Fabric Ducting Shapes

Fabric ducting is available in a range of shapes to suit different situations or aesthetics. Round ducts look great but might take up too much height in a low ceiling office. The better option would be the half-round alternative. Perhaps a server room has so much air and such a small amount of space between servers and ceiling that an ellipse duct (very wide but very shallow) would be a better option.

The application and the circumstances will generally suggest a shape.

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Round shape Prihoda fabric duct

Positive pressure only

Round fabric ducts


Round is the default shape for a fabric duct. It is the most natural and efficient shape for the duct to form, and it’s also the easiest to install. We have several different circular duct options for round ducts as they can change diameter and even change shape part way along if required. There are also several suspension options depending upon how the duct should look if/when deflated.

Half round fabric duct

Half Round

Half-round is an extremely popular shape. It is a very aesthetic option for offices or areas requiring a considered finish. It’s also ideal for low ceiling heights or where Variable Air Volume (VAV) systems are used to supply the air. This option can cope with a significant reduction in pressure without affecting the shape, whereas a round duct would require internal rings.

Quarter round

Quarter round fabric duct requires a wall/ceiling junction or a bulkhead. This duct is most often specified in offices and areas struggling for space.

We can place the inlet spigot in the top or back of the duct so that there is no visible inlet connection, making the whole installation very neat and aesthetic.

Ellipse (segment) shaped fabric duct

Ellipse (Segment)

An ellipse duct is very suitable for locations where ceiling height is at a premium. The air volume and the available height will determine the width of the ellipse. The inlet spigot is usually placed on the top surface of the duct so that it’s not visible once installed.

Prihoda fabric duct for indoor swimming pool


Sector fabric ducting tends to be used in special situations where the angles of the supporting surfaces are not 90°. In all other ways, this duct is, in principle, a quarter round duct.

Over pressure and negative pressure

Rectangular fabric duct for extract applications

Square or Rectangular

Square ducting or rectangular ducting is also possible. We use square ducting exclusively when we specify extract (negative pressure) ducting. In both overpressure and negative pressure, the square duct is held in shape by a rail at each corner and a system of braces and threaded bar.

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