This technical specification describes the importance of the chemical characteristics of steam supplied to steam turbines and the need to prevent corrosion and deposition in steam space, in order to minimize the risk of turbine corrosion failures or loss of efficiency or output. The significance of relevant chemical parameters, mostly related to impurity levels, is discussed in terms of types of plant and chemistry operating regimes. This specification is applicable to turbines of all electrical output rating and any exhaust condition, i.e. condensing or back pressure. However, the range of application in terms of output rating or steam pressure is dictated by economic factors such as the relative cost of monitoring equipment and turbine plant. It is designed for new plant, but may be adapted for use on existing plant.