Electrolysers range from small, appliance-size products to large, multi-megawatt-scale production facilities. In all cases quality and safety must be ensured. One of the major concerns when designing, building, operating or even talking about a hydrogen system is safety. Known for its high flammability range and small molecular size, hydrogen can easily leak, forming an explosive mixture if adequate measures are not taken. Taking adequate measures, however, can be a straightforward process if attention is paid to safety from the design on.