The KF94 mask can filter out at least 94% of particles with a diameter of 0.4μm. The common transmission carrier of the new coronavirus is droplets, which are generally between 1-4μm in diameter, and the mask cannot pass particles with a larger diameter, so wearing the KF94 mask can effectively prevent droplets from coming into direct contact with the human respiratory tract and prevent viral attacks. It should be noted that the KF94 medical series is more effective, while the non-medical series has no requirements for splash-proof ability and bacteria filtration ability. Once contaminated with droplets, there is still a risk of infection if they are not replaced for a long time.