We use fans at our house, and I needed something to be able to help keep them in optimum condition. I made a stiff little brush out of a drinking straw, and now I can use that brush to keep debris from the front and especially the back of the fans.
Source: I have a lot of straws for crafts.
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I let this fan go for far too long before cleaning. See how it collects dust because it runs all the time?
I have a circular fan that works really good when the grates are unblocked. Normally I take the grates off the box fans and clean them with soap and water and then dry them and put them back on.
I use a small, oscillating fan in my kitchen and it seems that overtime the cover gathers a greasy film with dust attached! To quickly and safely clean this off, I unplug the fan and remove the cover.