Gas Networks Ireland (GNI) is focused on converting to a decarbonised network by displacing natural gas with hydrogen to realise a net zero integrated energy system through targeted deployment at scale. Converting a natural gas network to allow any percentage hydrogen requires several technical, regulatory, and operational barriers to be overcome. Hydrogen has a minimum ignition energy (MIE) that is an order of magnitude lower than that of natural gas which is a concern in relation to leaks and atmospheric vents. Regarding the existing GNI transmission network, entirely composed of steel pipelines, the severity of the embrittlement mechanism, hydrogen-enhanced fatigue, depends on the pressure, the fatigue loading and the steel grade. In its conversion journey, GNI will conduct material testing and assessment to evaluate the performance of metals, seals, and polymers in the presence of hydrogen, particularly focusing on hydrogen embrittlement and corrosion risks. There is also the matter of an evolving position regarding codes of practice where for example a certain percentage of hydrogen was once thought to be permissible in steel pipelines without adverse effects. This position has since been revised with action required regardless of the blended percentage. Therefore, no allowable hydrogen concentration in volume percentage can be prescribed. An additional consideration is the need for an inspection and maintenance program during the operating phase of the pipeline. GNI pipelines are subject to a statutory Pressure Systems Safety Regulations (PSSR) inspection program. There is likely to be amendments to this once hydrogen enters the pipeline network. In terms of maintenance activities, GNI utilises a prioritisation methodology constructed from both asset and program attributes. This will be impacted by the introduction of hydrogen with modelling and testing required to re-validate the processes.