This European Standard specifies the requirements and the relevant tests for automatically controlled sterilizers employing ethylene oxide gas (EO) as the sterilant, either as a pure gas or a mixture with other gases, being used in healthcare facilities, medical device companies or by contract sterilization companies for the sterilization of medical devices and their accessories. These sterilizers are primarily used for the sterilization of heat labile medical devices. This European Standard specifies requirements for ethylene oxide 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 EN ISO 11135-1. This European standard does not specify requirements for occupational safety associated with the design and operation of ethylene oxide sterilization facilities. NOTE 1 For further information on safety, see examples in the Bibliography. National or regional regulations may also exist. Specifications on safety are addressed in EN 61010-1, EN 61010-2-040 and Directive 94/9/EC (ATEX). are not repeated in this European standard. EN 60204-1 may also give valuable guidance. Planning and design of EO-sterilizers applying to this European Standard should consider the environmental impact from the product during its life cycle. Environmental aspects are addressed in Annex G. This European standard is not intended as a checklist for suitability of an existing ethylene oxide sterilizer when assessing compliance with EN°ISO°11135-1. This European standard does not cover sterilization by introducing ethylene oxide or mixtures containing ethylene oxide directly into individual product packages, as these processes can not be controlled and validated. This European standard does not address the risk analysis to be performed during the design of an EO-steriliser. It is however recognized that this is an essential step in the design of a medical device (see e. g. EN ISO 14971).