Owing to hydrogen properties an uncontrollable leakage and the following ignition of the released hydrogen can lead to dangerous fires or explosions. The paper presents the results of calculations of the size of hazardous zones surrounding broken pipelines transporting hydrogen. The calculations were made for a hole in the pipeline of an equivalent diameter of 5 cm and a complete break of pipelines with diameter of 0.4 m. The impact of pressure in the range from 1 to 10 MPa on the amount of mass outflow of hydrogen, and the effects of such outflow were analysed. The effects of the jet fire and of the explosion of a gas cloud formed of released hydrogen were considered in detail. The range of critical zones in which a damage or destruction of facilities, buildings or other infrastructure components would occur was determined. The size of the zones with a probability of life loss resulting from heat radiation or the pressure wave was estimated using probit functions. At minor breaks of a high-pressure pipeline (hole diameter of 5 cm) from which a jet fire can result, the zone in which the probability of life loss under a 15-second exposure exceeds 50% takes up an area within the radius of approx. 22 m. At a complete break of a pipeline with a diameter of 0.4 m under a 15-second exposure to the arising radiation, the area in which life loss probability is 50% has a radius of 175 m. Under longer exposure to heat radiation, the example values of the radii of hazardous zones which were given above increase to 27 m and 225 m, respectively. If the effect of an uncontrollable gas leakage from the 0.4 m pipeline is a detonation of the formed hydrogen cloud, the hazardous area radius is from 100 m to 170 m, depending on the time needed for the cloud to form. Therefore, it can be assumed that the radii of areas exposed to the adverse effect of radiation and overpressure are of the same order.