Maybe you keep everything super clean, in boxes that are hermetically sealed, and the filament never sees the light of day until it's hits your print surface. Or maybe you're like me and have your spools all over the place. I reached for one the other day to find it rather dusty. Sounds awful right? I know ... I'm bad. Anyway, I had some sort of dust filter in the filament path on my last little printer and had been searching for the right place to attach a similar thing on the BB. Didn't take long to come up with the plan. Maybe it's useful for you too if you're as messy as I am. https://www.thingiverse.com/thing:2451866 Print. Insert sponge. Drop of oil. Poke a thin hole through the sponge. Fit. Happy to adjust it if someone has an idea. Sponge-fitting is a bit of a chore, so a screw on design for the outer casing could fix that, but it works for now.