What is meant by "saturated steam"?

Saturated steam refers to steam that exists in equilibrium with its liquid phase at a specific pressure and temperature. This means that at this state, any addition of heat will not increase the temperature of the steam further; rather, it will convert the liquid water into vapor. Saturated steam is characterized by having a particular temperature associated with the pressure it is under, which can be found on steam tables.

When steam is in this saturated condition, it is at the precise point where it can either become superheated if additional heat is added, or condense back into water if heat is removed. This characteristic is crucial in many applications, such as steam heating systems and industrial processes, where the properties of steam must be carefully controlled.

In contrast, steam that has been superheated has more heat than it would at its saturation point and thus is not in equilibrium with its liquid state. Steam produced at atmospheric pressure can indeed be saturated, but it is not exclusively defined by that pressure; steam can be saturated at various pressures. Lastly, steam that contains non-condensable gases would not represent the pure state of saturated steam, as the presence of those gases affects the steam's properties and the equilibrium present in a saturated mixture.