Built-in filters on box fans are a gimmick. Tape a filter on yourself.

Yes, there are box fans with built-in filters, but they don’t do much for dust. Most of them come with a thin washable pre-filter that’s basically a coarse mesh. It catches pet hair and the occasional dust bunny, but it won’t touch fine dust or allergens.

The real solution is the Corsi-Rosenthal box—just tape a 20x20x1 MERV 13 furnace filter to the back of a normal box fan. That setup is genuinely effective. It moves a lot of air and traps small particles. The built-in “air filter” box fans are just a marketing tweak. They add a crummy filter to a cheap fan and charge you more.