Filter system for the product stream or filter for the forced air ventilation (or air handling unit)?
For the product line, we also use as small as technically as possible, so in our set-up, we were able to use 1.5mm filter (SUS) in-line that does not affect really the fouling or clogging. This filter is checked befor and after operation. Should you wish to check it while you are in operation, you may also opt to use pressure gauge and pressure drop will tell you if its clogged or damaged.
For every tipping area, there is also a grid to prevent packaging and cutting tool to go inside the mixer.
As for the forced ventilation, for the room we used EU 4 and EU 7, as for the filler itself, it is fitted with F12 (Hepa filters).
The necessity will be dependent on the hazard and the risk that you will have in the product and how it is filled. If it will be aseptic, then may use up to EU 7 only but with other control elsewhere.