Masks Are Not Virus Filters.

 Input from a filter designer reported by Andrea Widburg at American Thinker:

"Surgical masks were not designed as filters and were not intended to be used as filters. Surgical masks were designed to be used by surgeons standing face down over an operating table holding a patient with an open wound. The surgeon wearing the mask would be able to talk to others in the room without discharging spittle droplets into the patient's wound. Spittle droplets are large and can cause infection." 

Then a test is described. 40 micrometer white plaster dust was puffed into a room.  A surgically-masked man went in and out briefly and was then checked.  His face behind the mask had white dust.  Virus particles are about one hundred times smaller than those dust particles.

"Surgical masks will not prevent the wearer from inhaling or exhaling viruses or bacteria. They provide absolutely no protection for either the wearer or anyone nearby. They create a very dangerous false sense of security for everyone. They also force the wearer to re-breathe carbon dioxide, which will, over time, reduce the wearer's blood oxygen level. That can become very dangerous, especially for older people."