Hydrogen is undoubtely the most talked-about carbon-free energy vector. However, policymakers and citizens that are supporting hydrogen large-scale penetration in the energy sector should not only be aware of the evident benefits but also of potential safety and climatic risks driven by a long term hydrogen-based economy. HYDRA will start from the evaluation of policies and directives on hydrogen technologies to derive the actual penetration rate of H2 in the market, and evaluate atmospheric emissions of hydrogen and other gases linked to production processes or leakages. The project will then model socio-economic and energy scenarios, considering land use and water consumption, due to the future deployment of a hydrogen economy. The possible impact on the atmosphere will be assessed, considering the interaction of H2 with the oxidizing cycles of CH4, CO, N2O, and O3, and the possible increase in water vapor concentrations, finally estimating the overall radiative forcing. HYDRA will also assess the possible contribution of soil in removing H2 from the atmosphere. Climatic projections will simulate possible climate change scenarios caused by the hydrogen economy, to which HYDRA will respond proposing guidlines and mitigation actions. Finally, since hydrogen-air mixes are highly imflammable and H2 leakages can represent a serious safety issue along the whole value chain, HYDRA will develop a remote-control monitoring tool. The HYDRA tool will detect and quantify hydrogen leakages to increase the saefty of hydrogen-based technologies and prevent unecessary emissions to the atmosphere. The monitoring system will also be able to detect emissions of other gases, so that also possible impurities can be taken into account. The monitoring tool will be tested in a facility where a large scale H2 storage infrastructure will be available. Experimental and modeling activities will also be useful to update the LCA methodology in assessing the environmental impact of hydrogen technologies.