Welding screens and curtains: Part 1-the derivation of transmittance requirements

The protection of personnel other than welders in the vicinity of welding arcs by means of transparent screens and curtains needed reassessment given the revision of the international standard. This assessment uses internationally accepted eye and skin hazard analysis methods. To quantify the infrared, ultraviolet, and blue-light irradiances at a distance of at least 1 m, compare with Exposure Limit Values (ELV), and calculate the maximum transmittances to reduce the irradiance to below ELVs. Spectral irradiance data of 196 welding arcs were obtained from the Institut National de Recherche et de Sécurité (INRS, National Research and Safety Institute for the Prevention of Occupational Accidents and Diseases, France) CatRayon 5 UV-VIS-IR and the Institut für Arbeitsschutz der Deutschen Gesetzlichen Unfallversicherung (IFA, Institute for Occupational Safety and Health of the German Social Accident Insurance, Germany) UV-VIS databases. The irradiances (IR, UV, and blue-light) at 1 m from the arc were calculated according to the International Commission on Non-Ionizing Radiation Protection (ICNRP) and European Union Directives and compared with the ELVs to provide the required transmittance. The worst case was used to recommend a maximum transmittance. Few arcs exceeded the IR ELV at 1 m, and beyond 1.3 m, none exceeded the ELV. All arcs exceeded the effective UV ELV, and a maximum effective UV transmittance of 0.002% was required to reduce the effective UV irradiance below the ELV. Eighteen of the arcs did not exceed the blue-light irradiance ELV for small sources. For the remaining 179 arcs, a maximum blue-light transmittance of 3.7% was required to reduce the effective blue-light irradiance below the ELV. Welding curtain standards need not have IR transmittance requirements, but guidance for the use of welding curtains should include that they be located at least 1 m from the arc and that recommendation should accompany the products at the point of sale. A maximum UV transmittance of 0.002%, calculated using the corneal and skin hazard weighting function, is proposed to cover the worst-case arc. A maximum blue-light transmittance, calculated using the blue-light hazard weighting function, of 4% is proposed to cover the worst case and transition from the prevailing standards.