Clean Steam
Steam is sometimes classified as clean or pure, with both words having the same meaning. Any contaminants within a steam system will reduce the steam’s purity/cleanliness. Contaminants include water treatment chemicals, suspended solids and dissolved solids.
Reducing the amount of moisture within the steam is the most reliable method of reducing the number of contaminants present in the steam system. Steam with a high dryness fraction, contains less contaminants than steam with a low dryness fraction.
Most industrial processes do not require ultra-pure steam, but some industries -such as the pharmaceutical industry- do. Electric boilers, stainless steel boilers, and deaerators, are steam system components that can be used to improve water purity and thus steam purity. Feeding ultra-pure water to the boiler will also increase steam purity.
Additional Resources
https://invenoeng.com/steam-system-engineering-steam-system-meanings-and-terminology