Thresholds for domino effects and safety distances in the process industry: A review of approaches and regulations

• Definition and approach to the domino effect assessment in EU member states (MS) were analyzed.
• A survey on criteria to identify domino hazard in eight EU MS was carried out.
• Threshold criteria for the assessment of domino scenarios were critically compared.
• Important differences in requirements concerning the domino effect are present in EU MS.
• Agreement on escalation thresholds may improve protection from domino scenarios.

Domino effects resulting in cascading events in the chemical and process industries are well known causes of severe accident scenarios. Although the threats due to domino effects are recognized since at least three decades, this is still a controversial topic when coming to its assessment. A number of different approaches are proposed in technical standards and in the scientific literature. The present contribution aims at providing a critical revision of the procedure for the identification of domino effect scenarios. An overview of current regulations for domino effect assessment is provided. The criteria resulting from the regulations are compared and discussed in the light of recent developments concerning escalation hazards and safety distance assessments.