First Defense Nasal Screens are a new revolutionary light weight, non inserted, non intrusive, almost non visible, hypo allergenic, self adhesive screen that covers the nasal passage and filters the air we breathe. As certified testing chart shows FDNS can make a significant difference even at sub micron levels of .1µm with 77% efficiencies and over 92% at 1 µm and over 99% at 10 µm.