I normally just use the reusable/washable filter that came with my furnace 13 years ago when we built. For this summer I put in a "merv 13" rated disposable that says it filters smoke. I left myself a note from installer when we moved in saying stay below merv 16.
Just googled merv. It stands for minimum efficiency reporting values. Internet says 17 plus is for commercial systems. And 8 is a standard filter.
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