Hydrogen safety in process industry: Systematization of past lessons

Interest in hydrogen has grown due to its potential as a green fuel, because hydrogen combustion produces only water. However, hydrogen presents two significant challenges: its wide flammability range (4%-75%) and low ignition energy (0.017 mJ), which make leaks highly flammable, and its small molecular size, which easily penetrates materials, altering their microscopic and macroscopic properties and causing leaks that are difficult to detect, increasing the risk of invisible fires. To manage these risks, many studies simulate hydrogen leakage scenarios to establish accurate safety distances. A thorough understanding of hydrogen leakage behaviour and failure mechanisms is crucial for risk assessment. This study addresses a gap in the existing literature on hydrogen-related events. The aim is to identify the most critical equipment in conditions of hydrogen exposure and material degradation in the process industry, to provide support to inspection and monitoring activities for more effective risk management. The analysis identifies the chemical, petrochemical and manufacturing sectors as the most vulnerable to the effects of hydrogen. Corrosion and hydrogen embrittlement are frequent causes of events, mainly affecting pipelines and often resulting in explosions or fires