MMA FumeMMA welding of carbon and alloy steels will produce welding fume. Welding fume from MMA welding is predominantly particulate fume and there is normally very little gaseous fume. Most of the fume comes from the consumable electrode. The particulate fume from MMA welding of steel will consist of iron oxide plus small amounts of manganese oxide and oxides of any alloying elements such as nickel or chromium. Additionally, fume from basic electrodes will contain inorganic fluorides, which make the fume more irritating to the respiratory system than fume from rutile electrodes. There will also be present in the fume, oxides and silicates of slag forming elements from the electrode coating, such as titanium, calcium, sodium, and potassium. These are normally treated as an inorganic, inert, fraction, and the composition will depend largely on the type of electrode being used. Cellulosic and basic coated electrode types tend to give more particulate fume than rutile types. As a general rule, as the welding current is increased for a single size of electrode so the fume generation rate will increase. Particulate fume from MMA welding steel is not thought to present a serious hazard to health. However, exposure must be kept below current exposure limits. This may usually be achieved by means of local fume extraction.
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