You may DIY HEPA air purifier recommended by the Oregon state Health Authority during their 2022 wild fires: h
ttps://youtu.be/EUHVo54tXz0
It is literally a fan and a HEPA filter.
The cube version offers ~4x the airflow, thanks to the larger surface area of filtration; see this from the Idaho Department of Environmental Quality:
https://youtube.com/shorts/UwiV9BDMOnY
Source: KakiDIY Facebook