During the tapping, refining and casting processes of manganese ferroalloys, there is a considerable amount of fume generated when the high temperature molten metal vaporizes and oxidizes in the air atmosphere. Fume formation is undesired from a work environment perspective and its spreading outside plant premises may be detrimental to local communities. Experimental studies and industrial observations indicate that the fume generated from the casting of ferromanganese (FeMn) alloy can be significantly reduced by increasing the humidity above the molten metal. However, it is also important to understand the effect of water vapour on the fuming rate of silico-manganese (SiMn) alloys. Laboratory scale experiments were carried out by varying the humidity in an impinging air jet blown onto the surface of a SiMn alloy melt. The fuming rate and fume characteristics (composition, morphology) in the wet air experiments were compared with dry air experiments. The fume composition was also thermodynamically simulated for different gas compositions, using FactSage 7.1.