You'd think that cases could do with less dust on the inside, and you'd be right, at least Lian Li thinks so.
What the company just announced is that, from now on, all of its enclosures' fans will have removable and washable air filters.
What is perhaps most relevant is that those filters aren't restricted to just the company's own products.
Instead, they should work just fine with any fan of 140mm or 120mm in diameter.
It should be easy to install the filters, with a simple twist, and can either be acquired along with a chassis (they have been shipping with Lian Li model since September) or as a spare part.
They do seem to have a rather dense mesh design, so air intake may be somewhat lessened, but that shouldn't be an issue if you keep them clean.