Start With a Stage Strategy
Most systems run two stages: a cheap primary filter protects a finer final filter, cutting total cost. Clean spaces add a third (HEPA) stage.
Typical Arrangements by Space
| Space / industry | Recommended stages | Notes |
|---|---|---|
| Offices, schools, retail | G4 pre + F7 final | Comfort, moderate IAQ |
| Commercial HVAC (better IAQ) | G4 + F8/F9 | Asthma/allergy, urban |
| Hospital wards | G4 + F8 | Infection control |
| Operating theatres / isolation | G4 + F9 + H13/H14 terminal | ISO 5, laminar |
| Pharma / aseptic | G4 + F8 + H13/H14 | ISO clean |
| Microelectronics cleanroom | G4 + F9 + H14 (+ U15) | Sub-micron control |
| Paint / spray booths | G3/G4 panel + F5-F7 pocket + carbon | Overspray + odour |
| Data centres | G4 pre + F9 final | Low ΔP priority |
| Food & beverage | G4 + F7/F8 | Hygiene, washable frames |
| Compressor / turbine intake | G3/G4 + F6 pocket | Equipment protection |
Quick Rules of Thumb
- Dirty, outdoor or process air first – a robust primary (G3/G4).
- People-sensitive spaces – at least F7 and a planned HEPA for critical zones.
- Odour or VOC complaint – add an activated-carbon stage after particulate filtration.
- Tight energy budget – favour low initial ΔP media and keep the primary stage healthy.
