Fourth Edition, December 2023 - This document is a revision of the third edition of this Guideline, dated July 2004 and updated in June 2007. This revision clarifies the description of the method for assessing the in-place cleanability of food processing equipment and includes optimisations of the method without changing the fundamental principles. The optimisations are based on empirical data from testing experience and are intended to improve repeatability and reproducibility to further strengthen the quality assurance of testing for all EHEDG Authorized Testing Laboratories (ATLs).