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Hydrogen is increasingly recognized as a solution for reducing greenhouse gas emissions. While it is primarily produced through thermochemical and electrochemical processes, natural occurrences of hydrogen in the subsurface have been observed worldwide. This suggests the potential for utilizing natural hydrogen as a green energy source. Studies have shown that natural hydrogen is commonly found in Precambrian cratons, ophiolite belts, and mid-oceanic ridges. However, the geological conditions that determine the presence of effective hydrogen systems in the subsurface are still unclear. This paper aims to summarize current knowledge on natural hydrogen generation, discuss critical geological conditions for hydrogen accumulation, and propose possible hydrogen accumulation models for exploration. Two conceptual models are proposed which accommodate different hydrogen generation mechanisms such as serpentinization, radiolysis, and pyrolysis, and offers a framework for guiding future exploration efforts.