Wildfire smoke? The Corsi Rosenthal box is better than many HEPA home air filters. And is less than half the price. You can put one together for about $70usd.
https://engineering.ucdavis.edu/news/science-action-how-build-corsi-rosenthal-box
Use the right air filters though
(yes this is a business site, but if you notice the author is Jim Rosenthal.)