Round duct reducer AWENTA 125 x 100 mm KO125-29, metal ventilation fitting

Round duct reducer AWENTA 125 x 100 mm KO125-29 is a metal ventilation fitting designed to join two circular ducts of different diameters. The fitting provides a smooth transition between a 125 mm duct and a 100 mm duct, supporting continuous airflow with a compact, rigid connection that is suitable for ductwork in HVAC, exhaust and ventilation systems in both residential and commercial installations.

Advantages

The metal construction offers dimensional stability and resistance to deformation, ensuring a reliable seal and long service life under typical ventilation conditions. The tapered geometry promotes reduced turbulence at the transition point, helping to maintain airflow efficiency and lower pressure loss compared with abrupt junctions. The simple shape and standard diameters make the reducer compatible with common circular duct systems and straightforward to integrate into existing ductwork.

Suitable for

• Connecting 125 mm and 100 mm circular ventilation ducts
• Residential ventilation and bathroom or kitchen exhaust fans
• Small commercial HVAC branch reductions and duct modifications
• Retrofit projects where diameter reduction is required

Key specifications

• Material: metal
• Connection type: circular duct reducer (concentric taper)
• Inlet diameter: 125 mm
• Outlet diameter: 100 mm
• Application: ventilation, exhaust and HVAC ductwork

How to use

Position the reducer so the larger end aligns with the 125 mm duct and the smaller end aligns with the 100 mm duct, ensuring correct orientation for airflow direction. Slide the duct ends onto the reducer until fully seated and secure the joints with appropriate clamps, pop rivets, or self-tapping screws depending on the duct material. Seal the connection using HVAC foil tape or approved duct sealant to prevent air leaks and maintain system efficiency. Verify alignment and clearances before final fastening to avoid stress on adjacent duct sections.

Usage recommendations

For best performance, minimize the number of consecutive reducers and maintain smooth, gradual transitions in the duct system. Regularly inspect joints for corrosion or loosened fasteners in environments with high humidity or aggressive air. Use corrosion-resistant fastening and sealing materials when installing in wet or coastal locations.