"GB/T 43905.4-2024 Laboratory methods for soot and gas sampling in welding and related processes, Part 4: Limits for welding soot emission from welding materials" specifies the method for preparing limits for soot emission from welding materials during welding, including procedures for determining soot emission rates and chemical composition, test conditions and preparation of test reports. Applicable to arc welding joining or surfacing processes of non-alloy steel, alloy steel and non-ferrous metals, including welding methods such as welding electrode arc welding, gas shielded arc welding and self-shielded arc welding. It aims to regulate the determination and evaluation of welding soot emission, which is of great significance to protect the health and environment of welding operators.