# F9 Medium Efficiency Bag Air Filter

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> Last updated: 2026-09-20 16:13:23

F9 pocket filters rated 95%–99%: the last medium-efficiency stage before HEPA in cleanrooms and critical air systems.

An F9 bag filter is the last medium-efficiency stage before HEPA. It sits behind the coarse pre-filter and ahead of the terminal filter, so it carries the fine dust that would otherwise reach the HEPA stage; by this point the visible fraction is already gone and what is left is the fraction that loads a final filter fastest. F9 is rated 95% to 99%, which is why it is the grade written into a cleanroom classification or a sterile production area rather than chosen on budget alone.

The construction is what lets a pocket element hold that grade without a large pressure penalty. The media is sewn into pockets that hang into the airflow, so the velocity through the fibre stays low even at rated volume, where a flat pad of the same face area would work much harder for the same airflow. Pocket count and depth are then the selection variables — three, six or eight pockets on a 287 by 592 or 592 by 592 face — and because F7, F8 and F9 share one frame size, a system can move up a grade later without changing the holding frame.

## Key features

- **Filtration efficiency**: 95% – 99% (EN779 F9, the last medium-efficiency stage before HEPA)
- **Low initial resistance**: 125 – 130 Pa (Measured at rated airflow across the three standard sizes)
- **Large media area**: 2.80 – 5.68 m² (Pocket geometry packs the media into a standard 592 mm frame)
- **Rated airflow**: 1,700 – 3,400 m³/h (Matched to the 3, 6 or 8 pocket version)
- **Pocket count**: 3, 6 or 8 (Scales with the volume the air handling unit actually handles)
- **F7 to F9 in one frame**: Grade upgrade in place (Move up a grade later without touching the holding frame)
- **Final resistance**: 450 Pa (A wide working window from a 125–130 Pa start)
- **Galvanised or aluminium frame**: Rigid pocket header (Header and seams hold pocket spacing so the pockets stay open)

## Specifications

- Filtration grade: F9 (F7 and F8 available in the same frame)
- Efficiency: 95% – 99% (EN779 F9)
- Filter media: Special non-woven synthetic fibre, or glass fibre
- Frame: Galvanised steel or aluminium alloy
- Standard sizes: 287×592×550, 592×592×550 and 592×592×600 mm
- Pocket count: 3, 6, 8
- Media area: 2.80 – 5.68 m²
- Initial resistance: 125 – 130 Pa
- Final resistance: 450 Pa
- Rated airflow: 1,700 – 3,400 m³/h
- Target particles: Medium efficiency duty, upstream of the final filter
- Filter object: Fine dust carried past the coarse pre-filter
- Custom sizes: Available to the holding frame dimension
- Frame material: Galvanised steel or aluminium alloy

## Applications

High-grade Cleanrooms, Ultra-clean Environments, Biopharmaceutical Sterile Areas, Semiconductor Fabrication, Electronics Manufacturing, Hospital Operating Theatres, HVAC Fresh Air Units

## Product Features

- Filter Efficiency: 95%-99%
- Applications: Ultra-clean environments, High-grade cleanrooms, Sterile production zones (biopharmaceuticals), Semiconductor fabrication plants. Optimum filtration for extreme cleanliness requirements.

## Technical Parameter