This European Standard specifies requirements and tests for LTSF sterilizers, which use a mixture of low temperature steam and formaldehyde as sterilizing agent, and which are working below ambient pressure only. These sterilizers are primarily used for the sterilization of heat labile medical devices in health care facilities. This European Standard specifies minimum requirements: for the performance and design of sterilizers to ensure that the process is capable of sterilizing medical devices; for the equipment and controls of these sterilizers necessary for the validation and routine control of the sterilization processes.