I’ve seen this idea in leeward areas of California wildfire smoke, and while it should work, the caution I would give is to either find a mask which has little air resistance when breathing through it, or to be mindful of that restriction and not try to go all-in on exercise. Masks are breathable and effective at intercepting particulate matter, but I don’t think they’re tested for the sort of heavy, rapid breathing from exercising. And the longevity of the filters under such heavy loads is unclear.

But it’s certainly worth a shot. Just make sure the mask is still snug, since a loose mask will diminish effectiveness.