Un-mask. witnessed a test of surgical masks. Small plaster particles were generated in a room. They were visible as a white dust in the air. A man was properly fitted with a surgical mask and spent a short time in the room. When he came out the mask was removed. A camera was focused on the man’s face. The entire area that had been covered by the mask was coated by the white dust. The camera showed that his nostrils and his mouth had been penetrated by the white dust. The dust particles were measured and found to be around 40 micrometers in diameter. The particles that penetrated the mask were the same diameter.

Covid-19 virus molecules are about 0.1 micrometers in diameter. That is 400 times smaller than the plaster particles that penetrated the mask.