A continuous supply of saturated steam is required for steam sterilization and for humidification in certain EO sterilizers. Too high a level of non condescension gases will prevent the attainment of sterilization; too little moisture carried in suspension may allow the steam to become super heated during expansion into the chamber, while excess moisture may cause damp loads. Where steam systems are either routinely or irregularly shut down, large quantities of air will be present in the distribution system on restarting. It is recommended that in such circumstances a comprehensive and validated venting procedure should be applied and testing for steam quality is appropriate.