In view of its infinite source potential and virtually pollutant-free oxidation properties hydrogen fuel offers the promise of an eventual freedom from energy crisis and environmental degradations. But its temperamental combustion characteristics need some fuel-related safety precautions to be specifically adopted. This paper broadly discusses the unique flammability properties of hydrogen as a fuel with particular emphasis on these properties to engine application. Extensive experimental investigation in IIT, Delhi shows that mixture formation and subsequent fuel induction technique must be appropriately designed to cater to the severe thermal environment in the combustion chamber. Overall system design in respect of flammability limits, minimum ignition energy and diffusivity must also take into account problems of leakage and ventilation. Fuel transfer lines, selection and installation of mechanical components (such as flanges and valves), material selections and piping connections are discussed from safety point of view. Evaluation of the safety hazards under realistic operating conditions show that hydrogen does hardly exhibit any additional risk, as compared to petroleum-based fuels.