Summarize this article:

Use a handheld vacuum to suck up dust particles on the outer section, or inlet ribs, of the box fan. You can also use a feather duster to wipe away dust or dirt. Make sure the fan is unplugged before cleaning, and don’t use any water on the outer ribs. Wipe away tough dirt spots with a clean cloth. To remove your fan’s grill, follow the instructions related to the specific model of Vornado box fan. You will most likely need to remove screws around the grill and release the grill clips. You can find instructions on how to remove the grill in your owner’s manual or online. Once the grill has been properly removed, you can dust it using a cloth or feather duster. If you’d rather wash it, it's okay to use water on the grill. Use dish soap and water to get rid of any dust and dirt particles. Never put the grill in the dishwasher to prevent it from warping due to the heat. To clean the blades, use a soft cloth dampened with plain water to wipe off any dust particles. Using water on the blades is okay, just make sure to dry them off. If your fan was in a greasy environment like a kitchen, you can use a mild soap to wash the blades. Once all of the pieces have dried off, reassemble the fan by screwing the grill back into place using the screws you took out. If you need help, refer to the fan's instruction manual. Make sure the blades and grill are completely dry before reattaching the pieces and plugging the fan into an outlet.

Summary:
Use a handheld vacuum or feather duster for general cleaning. Remove the grill to clean the fan thoroughly. Clean the grill by dusting it or washing it with dish soap. Wipe down the blades using a damp cloth. Put the fan back together once it's completely dry.