This part of ISO 10993 specifies a method for the determination of allowable limits for substances leachable from medical devices. It is intended for use in deriving standards and estimating appropriate limits where standards do not exist. It describes a systematic process through which identified risks arising from toxicologically hazardous substances present in medical devices can be quantified. This part of ISO 10993 is not applicable to devices that have no patient contact (e.g. in vitro diagnostic devices). Exposure to a particular chemical substance may arise from sources other than the device@ such as food@ water or air. This part of ISO 10993 does not address the potential for exposure from such sources.