See images below showing how to remove the cover to replace the filters

1. Power the machine OFF from the main switch leaving the sub switch ON.
2. Turn main power switch ON while pressing the Utility/Counter key. Keep holding it till the comes up in Service mode.
3. 04 - Counter / Data
4. 03 - Parts Counter
5. 01 - Special Parts
6. 02 - Waste Toner / Filter
7. 004 Developing Dust Proof Filter/1, move arrow down to highlight
8. Select the "Counter Clear" button to reset the count
9. 005 Developing Dust Proof Filter/2, move arrow down to highlight
10. Select the "Counter Clear" button to reset the count
11. 006 PH Dust Proof Filter, move arrow down to highlight
12. Select the "Counter Clear" button to reset the count
13. Select "Return Button"
14. Exit out of service