A continuous supply of saturated steam is required for steam sterilization and for humidification in certain EO sterilizers. Too high a level of non-condensable gases will prevent the attainment of sterilizing conditions; too little moisture carried in suspension may allow the steam to become superheated during expansion into the chamber, while excess moisture may cause damp loads.
For all these tests, the steam should be sampled from the steam service pipe to each sterilizer. The measurements are taken during a period of maximum steam demand, when steam is first admitted to the sterilizer chamber.
Superheat test
This test is used to demonstrate that the amount of moisture in suspension with steam from the service supply is sufficient to prevent the steam from becoming superheated during expansion into the chamber.
Dryness test
The accurate measurement of the percentage of moisture content in the steam is difficult, and the traditional methods where constant steam flow is required are not suitable for sterilizers.
This test should be regarded not as measuring the true content of moisture in the steam, but as a method by which the provision of acceptable steam quality can be demonstrated.
Non-condensable gas test
This test is used to demonstrate that the level of non-condensable gases in the steam will not prevent the attainment of sterilization conditions in any part of the load.
HTM 2010 Steam Quality Requirements
Superheat < 250C
Dryness Fraction for Linen Loads > 0.90
Dryness Fraction for Metal Loads > 0.95
Non-condensable Gas < 3.5%
