This European Standard specifies the requirements and the relevant tests for automatically controlled sterilizers employing ethylene oxide (EO) gas as the sterilant, either as a pure gas or a mixture with other gases, being used for the sterilization of medical devices and their accessories. This European Standard specifies requirements for ethylene oxide sterilizers (EO-sterilizers) working at super or sub-atmospheric pressure for: - the performance and design of sterilizers to ensure that the process is capable of sterilizing medical devices; - the equipment and controls of these sterilizers necessary for the validation and routine control of the sterilization processes. The test loads described in this European Standard are selected to represent a number of loads for the evaluation of the performance of EO sterilizers for medical devices. However, specific loads may require the use of other test loads. This European Standard does not specify those tests which are necessary to determine the probability of a processed product being sterile, nor the routine quality control tests required prior to release of sterile product. These topics are addressed in prEN ISO 11135:2012. This European Standard does not specify requirements for occupational safety associated with the design and operation of EO sterilization facilities. NOTE 1 For further information on safety, see examples in the Bibliography. National or regional regulations can exist. This European Standard does not cover sterilizers which employ the injection of EO or mixtures containing EO directly into packages or into a flexible chamber. This European Standard is not intended as a checklist for suitability of an existing EO sterilizer when assessing compliance with prEN ISO 11135:2012. This standard is not intended to be applied retrospectively. This European Standard does not cover analytical methods for determining levels of residual EO and/or its reaction products. NOTE 3 For further information see ISO 10993-7.