This photo shows the black very thin plastic type filter that sits facing the fan on a household Hitachi CV-SF8 vacuum cleaner.
This Mesh-Urethane filter really restricts the air flow. Its a bit better when I wash it out under the tap with soap and water but soon seems to clog up again. I find it works quite well if I relace it entirely with a piece of soft tissue toilet paper, and keep changing the paper and all the debris that builds up behind it.
Now the question here is what exactly is this very thin plastic type filter (if indeed it is actually a filter) doing? It's the one on the left in the second photo. It seems to have microscopic slits in its surface, but when I wash it, it wont pass water through it, which surely it would if its some kind of filter? It's a thin flexible piece of plastic sheet, and seems really strong. Almost like a sheet of carbon fibre.