This guidance material has been prepared by the Safety Regulation Commission to provide guidance for ATM safety regulators and support the implementation of ESARR 5. The main purpose of this document is to provide guidance about the provisions established in ESARR 5 and more specifically in its Section 5 ‘Safety Requirements, sub section 5.3 addressing engineers and technical personnel undertaking operational safety related tasks. Each requirement is illustrated by giving explanatory material that includes a rationale, the most significant implications mainly for Regulator but also sometimes for Provider or Operating Organisation, and information about further development.