1 IntroductionWelding, and other hot processessuch as flame and plasma cutting andspraying, generates fume that can beharmful to health. Air pollution fromwelding has two main constituents:particulate fume and pollutant gases.Both can be hazardous to healthwhen inhaled, but they have differentcharacteristics and so are treatedseparately here.toxicity of fumes generated includethe material being welded, the weldingprocess and the welding parameters,especially current and voltage. The needto maximise welding productivity andminimise costs means that many ofthese parameters may be fixed, and it isunfortunate that the most productivewelding techniques often create themost pollutants.Most countries have specific health andsafety regulations to reduce and controlpeople's exposure to welding emissions.These regulations are generally basedon the airborne concentrations belowwhich the health hazards from thesubstances in question are consideredto be acceptable. These exposure limitsmay be measured in ppm, mg/m³ orother units, they may be averaged overa reference period or given as maximumacceptable concentrations, and theyhave different names in differentcountries - but the goal of keepingexposure within safe limits is common.However, with an understanding ofhow fumes are generated it is oftenpossible to reduce pollution withoutaffecting productivity, even when thematerial to be welded and the weldingprocess are fixed. To control toxic gases,especially carbon monoxide and ozone,the choice of shielding gas can beimportant. To reduce particulate fume,the most important parameter is thechoice of consumable.How easy it is to keep below theexposure limits depends on thechemical species present, theirconcentrations and the duration ofexposure. The most stringent controlsare needed for emissions containinghigh concentrations of componentswith low exposure limits.The best ways to control fume are togenerate less of them, and to changetheir composition to make them lesstoxic. Secondary methods of controlinclude fume extraction systems andpersonal protective equipment.Factors affecting the amount and the4
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