Ferromanganese, a ferroalloy with high content of manganese, is made by heating a mixture of the oxides MnO₂ and Fe₂O₃, with carbon in a furnace. They undergo a thermal decomposition reaction. It is used as a deoxidizer for steel.

In Forensic Toxicology: Welding is a common industrial process - so common that up to 2% of the working population in industrialized countries has been engaged in some sort of welding. Although the types of welding are many, it has been estimated that shielded metal arc welding (SMAW), gas metal arc welding (GMAW) on mild steel, stainless steel and aluminum are performed by 70% of welders. Arc welding causes emission of manganese.

Welding may produce fumes and gases hazardous to health. Avoid breathing these fumes and gases. Use adequate ventilation. See ANSI Z49.1-1967, Safety in Welding and Cutting, published by American Welding Society. The type of welding identified in all companies was electric arc welding and 90% was MIG on mild steel. A total of 42 welders were monitored for personal exposure to welding fumes. Nearly 60% were overexposed to manganese and 19% were overexposed to iron. Two welders from two different companies had the two highest manganese exposures. Both had worked in isolated welding stations.