Pure Steam Generators

In the operating routine the expressions pure steam as well as clean steam are used repeatedly. It is seldom clear whether the same is meant with these two expressions.

Indeed, it is not really simple to answer this question. The GMP (Good Manufacturing Practices) guidelines very often uses the term 'clean steam' without giving any further explanation. The steam's quality is defined by its use and its quality in turn is regulated in standards and pharmacopoeias. This means that pure steam and clean steam are the same from a pharmaceutical point of view. It was defined in the year 2006 and referred to as pure steam. The quality of this steam is defined by its condensate which must have WFI (Water for Injection) quality. This steam quality is applied for the sterilization of primary packaging material for sterile dosage forms or for the sterilization of equipment parts in contact with the product during sterile production, for example. The term 'clean steam' is quite often used with the same intention but without having its own pharmaceutical definition.

Furthermore, DIN 58950-7 defines a steam quality which is used for the sterilization of goods that are not in direct contact with the product or for the sterilization of closed containers. This steam is called sterilization steam. In contrast to the steam described in the pharmacopoeia the limit for the conductivity of the condensate has a maximum of 10 µm/cm and is above the limit of WFI. But a limit is indicated for the non-condensable gases. The USP also mentions the non-condensable gases but without any specifications. These gases can cause the occurrence of gas bubbles in areas which are difficult to access where they prevent the heating up to the temperature required for sterilization.