Filter classes: converting EN 779 to ISO 16890
A quick conversion table between the legacy European filter class system (G2–F9) and the current international standard ISO 16890, used today to classify filters for ventilation and air conditioning systems.
Since December 2016, ISO 16890 has progressively replaced the earlier European standard EN 779:2012, which sorted filters into groups G1–G4, M5–M6 and F7–F9. Instead of rating a filter against a single 0.4-micron test particle, the new standard measures capture efficiency across the full particle-size spectrum — the PM1, PM2,5 and PM10 fractions — matching the way pollution is actually distributed in outdoor air.
In practice, both labeling systems still coexist: filter cartridge labels, older HVAC design documentation and supplier quotes commonly show the legacy G/M/F class alongside the newer ePM rating. The table below is a quick reference for sourcing, cross-checking, or replacing filters between the two systems.
Filter class conversion table
Values show the minimum guaranteed capture efficiency for the corresponding particle fraction under ISO 16890.
| Filter class per EN 779 | Filter class per ISO 16890 |
|---|---|
| G2 | ISO Coarse > 30% |
| G3 | ISO Coarse > 45% |
| G4 | ISO Coarse > 60% |
| M5 | ePM10 ≥ 50% |
| M6 | ePM2.5 ≥ 50% |
| F7 | ePM1 ≥ 50% |
| F8 | ePM1 ≥ 70% |
| F9 | ePM1 ≥ 80% |
What each rating means
Coarse dust filter. Captures larger particles above roughly 10 microns — typically used as a pre-filter protecting finer stages and the AHU itself.
Medium filter class. Rated on the particle fraction up to 10 microns (ePM10) — a suitable second filtration stage.
Fine filter. Rated on the smallest fraction, ePM1 (up to 1 micron) — the particles that penetrate deepest into the respiratory system.
The percentage of particles captured within that size fraction — the higher the percentage, the more effective the filtration of fine dust.
Why the conversion matters when buying filters
When requesting quotes for replacement filter cartridges, comparing supplier offers, or reviewing older HVAC design documentation, it's worth knowing that the same letter rating (say, F7) doesn't necessarily mean the same real-world ISO 16890 efficiency across two manufacturers — it depends on the specific filter media. Eurovent recommendation 4/23 (2022) sets out the minimum recommended ePM class by application type (offices, healthcare, industrial facilities, cleanrooms) and is a solid starting point when sourcing a replacement for an older filter.
Frequently asked questions
Is the EN 779 rating still valid?
EN 779 has been formally superseded by ISO 16890, but manufacturers and suppliers still list the legacy G/M/F class as an approximate equivalent alongside the new ePM rating, since it's still referenced in the design documentation of older installations.
What's the difference between ePM1, ePM2.5 and ePM10?
These are three different particle-size fractions used to measure capture efficiency. ePM1 rates the smallest, hardest-to-capture particles (up to 1 micron), ePM2.5 a mid-range fraction, and ePM10 coarser particles. A filter can be rated for one fraction or several at once.
Which filter class should I choose for a typical office space?
For general indoor office environments, Eurovent's recommendation usually points to a class equivalent to ePM2.5 or ePM1 (formerly F7–F8), depending on local outdoor air quality and the specifier's requirements.