In the last decade significant concern is growing regarding greenhouse gas emissions, global warming and fuel scarcity. Thus, the need arises to implement a new energy carrier that could provide the same energy value and contribute to reducing carbon dioxide emissions. Hydrogen has the potential to be this energy carrier and is becoming more popular. In the near future hydrogen will be produced in large quantities and will certainly need to be transported for a long distances. Given that the world is moving toward green energy, and in order to shorten the transition period and for economic and safety reasons, the use of the existing natural gas transportation grid is the best option. Since the physical and chemical properties of hydrogen and natural gas are different, the injection of hydrogen into natural gas pipeline grid will engender different hazards that are neither all known nor understood. Hydrogen technology must ensure the same safety level as hydrocarbon technology before authorising the interaction with stakeholders and the public. This paper provides a brief summary of the main known hazards and risks associated with hydrogen injection into a natural gas grid and the latest progress in safety measures, the knowledge gaps and future research.