As a power provider, hydrogen inspires a great deal of enthusiasm and more than a little wariness. a task addressed security problems related to the usage of hydrogen technologies. Hydrogen fuel cell (HFC) technology will initially be commercialised for market-ready applications such as backup energy supply, portable power generation and powering of materials handling automobiles. These programs generally need, by nature or for safety reasons, that hydrogen systems be used inside. However, current regulations, codes and standards (RCSs) are extremely incomplete regarding the practical requirements of security requirements inside. Addressing the safe indoor usage of HFC systems for early markets had been the primary objective of the project. The project desired to supply scientific and engineering understanding for indicating cost-effective means to control dangers, and to develop state-of-the-art security guidelines. It addressed understanding gaps regarding interior hydrogen accumulation, vented deflagration and under-ventilated jet fire. The created knowledge should be translated into security tips, including modern engineering tools supporting their execution. Recommendations should be developed for advancements in the EU and worldwide RCS frameworks to support the safe introduction of HFC in very early markets. Task partners sought to enhance understanding of hydrogen dispersion and accumulation in confined areas. Work centered on a room-like enclosure of typically a few tens of cubic metres with normal ventilation. Based on current and new analytical and numerical models, partners worked on determining characteristic regimes of hydrogen dispersion. Parameters such as the size of the venting location, the size of the enclosure area and the leak flow rates were taken into account. A number of experiments had been carried out to study vented hydrogen–air deflagrations and the interplay between hydrogen–air and enclosure parameters with respect to overpressure effects. Another task was to perform experimental and numerical studies on hydrogen jet fire characteristics. Focus was placed on parameters such as self-extinction, re-ignition, radiation and flame length from outside hydrogen jet fires. Feasible security methods should be given in a tips document with important rules for indoor hydrogen use in the designs. Additional safety products should be proposed whenever sizing techniques are maybe not enough to respect the safety rules.