Statistics, lessons learned and recommendations from analysis of HIAD 2.0 database

The manuscript firstly describes the data collection and validation process for the European Hydrogen Incidents and Accidents Database (HIAD 2.0), a public repository tool collecting systematic data on hydrogen-related incidents and near-misses. This is followed by an overview of HIAD 2.0, which currently contains 706 events. Subsequently, the approaches and procedures followed by the authors to derive lessons learned and formulate recommendations from the events are described. The lessons learned have been divided into four categories including system design; system manufacturing, installation and modification; human factors and emergency response. An overarching lesson learned is that minor events which occurred simultaneously could still result in serious consequences, echoing James Reason's Swiss Cheese theory. Recommendations were formulated in relation to the established safety principles adapted for hydrogen by the European Hydrogen Safety Panel, considering operational modes, industrial sectors, and human factors. This workprovide an important contribution to the safety of systems involving hydrogen, benefitting technical safety engineers, emergency responders and emergency services. The lesson learned and the discussion derived from the statistics can also be used in training and risk assessment studies, being of equal importance to promote and assist the development of sound safety culture in organisations.