How many times can the chemical oxygen self rescuer be used?

I believe that for the chemical oxygen self rescuer, besides its quality, customers are most concerned about the use of the chemical oxygen self rescuer. Today, I will introduce how many times the chemical oxygen self rescuer can be used?

Generally speaking, the chemical oxygen self rescuer should be used once as much as possible, because usually the chemical oxygen self rescuer, the medicine in it is a one-time reaction to produce oxygen, so when it is used for the second time, its quantity cannot be guaranteed. Yes, some of them can be used to specify the time of use, such as two hours and three hours, then you have to accurately measure the time you use, so that you may be able to use it again next time.