We live on a farm, and I bought these for my son to wear over his mouth when he does something really dusty.  These bandanas are so thin that even when folded in half, they don't keep the dust out.  Since they are so thin, they also don't work to wear around your forehead to catch sweat.  I'll send the open pack to Goodwill, but I'm returning the other two.  They aren't good for anything but looks.