I just built a new computer and realized that my three intake fans don't have dust filters. Mainly, I have two questions. 1: Do I need dust filters? 2: If I do, can I use a thin cloth like an old white undershirt?
I have two 135mm front intake fans and one 230mm side intake fan. The front two have a multi-layer mesh-type covering and the side fan has a generic mesh covering.
Filters are great, just remember they too need cleaning and they do reduce airflow to an extent.
Some users just use just no filters and clean the system from time to time. I did that for years. Even with filters, dust will still get in because most computer filters are like a screen and small stuff still finds its way in.
An old shirt would be very restrictive to most computer fans.
I actually cut the screens out of my Fractal Define R2, but my media center being on all the time(clearly not on the ground) gets plenty of dust in the filter. It started without it as well, but I put it back in.
I find that pulling air directly from the bottom of a case, even on a desk, gets much more dust than the front. I do not think dust can be fully avoided. The less air you need to cool a system, the less dust you pull into it