N95 masks can be recycled for a second time if they are not used for 4 hours. In general, N95 masks are not worn continuously for more than 4 hours, and if they are not contaminated or wet, you can hang them in a ventilated, dry place, and they can be recycled for a second time. N95 masks are generally replaced every 4 hours.N95 masks is the filtration efficiency of 95%, if more than 4 hours, some microbial strains of particulate matter will block the mask’s filtration layer, affecting the filtering effect of the mask. Due to the higher price of N95 masks, if the protective effect is better, you can still extend the use of time appropriately. It is recommended to replace the mask once every 4 hours, which can better prevent bacteria from invading and maintain health.