A Model of Hydrogen Ignition Probability based on Leak Data from Hydrogen Filling Stations

The probability of ignition of hydrogen leaks is one of the main uncertainties when analysing the risks of hydrogen infrastructure. Several ignition probability models are available, but they are mainly based on judgement and give widely differing results.
To develop an improved model, this paper collects available data on 168 leaks from hydrogen filling stations (HFS) and tube trailer transfer at similar facilities, using incident reports collected from public domain sources. The dataset is dominated by leaks in Japan and the USA, and has only one leak in China and none at all in Germany and South Korea, despite these countries all having large HFS populations. Although there are differences between the data from different countries, the study maximises the dataset by combining all available data.
A new ignition probability model (HFS-2024) is based on this dataset, expressing ignition probability as a function of the hydrogen release rate. The confidence ranges of the data quantify the uncertainty in the new model, as well as validating some previous models in specific release rate ranges, but HFS-2024 provides the best fit to the data over the whole release rate range.
The paper discusses the limitations in the work, which illustrate the need for better data on both ignited and unignited hydrogen leaks. The new approach provides a pathway for updating the model as experience with hydrogen leaks is accumulated.

Keywords: Risk assessment, Hydrogen filling stations, Ignition probabilities.