This document identifies the quality-related responsibilities and tasks included in the supervision of activities related to the welding of products and semi-finished products made of thermoplastic materials and provides guidelines to ensure the quality of the supervision. The fundamental aspects of this document are the following: definition of tasks and responsibilities; definition of the required knowledge, skills and competence. The plastic welding supervisor (PWS) is employed by the organization involved in the welding activities. This document applies to all thermoplastic welding processes.