Zinc and lead are the two most widely used non-ferrous metals after aluminium and copper as vital materials in everyday life. They are mined and smelted in many countries in both the developed and developing world. Both pyrometallurgical as well as hydrometallurgical methods are used for production of lead zinc depending on the type of raw material used as a charge. In the pyrometallurgical process, ore concentrate containing lead, zinc, or both is fed, in some cases after sintering, into a primary smelter. Lead concentrations can be 50-70%, and the sulfur content of sulfidic ores is in the range of 15-20%. Zinc concentration is in the range of 40-60%, with sulfur content in sulfidic ores in the range of 26-34%. Ores with a mixture of lead and zinc concentrate usually have lower respective metal concentrations. During sintering, a blast of hot air or oxygen is used to oxidize the sulfur present in the feed to sulfur dioxide (SO2). An increasing proportion of the supply of both metals (over 50% for lead and 30% for zinc) is being met by recycling. Consumption is predominantly in industrialised countries but is increasing rapidly in the developed world.