Abstract
Hydrogen is widely considered a key energy carrier for net-zero targets, particularly in hard-to-abate sectors, yet its small size and high diffusivity make it prone to leakage across the value chain, raising safety, energy-loss, and climate concerns. This review treats hydrogen leakage as an infrastructure-management problem linking leak pathways, detection capability, climate-relevant accounting, and mitigation. Rather than treating reported values as directly comparable leakage rates, we classify the evidence by system boundary and measurement basis, distinguishing physical leakage from broader operational losses. We synthesize advances in acoustic, optical, and catalytic detection, some reaching parts-per-billion sensitivity; atmospheric-chemistry ensembles assess hydrogen’s indirect global warming potential and its dependence on leakage rate, production pathway, and time horizon. We assess mitigation through barrier coatings, sealing materials, and modular design and identify key gaps in leakage quantification, soil-sink uncertainty, long-term material performance, and leakage-specific regulation.