Out of curiosity, do you feel filtering like this actually prevents anything? I'm not questioning the filters but rather the graveness of the threat in the first place (except for the elderly etc.).
The smoke in SF last year made me sick, and air quality rarely bothers me. It’s not just carbon soot, there are all kinds of cyclic hydrocarbons produced by smoldering green wood. It’s much worse than campfire smoke.
Yes, many healthy people were sick in Seattle last year and they were recommending wearing masks outdoors. Anecdotally, I experienced headaches and sluggishness when I didn't wear a mask.