Accidents involving dangerous substances still happen and establishing an effective proactive methodology to provide safe daily operation remains a challenge. Findings about the limitations of the existing approaches with scenario presentation for the purpose of demonstrating that appropriate precautionary actions are taken to ensure a high level of protection, are the basis for the development of the new methodology, presented in this paper. The emphasis of the methodology is on effective daily operation, based on the identification of latent weaknesses; it takes into account that with dynamic processes safety changes from one moment to another. With the new approach, operators are encouraged to think continuously about the issues that have an impact on safety. Another challenge is the fact that understanding what effective daily operation means may differ from country to country and from legislation level to the operator. The guidance in this paper illustrates what effective daily operation means. The assessment of effective daily operation is also used as the risk acceptance criteria for Seveso establishments, and the presented approach is one of methodological guidance on how to implement the Article 19 of the Directive, 2012/18/EU of the European Parliament and of the Council (the Seveso III Directive). (C) 2016 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.