Where is the expiration date of the oxygen mask

Mask instructions or box. According to the query know, respirator mask mask manual or box has a clear identification, the expiration date is 2-3 years. Oxygen mask is a device that transfers oxygen from the storage tank to the human lungs. There are mainly medical oxygen masks, civil aviation oxygen masks and other types of oxygen masks, for assisting in the treatment of disease, the protection of aircrew safety plays an important role.