I taught patient care, including the proper USE of a mask. Let’s presume a mask can block 100% of viruses. (which it can’t). Does it KILL the viruses? No. Proper removal of the mask is essential. It must be carefully untiled from the back or the straps can be broken (if disposable). It must be discarded without touching the face of the mask. Otherwise the hands would become contaminated with the viruses. Of course one must never touch the face of the mask once donned. Basically, masks as currently used by the public become fomites and only serve to spread disease. All diseases. they also impair respiration, making us all more sickly and lessening our ability to reason.