A Review of Hydrogen Ignition Probability Based on Large-Scale Test Results

Ignition of hydrogen-air mixtures is a topic of significance when it comes to assessing the relative safety of any future energy transition that involves hydrogen. Unlike the widespread, decades-long experience of operating with hydrocarbons, there is often little or no statistically significant data on ignition probabilities with hydrogen. Furthermore, the data that has been collated by various bodies can lack information on the mechanism of ignition. For hydrogen, this is generally accepted to be one of three mechanisms: electrostatic ignition, diffusion ignition or hot-surface ignition. This paper approaches the issue from a different direction where the details of experimental work at DNV Spadeadam over the past 20 years are examined. Of particular interest are experiments where hydrogen has been released and the resulting flammable mixture has not been deliberately actioned. It was possible to examine a total of 1,336 cases where hydrogen was released under experimental conditions, and a total of five non-deliberate ignition events were identified. The few occasions where ignition has occurred without deliberate action are examined, and comparisons with simple ignition models are made.