KF94 is not for medical standard, the letter KF94 mask stands for Korean standard, the letter 94 stands for protection level, for 0.4μm diameter particles filtration rate is more than 94%, suitable for heavy air pollution, virus rampant environment. The 1st and 2nd layers are non-woven fabrics, which block outside dust, strengthen protection and reduce the risk of infection for users. The 3rd layer is the electrostatic filter layer, which effectively isolates fine dust and harmful allergens. The fourth layer is a skin-friendly layer, which adsorbs moisture generated during breathing to keep the wearer dry and comfortable.