. These fans are also known as duct boosters or booster fans.

The basic duct blower consists of an electric motor that is used to turn a series of fan blades. The motor may be wired directly into the home's electrical system or run off a separate battery pack or power supply. These blowers are almost always used in conjunction with larger fan units situated near the home's furnace or air conditioning unit. Some systems may require a series of duct blowers, especially in very large homes.


The primary function of the duct blower is to force heated or conditioned air into hard-to-reach rooms. In some cases, these rooms were added on after the main duct system was designed, making it difficult for air to reach them effectively. In other cases, the home's heating or air conditioning system is not powerful enough to distribute air through the whole house, requiring the use of booster fans. Duct blowers are also used to eliminate stale air, humidity or odors. They are sometimes used in bathrooms or attics as a primary exhaust fan.

Buyers should select duct blowers based on the size and shape of the ductwork. The blower should have the same diameter as the duct, or the same length and width if the ducts are rectangular. While must ducts and related equipment are made of steel, buyers should choose aluminum or stainless steel blowers in areas subject to moisture or corrosive materials.

There are two basic duct blower designs to choose from, including in-line and centrifugal models. In-line units consist of fan blades contained within a metal frame. The frame fits inside the walls of the duct, and air travels perpendicular to the face of the blades. In-line blowers are reversible, but tend to be noisier than other design options.

A centrifugal duct blower consists of blades mounted on the outside of a metal frame, like a paddle wheel on a boat. The blades are oriented along the length of the duct, so that air travels in the same direction as the fan blades. These blowers tend to have smaller blades, which allows them to operate quietly and efficiently but also makes them more susceptible to damage.

Duct blowers improve the overall effectiveness of a heating and cooling system, and allow homeowners to maintain comfort levels without adjusting the thermostat. They may also allow users to buy smaller furnaces or air conditioners, which can reduce equipment costs. By using a smaller heating or cooling system, homeowners can improve energy efficiency levels and even reduce monthly operating expenses.

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