The general non-woven disposable masks made by other companies can’t capture fine particles via their physical structures. Instead, they rely on static electricity. But moisture weakens static electricity. Exposure to moisture in exhaled air neutralizes most static charge and weakens capture performance accordingly. Rather than relying on static electricity, YAMASHIN NANO FILTER™ captures fine particles through structural properties (its high-density structure). That means it retains nearly all of its capture performance even after repeated handwashing.