I wore a navy blue polo yesterday outside for several hours. Wife said, "What is all that on your shirt?" I took a couple of the biggest pieces with a tweezer and put them under my old B&L double-magnifier on my stamp collecting board. The largest piece of ash was 1mm x 2mm irregular square.
That's not to say you're not right, since wildfire particulate matter can actually enter the bloodstream (!), R95 is not going to eliminate all of it.
I suppose it depends on how far you are from the Canadian border. Maybe in Minnesota, Wisconsin, Upstate New York, etc, you are going to get some bigger stuff still floating in the air.
Down a few hundred miles south of the border and I just can’t see it happening.