The article presents the process of blowing out PET bottles. PET is processed for various applications due to its very good physical properties. In the packaging industry it is used for the production of PET bottles. The concepts of Blow molding is a process used to produce hollow objects from thermoplastic. The basic blow molding process has two fundamental phases. The first phase of the device’s operation consists in heating preforms. The second phase consists in the mechanical extension of the preforms on the axes and on the extension by means of pre-blowing and then blowing the preforms. The discussion was prepared on the basis of the collected literature data.