Sulfur oxides (SOx) are a group of chemical compounds composed of sulfur and oxygen. The most common sulfur oxides are sulfur dioxide (SO2) and sulfur trioxide (SO3). Sulfur oxides are produced naturally through volcanic activity and are also released into the atmosphere from human activities like burning fossil fuels and industrial processes.Lower sulfur oxides (SnO, S7O2 and S6O2) Sulfur monoxide (SO) and its dimer, disulfur dioxide (S2O2) Sulfur dioxide (SO2) Sulfur trioxide (SO3) Higher sulfur oxides (SO3, SO4, and polymeric condensates of them) Disulfur monoxide (S2O)