Only 15% of hydrogen-related accidents are due to the properties of H2: study
Source：hydrogeninsight
Only a fraction of industrial accidents in which hydrogen is involved are clearly caused by the properties of H2 molecules, according to a new study, which found that the cause of most of such accidents can be traced back to those faced by almost any gas-based system.
Hydrogen’s small molecular size and high diffusivity make it likely to leak, while its low minimum ignition energy (MIE, the energy required to ignite via a spark or discharge) puts it at high risk of explosion when mixed with oxygen. Meanwhile, its tendency to cause embrittlement or corrosion in certain metals increases the chances of materials failure, leading to leaks and explosions.
But researchers from University College London and New York University (NYU) Tandon School of Engineering, consulting more than 700 incidents in the EU’s Hydrogen Incidents and Accidents Database (compiled from global data), found that just 15% of hydrogen-related accidents occurred due to these specific properties.
Instead, around 59% were caused by factors that could affect any system carrying or processing gases, including human error, mechanical failure and design flaws.
The remaining 26% of incidents had insufficient detail to make a determination one way or another, said the study, published in the International Journal of Hydrogen Energy.
Around 7% of total accidents were caused by the behaviour of hydrogen in high-pressure environments (between 200-700 bar). These pressures are required when hydrogen is being used for its energy content, to offset the H2 molecule’s relatively low volumetric energy density. However, compressing hydrogen has the effect of reducing its MIE and broadens its flammability limits, making it more likely to ignite.
A further 5% of incidents were caused by hydrogen-induced corrosion, with hydrogen embrittlement, hydrogen-induced cracking and “high temperature hydrogen attack” (when H2 molecules cause the degradation of carbon-containing metals or alloys under high temperatures) accounting for 1% each.
The researchers defined “hydrogen-specific” accidents as those that could not have occurred in a plant carrying one of any of the following combustible gases: methane, propane, ethylene or gasoline vapour.
But the authors warned that even if hydrogen properties are not the root cause of an industrial accident, the presence of the molecule can seriously exacerbate the impact.
“Of course, in the case of hydrogen, the consequences of a fire or an explosion can be a lot more severe due to the unique combustion properties of this gas,” said the report’s lead author, Augustin Guibaud, assistant professor of mechanical and aerospace engineering at NYU Tandon.
Guibaud cited an explosion at a hydrogen refuelling station in Sandvika, Norway, in 2019, which stemmed from a faulty high-pressure component rather than the specific properties of hydrogen.
However, he said, that incident underscores how “even small mechanical flaws can escalate quickly under hydrogen service conditions”.
“When looking at the root cause of an incident, hydrogen is not inherently more dangerous than other flammable gases used in industry,” he added. “However, the way it interacts with materials and the environment is fundamentally different. The danger comes from misunderstanding those differences.”
Regulators currently adopt a one-size-fits all approach to hydrogen-related safety distances or design codes without scientific basis, he continued.
This leads to overly cautious rules in some instances that slow development and raise costs, and overly permissive rules in others that leave “gaps in protection” — points that the authors say must be addressed as H2 is rolled out beyond controlled industrial environments to public infrastructure such as refuelling stations.
“Our findings highlight where traditional safety practices fail to capture hydrogen’s unique behaviour,” he said.
“If we can distinguish between what is general and what is hydrogen-specific, we can focus regulation and design standards on the right problems.”