 dies after about three days. So you can take, for example, a bag of 10 masks, and let's say you're using it to go to the store. So maybe you go to the store, you wear the mask, or you wear it for some sort of period of time, and then you can put it back in the bag labeled Monday, and the next Monday you could use it. But keep in mind, too, that the masks are respirators, so they have filters in them.