The only downside of the DIY route is the noise. Most box fans that I've seen are very noisy relative to "real" air cleaners/purifiers. I've used a box fan pl

The only downside of the DIY route is the noise. Most box fans that I've seen are very noisy relative to "real" air cleaners/purifiers. I've used a box fan plus furnace filter for years to deal with cat litter dust. Since the particles I want to filter are quite large, I can get away with using a fairly cheap furnace filter. The nice thing about this is that it's really easy to scale it to your requirements. To deal with the noise, I used a motion sensor and switched outlet to only run it for 10 minutes after the litter has been used. This runs through my existing home automation stuff (Home Assistant+Node-RED), but it could also be done with an Arduino (you don't even something that powerful - two I/O lines is enough), a PIR sensor, and a solid state relay for the fan control. I've tried a number of low-dust/no-dust litters, but most of have lead to the cats finding other places to do their business or have disappeared from store shelves when I've needed to replenish it. Everything about this is a compromise between litter acceptance, litter availability, litter cost, filter cost, filter life, noise, and dust production.