I build one during the forest fires earlier in the year, I bought a box fan and 6 Merv 14 furnace filters. My best idea was cutting out the front and back wall

I build one during the forest fires earlier in the year, I bought a box fan and 6 Merv 14 furnace filters. My best idea was cutting out the front and back wall of the box the filters came with and squishing the fan between two. It worked well enough with the 50cm fan that it could make a 10x8m room pleasant in 10 minutes. The only improvement I would make would be buying a lower rated filter for the intake since it got clogged up with a lot of large particles that were kicked up by the fan. I was planning a big build with an impeller fan, but there is something to be said for a solution so stupid that I can rebuild it in 5 minutes with $50 in parts.