These filters are made of 5 layers (2 layers of melt-blown fabric, 2 layers of non-woven fabric, 1 layer of activated carbon filter). They have a filtration capacity of 98.2% on fine particles of 2.5 μm. Viruses are usually transmitted through the air by micro-droplets - microscopic particles less than 5 μm in size. Not washable, the use of these filters varies from 4 hours to several days depending on the intensity of their use. If the filter is wet, it should be replaced.