Masks don't work. Period. In fact, masks endanger the user by breathing in one's own exhaled carbon dioxide. This causes acidosis in the blood stream. Any elevated level is dangerous. This damages the heart and other internal organs. Acidosis is also causes cancer. The mask also catches sputum droplets that is filled with excretory microbes. This builds up in the mask only to enter back into the lungs causing and respiratory infection and is transmittable to other people. This is only half of the idiocy of wearing masks. Do NOT wear masks.