HIAD history and what is new in HIAD 2.4
The following timeline provides a historical overview of modifications and the related database versions. Below, we listed the descriptors modified in HIAD 2.2.
The database HIAD was designed in in the frame of the European Network of Excellence and built by JRC. At the end of the HySafe project, JRC has managed, operated and populated HIAD with the support of the International Association HySafe.
HIAD was originally accessible via a web-interface, which enabled online consultation, but had limited data download functions. In 2017, the JRC executed a major upgrade producing HIAD 2.0 with the financial support of the Fuel Cells and Hydrogen 2 Joint Undertaking (FCH2 JU).
In December 2020, HIAD was taken offline due to new IT security requirements. Users could not access anymore directly the data and perform their own search. JRC developed a new sharing system, by exporting the online data into an offline Excel file, to be shared with users. This facilitated users to access and analyse the complete dataset. That file has been requested by and distributed to hundredths of experts.
Since 2022, HIAD is downloadable from the JRC platform of the European Major Accident Hazards Bureau. This platform, managed by JRC, hosted the European database eMARS, HIAD and other safety related tools, including a HIAD dashboard.
In 2026, the Clean Hydrogen Joint Undertaking and JRC brought back HIAD online. It is now also possible to perform customised search online, consult a dashboard providing basic statistics and to download the whole dataset for offline data processing and analysis.
HIAD structure evolution
The following timeline provides an historical overview of modifications and the related HIAD versions. Below the table, we list the database descriptors introduced or modified since HIAD 2.1. HIAD individual data or parameters are called descriptors and are indicated in italics between <> brackets.
- 2007HIAD 1.0
First version in the frame of the Network of Excellence HySafe.
Strongly focused on descriptors serving Quantitative Risk Assessment (QRA) and scenarios for modelling. - 2018HIAD 2.0
Several never-used descriptors were deleted.
Causes and event descriptions were made text fields for a better narrative and analysis.
Quality label descriptor was added. - 2022HIAD 2.1
The causes classification was adopted from the European Hydrogen Safety Panel.
The descriptors summarising the start of the event and its physical effects were modified to describe better the reality.
A new descriptor was added, identifying the stage of the hydrogen supply chain involved. - 2025HIAD 2.2
Improvements on descriptors <Event initiating system> and <Nature of the consequences> were made by adding new values.
New descriptor <Description of the process/facility/unit>.
Distinction between <Lesson learnt> and <Corrective Measures>.
New values for descriptor <Probable ignition source>. - 2026HIAD 2.3
Distinction between root causes and initiating cause, with three new descriptors:
What did fail? Descriptor <Component affected>,
How did it fail? Descriptor <Failure mode>,
Why did it fail? Descriptor <Initiating cause> - 2026HIAD 2.4
Ranges for values adopted for process temperature and pressure.
1. Descriptor <Event initiating system> - It identifies the role played by hydrogen and hydrogen systems during the event. It tells if the event had a hydrogen-system at the start of the sequence of the accidental events. It is important to be able to make this distinction, because otherwise all HIAD events could be wrongly attributed to hydrogen as element starting the sequence of accidental events. In 2025, a new value was added, representing a case in between the two mentioned above, i.e. a case where the hydrogen plays a minor part in the initiation of the event. You can find the new list of values of this descriptor in the Tab ‘Classes for EVENTS’ of the Excel file.
2. Descriptor <Nature of the consequences> - It classifies the consequence of the events. It was originally mainly focused on the difference between hydrogen fire and hydrogen explosion. However, there are many types of events, which do not fall in one of these two categories. Two new values were added to allow for a better description of the reality: ‘explosion followed by fire’ and vice versa. You can find the new list of values of this descriptor in the Tab ‘Classes for EVENTS’ of the Excel file.
3. A new set of descriptors for the initiating factors, addressing the 3 questions: Which component failed? How did it fail? (Failure mode) Why did it fail? (the initiating reason). The set of causes introduced in HIAD 2.1 were not differentiating between initiating causes and root causes. This was limiting the quality of the analysis.
4. Descriptor <Root CAUSE analysis> - It was previously called <Causes comments> and was containing a free text, which had become a container for every type of comments on causes. This descriptor aims now, whenever possible, at making a distinction between the direct or ‘(event) initiating’ cause and root causes. It is often impossible to perform a real root cause analysis, due to lack of details, unless it is not already contained in the primary sources. Nevertheless, it is important to make the mentioned distinction, to avoid the pitfall to attribute all event to a material failure cause, or, at the other extreme, to make management responsible for all.
5. New descriptor <Description of the facility/unit/process/substances> - In HIAD 2.1, the descriptor <Pre-event summary> was containing information on what happened before the start of the incident (if relevant) and on the background processes and facilities. This resulted sometimes in a rather long and crowded descriptor. We have now created a new descriptor dedicated to background information on the processes, plants or operative conditions.
6. Descriptors <Lesson learnt> and <Corrective Measures> - In HIAD 2.1, the descriptor <Lesson Learnt & Corrective Measures> was mixing general lessons learnt, specific recommendations from the post-accidental investigations and inspections, and measures adopted by the operators to avoid the recurrence of the event. JRC has now split the old descriptor in two.
7. Set of descriptors characterising releases – The set of HIAD descriptors characterising gas releases has been largely disregarded by previous event providers. The reason is, on one side, the chronic lack of data, and, on the other side, the vagueness of some of these descriptors. We have now rationalised three old descriptors: <Release type>, <Involved substances> and <Hydrogen released concentration>, by deleting the latter and providing substances and their vol. % (if available) in the second one.
8. Descriptor <Probable ignition source> - In previous versions, this descriptor was a free text, resulting in a list of values overdetailed and lacking coherence. JRC has now adopted a new list of values. Knowing the difficulty to identify an ignition source, we have also adopted the approach to report what the sources claim, avoiding any attempt to rationalise that input. You can find the new list of values in the Tab ‘Classes for EVENT NATURE’ of the Excel file.
9. Descriptor <Date entry in HIAD> - Before 2026, a new version of HIAD with new events was shared once a year. From now on, JRC will be able to add new events to the online version of HIAD along the whole year. To guide the users in identifying the new events, the date of entry is now added to the dataset.
For questions, updates, feedback and collaboration proposal, please write to JRC-PTT-H2SAFETY@ec.europa.eu
