Five years. The full name of "Five Certificates" is "Training Certificate for Safety and Life-saving of Offshore Oil Operation", including life-saving at sea, first aid, fire fighting, boat and raft manipulation and helicopter underwater escape. The certificate obtained through the "Five Small Certificates" training of Tianjin Tanggu Training Center is valid for five years, so the five small certificates of Tanggu Training Center cannot dive for five years. Training is training+training, which enables trainees to master certain skills.