This is a very simple RV DIY project you can do for around $30, or less. Likewise, it works best if your RV has a carpeted ceiling. All you need is a USB fan, a USB battery pack, and some industrial strength velcro.
First, velcro the fan’s stand, with the hook side of the velcro facing away from the fan. This is so the fan can be stuck to the carpeted ceiling. Put a strip of velcro on the USB battery pack. Finaally, stick it to the ceiling.
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You might find a USB fan at Walmart or Target, but if you can’t find one locally, Amazon has them.
You can get something like this inexpensively at Walmart, but Amazon also has a wide selection.