11 ControlRegulations require that exposure to welding fume andpollutant gases must be prevented, or where this is notreasonably practicable, adequately controlled. The hierarchyof decisions is therefore: Can exposure be prevented? If exposure cannot be prevented, can it be controlled usingmethods other than respiratory protective equipment (RPE)? If RPE is required, what kind?Once a decision has been made tocomplete a joint using welding,complete prevention of exposurebecomes difficult. However, it may bepossible to reduce exposure. One optionis to choose a shielding gas, and perhapseven a welding process, that generateslower emissions. Another is for thewelder to position himself correctly,with his head out of the fume andpaying attention to the direction of anydraught.LEV systems are frequently used onlarge fabrications that are not easilymoved. High-volume / low-velocitysystems with large-diameter trunkingand flanged hoods are preferred.Extracted benches typically take theform of open-fronted boxes, with airextracted through slots or grilles in theback. The workpiece is placed inside thebox for welding, and the fume is carriedaway from the welder in the extractedair. Extracted benches are suitable forIn practice, adequate control of exposure small components that can be handledcan usually be achieved only with themanually.help of ventilation or extraction. TheExtracted booths are similar tochoice of technique depends on theextracted benches, but much larger.circumstances, but the aim is to capture They are used for workpieces that arethe fume at source. This protects nottoo large to fit into an extracted benchonly the welder but also other workers. but that are relatively easy to move.There are four main methods ofremoving fume at source: local exhaustventilation, extracted benches, extractedbooths and "on gun" extraction.Local exhaust ventilation (LEV) isthe most common form of extractionfor welding. It may take the form of aworkshop system with fixed ducting,enabling extraction to be applied at anypoint in the workshop, or mobile unitswith their own filtration systems.40
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