I’ve bought air filters and detectors to protect against wildfire smoke. “Just open the window” is actually pretty good advice in most (non-wildfire) times. My indoor air quality improves sharply as soon as let in an outdoor breeze.
I installed a whole-house fan [1] when AQI outside is good (especially during fire season) - usually early mornings or late evenings - outside air, despite being somewhat dirty is often better than stale indoor air. We do this every day even when it's cold outside for at least 15m. In summer sometimes we leave on the "low" setting all night instead of running the AC.
