Accidental self-ignition of hydrogen released from pressurized cylinder

Hydrogen is a promising energy carrier with wide-ranging applications, but its safe storage and handling remain critical challenges. This study investigates the conditions that lead to the accidental self- (or spontaneous) ignition of hydrogen during controlled release from a pressurized cylinder. In the experimental setup, a hydrogen cylinder pressurized to 200 bar was penetrated by a bullet to simulate an accidental release. Thermocouples were strategically placed to measure the temperature of the escaping gas, while the event was monitored with high-speed cameras and drones equipped with thermal imaging. Temperature measurements of the escaping gas showed minimal variation. However, ignition was observed a few meters from the release point, a surprising result suggesting the involvement of external factors, such as electrostatic discharge or environmental interactions, rather than direct ignition by hydrogen itself. These findings highlight the complexity of hydrogen behavior during high-pressure releases and underline the need for further research to understand and mitigate such risks. • A hydrogen cloud formed after release from a high-pressure cylinder has been experimentally produced. • The release is not from a nozzle but from a real controlled penetration via shooting, to simulate an accidental release. • Spontaneous ignition can occur several meters away from the point of release. • Thermal imaging was critical for identifying ignition events that were not visible in real-time. • Electrostatic discharge, turbulence, and interactions with structural elements are potential ignition mechanisms.