There is no significant difference in the protection effect of KN95 and N95 masks. In terms of use time, it is recommended that if used continuously it is best not to exceed 5 hours. After 4-5 hours in general, the mask protection effect has significantly decreased. Of course, in the process of use, if the mask has been wet for various reasons, such as spatter, or because of the hot weather, labor intensity is relatively large, the mask has been wet due to more gas, to be replaced at any time. Because the mask that has been completely wet, its protective effect is very low, so it should be replaced in time. If it is not used continuously, it should be evaluated according to the real use time. For example, it should be replaced after 4-5 hours of continuous work. If it is only used on the way to and from work, the time can be extended, but after each use, it should be taken off with both hands holding the straps on both sides, folded and put in a sealed clean bag. If it has been contaminated, its protective effect can not be guaranteed. Content source: Dr. You Lai