To estimate the risks associated with the use of hydrogen in the distribution network and the built environment compared to the use of natural gas, it is important to know the differences in chances and consequence. The chance relates in particular to the probability of a dangerous situation occurring; the consequences can be expressed in damage caused by that hazardous situation (typically fire or explosion). Mitigating measures are aimed at reducing the chance of a dangerous situation arising or lowering its consequences. To this end, the Hydelta programme defines the 'Hydrogen and Safety' work package in which the main objective is formulated as: Identifying the risks of hydrogen leaks in homes and in the distribution network and defining mitigating measures on the basis of the risks. To answer this main question, this report relies heavily on previously published work from the United Kingdom (UK) where similar research has been conducted. In the first phase of the research, an analysis was made of the work from the UK and a translation was made to the Dutch situation. To give insight in the risks of hydrogen in the English distribution network, a quantitative risk analysis was made (QRA). Supporting experimental research was carried out to improve this QRA model. Based on the results of the model, recommendations have been made for mitigating measures for the UK, that ensure that the risk of the hydrogen infrastructure does not exceed the risks of the current natural gas infrastructure. In the Hydelta work package, the same approach was followed to make an initial assessment of the risks in the Dutch situation. In the first deliverable of the work package, [1] the studies in the UK were analysed and differences with the Dutch situation were identified. Based on this analysis and existing questions about the safety of hydrogen in the built environment from the Dutch grid operators, a start was made in the second phase of the research in the work package with a QRA model for the Dutch (hydrogen) distribution ...