I hope someone can shed some light on that dust in the meanwhile, i guess it cant be smaller than HEPA, but getting air through HEPA with small PC fans is very hard.
Btw, you seemed almost surprised at the use of calcium chloride, i just wanna double check that i didnt mess up the name terribly somehow ? But in shops i often see those little boxes, inside the box at the top is compartment for tablets and i assumed that was calcium chloride, and then as the air passes through this tablet, as it liquifies, it will drain to the bottom of the box. I even saw some variants with a fan but that is where i found some clear warnings that fan and calcium chloride is not a good combination because of the dust. And that is what got me into wanting to know the size of it to see if filtering it could be a solution.