Non-woven medical masks are available in 3 grades with 3 different uses. The outer layer has a waterproof feature, which effectively prevents liquid droplets from being splashed out when the patient sneezes, coughs, breathes hard … The outer surface is usually light blue to distinguish it. or a certain color (other than white) to identify.
The inner layer is always white, very different from the outer layer. The surface of the fabric turning inwards is close to the skin of the face, so it must be pure and smooth, free of ruffled fibers, not uncomfortable. In addition, the innermost layer should have water permeability to absorb sweat, creating comfort for users.
The middle layer prevents droplets from filtering and filters out dust and bacteria. It can be said that this is the class that determines the quality of a 3-layer medical mask. The «right» filter layer must allow air to pass easily, creating a sense of ventilation for the user but must have a tight structure sufficient to filter out extremely small particles or bacteria.
Corona virus is about 150-200 nm (nanometer) and influenza Influenza A is 80-120nm, these viruses mainly reside in large drops of saliva. According to a 2013 study: large droplets of saliva are usually 75-360 micrometers (1 micrometre = 1,000 nanometers), so these saliva droplets can easily be trapped by conventional medical masks. often with the ability to effectively filter particles larger than 5 micrometers.
Currently, Covid-19 has been causing extremely dangerous acute pneumonia epidemic. Many people have chosen to protect themselves by wearing medical masks. However, wearing a face mask right for the mask to promote the maximum effect.