This document specifies a general outline of the ISO3834 series and criteria to be taken into account for the selection of the appropriate level of quality requirements for fusion welding of metallic materials, among the three levels specified in ISO3834-2, ISO3834-3 and ISO3834-4.It is applicable to manufacturing, both in workshops and at field installation sites.This document does not specify requirements for a total quality management system (QMS). However, Clause6 identifies QMS elements where their inclusion complements the ISO3834 series.