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Filter Boxes

16 products

Duct mounted filter boxes (filter cassette boxes) for round ventilation ducting. We stock the Systemair FGR and FFR series from 100mm to 400mm, fitted inline to hold a replaceable panel filter that protects fans, heat exchangers and supply air from dust and pollen. FFR boxes come with a BFR-M5 filter included. All genuine Systemair, in UK stock with next working day delivery. Use the buttons below to filter by duct size, or for help choosing the right box or replacement filters email hello@efans.co.uk or call 0161 399 3825.

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Frequently asked questions

What is a duct filter box for?

A filter box sits inline in the ductwork and holds a replaceable filter cassette, cleaning the air passing through. It protects the fan and any downstream heat exchanger or coil from dust build-up and keeps supply air clean, which matters on MVHR, supply and commercial systems.

FGR or FFR, what's the difference?

Both are circular duct mounted filter cassette boxes. The FFR is supplied complete with a BFR-M5 filter ready to run; the FGR is the filter box housing. Choose the size to match your duct diameter, 100mm to 400mm.

Which filter grade and how often do I replace it?

These boxes take BFR panel filters, commonly M5 (medium) grade for general supply and extract; finer grades are available where cleaner air is needed. Replace filters when they discolour or airflow drops, typically every 6 to 12 months depending on the environment. Keep spare BFR filters on hand.

100mm 125mm 150mm 200mm 250mm 315mm 355mm 400mm

Showing 1 - 16 of 16 products

Systemair FGR Filter Cassette Box for ducting, 100mm size, designed for air filtration and ventilation systems.

Systemair FGR Filter Cassette Box for ducting, 100mm size, designed for air filtration and ventilation systems.

Product data sheet

In stock

Next day delivery
available

Systemair

Systemair FGR Filter Cassette Box - 100mm

100mm
Panel filter cassette
G3 filter fitted

In stock

Next day delivery available

£89.99

Systemair FGR Filter Cassette Box for ducting, 125mm size, showing the air filter unit with mounting frame and filter media.

Systemair FGR Filter Cassette Box for ducting, 125mm size, showing the air filter unit with mounting frame and filter media.

Product data sheet

In stock

Next day delivery
available

Systemair

Systemair FGR Filter Cassette Box - 125mm

125mm
Panel filter cassette
G3 filter fitted

In stock

Next day delivery available

£94.99

Systemair FGR Filter Cassette Box for ducting, 150mm size, shown with filter components inside and ventilation fittings.

Systemair FGR Filter Cassette Box for ducting, 150mm size, shown with filter components inside and ventilation fittings.

Product data sheet

In stock

Next day delivery
available

Systemair

Systemair FGR Filter Cassette Box - 150mm

150mm
Panel filter cassette
G3 filter fitted

In stock

Next day delivery available

£98.33

Systemair FGR Filter Cassette Box for ducting, 200mm size, with filtration media visible inside the cassette for HVAC systems.

Systemair FGR Filter Cassette Box for ducting, 200mm size, with filtration media visible inside the cassette for HVAC systems.

Product data sheet

In stock

Next day delivery
available

Systemair

Systemair FGR Filter Cassette Box - 200mm

200mm
Panel filter cassette
G3 filter fitted

In stock

Next day delivery available

£104.99

Systemair FGR Filter Cassette Box for ducting, 250mm size, with metal casing and filter grille for HVAC ventilation systems.

Systemair FGR Filter Cassette Box for ducting, 250mm size, with metal casing and filter grille for HVAC ventilation systems.

Product data sheet

In stock

Next day delivery
available

Systemair

Systemair FGR Filter Cassette Box - 250mm

250mm
Panel filter cassette
G3 filter fitted

In stock

Next day delivery available

£118.99

Systemair FGR Filter Cassette Box for ducting, 315mm size, with filter cassette and metal casing for ventilation systems.

Systemair FGR Filter Cassette Box for ducting, 315mm size, with filter cassette and metal casing for ventilation systems.

Product data sheet

In stock

Next day delivery
available

Systemair

Systemair FGR Filter Cassette Box - 315mm

315mm
Panel filter cassette
G3 filter fitted

In stock

Next day delivery available

£142.99

Systemair FFR duct-mounted circular filter cassette box with BFR-M5 filter, 150mm size, for HVAC air filtration systems.

Systemair FFR duct-mounted circular filter cassette box with BFR-M5 filter, 150mm size, for HVAC air filtration systems.

Product data sheet

In stock

Next day delivery
available

Systemair

Systemair FFR Filter Cassette Box Duct Mounted Circular With BFR-M5 Filter - 150mm

150mm
Bag filter cassette
M5 bag filter included

In stock

Next day delivery available

£163.99

Systemair FFR filter cassette box for duct mounting, circular design with BFR-M5 filter, 125mm size, used in HVAC ventilation systems.

Systemair FFR filter cassette box for duct mounting, circular design with BFR-M5 filter, 125mm size, used in HVAC ventilation systems.

Product data sheet

In stock

Next day delivery
available

Systemair

Systemair FFR Filter Cassette Box Duct Mounted Circular With BFR-M5 Filter - 125mm

125mm
Bag filter cassette
M5 bag filter included

In stock

Next day delivery available

£170.75

Circular duct-mounted Systemair FFR filter cassette with BFR-M5 filter, 100mm size, shown in a technical installation setting.

Circular duct-mounted Systemair FFR filter cassette with BFR-M5 filter, 100mm size, shown in a technical installation setting.

Product data sheet

In stock

Next day delivery
available

Systemair

Systemair FFR Filter Cassette Box Duct Mounted Circular With BFR-M5 Filter - 100mm

100mm
Bag filter cassette
M5 bag filter included

In stock

Next day delivery available

£181.99

Systemair FGR Filter Cassette Box for ducting, 355mm, showing the rectangular filter cassette with filtration media.

Systemair FGR Filter Cassette Box for ducting, 355mm, showing the rectangular filter cassette with filtration media.

Product data sheet

In stock

Next day delivery
available

Systemair

Systemair FGR Filter Cassette Box - 355mm

355mm
Panel filter cassette
G3 filter fitted

In stock

Next day delivery available

£194.66

Systemair FGR filter cassette box for ducting, 400mm size, with visible filter slots and metal casing.

Systemair FGR filter cassette box for ducting, 400mm size, with visible filter slots and metal casing.

Product data sheet

In stock

Next day delivery
available

Systemair

Systemair FGR Filter Cassette Box - 400mm

400mm
Panel filter cassette
G3 filter fitted

In stock

Next day delivery available

£197.99

Systemair FFR filter cassette for duct mounting with circular design and BFR-M5 filter, 200mm size for air filtration.

Systemair FFR filter cassette for duct mounting with circular design and BFR-M5 filter, 200mm size for air filtration.

Product data sheet

In stock

Next day delivery
available

Systemair

Systemair FFR Filter Cassette Box Duct Mounted Circular With BFR-M5 Filter - 200mm

200mm
Bag filter cassette
M5 bag filter included

In stock

Next day delivery available

£206.57

Systemair FFR filter cassette box for duct mounting, circular design with BFR-M5 filter, 250mm size for air filtration.

Systemair FFR filter cassette box for duct mounting, circular design with BFR-M5 filter, 250mm size for air filtration.

Product data sheet

In stock

Next day delivery
available

Systemair

Systemair FFR Filter Cassette Box Duct Mounted Circular With BFR-M5 Filter - 250mm

250mm
Bag filter cassette
M5 bag filter included

In stock

Next day delivery available

£244.99

Systemair FFR filter cassette box for duct mounting, circular design with BFR-M5 filter, 355mm size for HVAC systems.

Systemair FFR filter cassette box for duct mounting, circular design with BFR-M5 filter, 355mm size for HVAC systems.

Product data sheet

In stock

Next day delivery
available

Systemair

Systemair FFR Filter Cassette Box Duct Mounted Circular With BFR-M5 Filter - 355mm

355mm
Bag filter cassette
M5 bag filter included

In stock

Next day delivery available

£255.99

Systemair FFR filter cassette box for duct mounting, circular design with BFR-M5 filter, 315mm diameter, used in ventilation systems.

Systemair FFR filter cassette box for duct mounting, circular design with BFR-M5 filter, 315mm diameter, used in ventilation systems.

Product data sheet

In stock

Next day delivery
available

Systemair

Systemair FFR Filter Cassette Box Duct Mounted Circular With BFR-M5 Filter - 315mm

315mm
Bag filter cassette
M5 bag filter included

In stock

Next day delivery available

£270.55

Systemair FFR filter cassette box for duct mounting with BFR-M5 filter, circular design, 400mm diameter.

Systemair FFR filter cassette box for duct mounting with BFR-M5 filter, circular design, 400mm diameter.

Product data sheet

In stock

Next day delivery
available

Systemair

Systemair FFR Filter Cassette Box Duct Mounted Circular With BFR-M5 Filter - 400mm

400mm
Bag filter cassette
M5 bag filter included

In stock

Next day delivery available

£300.99