How long can KN95 protective masks last?

KN95 protective masks cannot be used repeatedly. Generally, they need to be replaced in about 4 hours. The time is different according to the different environments in which they are used. 

KN95 protective mask is a mask produced in our country that meets the international N95 standard. Wearing this mask can filter more than 95% of non-oily particles. Even in an ordinary outdoor environment or a closed indoor environment without viruses or microorganisms, this type of mask cannot be used repeatedly. Because the filtering function is declining over time, especially when entering and exiting some high-risk fields, such as: hospitals, wards, fever clinics; crowded occasions, such as hotels or some public places, theaters, etc. , This mask needs to be replaced every 4 hours. If splashing or pollution occurs, you need to change the mask at any time.