In contrast to process water, there is no pharmacopoeia standard for water for clean steam purposes (or any type of steam for use in pharmaceutical manufacturing). A specification for the purity of such steam must be prepared by each manufacturer, and the specification must be such that they meet the GMP requirement to avoid contamination of the product. In theory, there could be a wide range of different clean steam specifications, applicable to products of different degrees of purity and different stages of manufacture. In practice, the industry has tended to consolidate around specifications where the steam condensate meets the pharmacopoeia specification for PW or WFI.
Probably the commonest clean steam specification is that the condensate meets WFI requirements for conductivity, TOC and endotoxin (The microbial limit is normally excluded as it is acknowledged that viable microorganisms cannot survive, indeed are killed, in steam systems). The WFI based specification is used where an endotoxin limit is required, and this is important for injectables and parenteral products. These are produced as sterile solutions and, since clean steam is primarily used for sterilization, they make-up the majority of manufacturing facilities where clean steam is used.