Abstract
The nature, source and consequences of the presence of Non Condensable Gases (NCG's) in the steam supply of a porous load steam sterilizer are discussed. Two methods for the introduction of NCG's into a sterilizer steam supply are described. Two methods for monitoring the level of NCG in a sterilizer steam supply are evaluated and the relationship between them outlined. The consequences of underestimating the levels of NCG by the method prescribed in European Standard EN 285 and the advantages of using an in line instrument providing continuous measurement of levels are discussed. The effect of increasing levels of NCG in steam on the temperature profile within a Bowie and Dick Test (BDT) textile pack when tested in four different types of sterilizer cycle and when using two methods of introduction, is described. The results indicated that the level of NCG measured in the steam supply is proportional to the rate of steam consumption. The results also indicate that the temperature depression created within the centre of a BDT textile pack is proportional to the level of NCG measured in the steam and the type of sterilizer cycle employed.
 

Abstract
Based on the example of a sterilisation process with ethylene oxide in a hospital which was validated according to DIN EN 550, it was revealed that general evaluation of the process is not possible using only microbiological tests. While the microbiological results are suggestive of impeccable sterilisation, considerable deviations from the specifications of the standard were noted on measuring the temperature, pressure and humidity at different locations in the steriliser chamber and in the items being sterilised. As regards the parameter that is most important for microbial kill, i.e. the ethylene oxide concentration, it was demonstrated on using this highly precise measuring method for the first time that the concentration was markedly exceeded at different locations within the chamber.
Described here are the measuring method and the measurement accuracy achieved with it, as well as the procedure adopted for validation of sterilisation processes with ethylene oxide, including the results obtained for the respective example.
The importance of online measurements for validation and parametric release of sterilised medical devices is underlined. Using this measuring system, it has been possible for the first time to meet the general requirements for characterisation of a sterilant as per ISO/FDIS 14937, issue 2000:9 (21) in respect of sterilisation with ethylene oxide.
 

Abstract
This paper presents a novel method of multi-dimensional representation of the parameters pressure, temperature and time. A steam penetration test (Bowie-Dick test) provides no information on the time course. Using a BD datalogger (e.g. ebro Electronic, Ingolstadt, Germany) these parameters of the BD test can be documented; inert gases cannot, however, be documented. Hence any faults that cannot be detected by means of the device documentation alone can be recognised at an early stage.