The SOx detects, similarly to the above, the family of sulfur oxides (SO2, SO3, …).
Typically the sulfur oxides are present in higher concentration when they are used fuels such as coal, brown coal or other heavy fossil fuels. It can also result from specific chemical industrial cycles.
The combustion of wood biomass, in the aspect of the gaseous pollutants, is relatively harmless. However, it is important to take into account the emissions of acid gases, which usually have low concentrations, but can vary substantially depending on the actual type of biomass use.