Conventional steam contains foreign particles from chemicals, from the metal and from the feed water. Normally this does not cause any problems. But even though the temperatures are high, killing most germs etc., conventional steam cannot be considered 100% clean.
Special high quality steam is used in special applications on hospitals, special institutions, pharmaceutical industry, biochemical industry, food industry etc.
The terms often used for this high quality steam, is clean steam and pure steam.
Clean steam is made in an hygienic environment of stainless steel. It is clean, which means that it does not contain significant amounts of particles with e.g. iron, iron oxide and dirt of any kind. The feed water quality is likewise in an appropriate quality. Application could be food industry, and chemical industry.