Any cooling fan, as well as any objects that it cools, will invariably become choked with fine dust after a time. But this seems quite surprising considering that all the dust is being accumulated on surfaces that are exposed to large currents of moving air. I've learned of two possible reasons: 1) The boundary layer of air attached to the surface does not move and all dust can easily collect there. 2) Static charge on the surfaces will hold dust. Reason #2 does not seem plausible because dust can collect on grounded heat sinks in computers. I suppose that the true reason is #1. Any comments? Whatever the reason, there seems no way to prevent it other than filtering the air.