I made a box that you fill with carbon pellets, you mount it with the fan but needs longer screw m3 x 30mm. Still testing it,
UPDATE: I resized the part that we fill with carbon and insert inside the main part. It's now tighter
Go check the filament guide that i design. https://makerworld.com/en/models/165747#profileId-181993
And The dampers https://makerworld.com/en/models/125985#profileId-143913