Air filter Filter classes Filter classes

| Usage_ | Class_ | Performance | Performance_test | Particulate_size_approaching_100_retention | Test_Standard |
|---|---|---|---|---|---|
| Primary filters | G1 | 65% | Average value | >5µm | BS EN779 |
| Primary filters | G2 | 65–80% | Average value | >5µm | BS EN779 |
| Primary filters | G3 | 80–90% | Average value | >5µm | BS EN779 |
| Primary filters | G4 | 90%– | Average value | >5µm | BS EN779 |
| Secondary filters | F5 | 40–60% | Average value | >5µm | BS EN779 |
| Secondary filters | F6 | 60–80% | Average value | >2µm | BS EN779 |
| Secondary filters | F7 | 80–90% | Average value | >2µm | BS EN779 |
| Secondary filters | F8 | 90–95% | Average value | >1µm | BS EN779 |
| Secondary filters | F9 | 95%– | Average value | >1µm | BS EN779 |
| Semi Hepa | H10 | 85% | Minimum value | >1µm | BS EN1822 |
| Semi Hepa | H11 | 95% | Minimum value | >0.5µm | BS EN1822 |