The effectiveness of the Nano Med Clean filter against viruses has been confirmed by a certificate (VFE - Viral Filtration Efficiency) respected laboratory Nelson Labs in the USA. It is a thin fabric containing a nanofiber structure. Users can put it in a cloth face mask to protect themselves all day long. It is light and highly breathable, so it makes breathing easier. Compared to other materials, the breathability reaches two hundred liters of air per square meter per second.