The units have paper filters on them and they have said that the very high static pressure means that laptops designed around them could start using external filters without hampering the performance like they would on existing laptop cooling solutions.

The LTT video quoted something like a 5+ year service life for the filters. That could probably be extended with disassembly and cleaning or potentially by replacing the filters which seem to basically just be a sticker that goes on top of the unit.

In Linus' video it was said that it reverses flow for a second to remove the dust from the filters