Circular ductwork filter boxes — galvanised steel with G4 filter included, Ø100–500 mm

Duct filter boxes are the filtration solution for ventilation installations with circular ductwork — direct mounting on the duct run, without modifying existing AHUs or fans. Unlike cassette filters which require a filter bank in the AHU, the duct filter box installs anywhere on circular ductwork: at the fresh air intake, on the return, at the supply diffuser for a room or any other point in the system.

Construction: galvanised steel casing with circular flanged connections compatible with standard ductwork (dimensions match standard diameters: Ø100, Ø125, Ø150, Ø160, Ø200, Ø250, Ø315, Ø355 mm). Access lid with sealing gaskets for rapid filter replacement without disconnecting the duct. G4 filter included at delivery.

Why G4 on circular ductwork matters: Unfiltered circular ductwork accumulates dust on internal walls within months of operation. Deposited dust becomes a source of bacteria and mould that disperses into the ventilated air. A G4 filter on the supply path stops particles before they enter the duct, reducing internal cleaning frequency from annually to once every few years.

Main applications:

• Supply air filtration in homes with mechanical ventilation systems
• Heat recovery unit protection (extends heat exchanger service life)
• Air filtration into clean rooms or sensitive spaces without a dedicated AHU
• Adding filtration to existing installations without modifying the AHU
• Local filtration on specific system branches

Available sizes: Ø100, Ø125, Ø150, Ø160, Ø200, Ø250, Ø315, Ø500 mm — check existing duct diameter before ordering.

👉 Cassette filters for AHUs 👉 Activated carbon filters for odours