Evaluation of the hydrogen explosion hazard

On the basis of brief review of recent experimental and theoretical results an evaluation of hydrogen explosion hazard during accidents is made. It is possible to determine a geometric conditions in which detonation can propagate for a given mixture composition. The main task in this problem is the estimation of detonation cell width for various mixture composition. The direct computer detonation cell modeling instead of ZND-modeling is suggested for this purpose. The conditions of spontaneous detonation or strong explosion processes initiation including deflagration to detonation transition (DDT) and detonation self-initiation mode in nonuniform mixtures (SWACER- mechanism) are analyzed. The detonation self-initiation being considered as part of DDT-process determines the minimum detonation formation distance. The evaluation of this distance in self-initiation mode is suggested for various mixture composition on the basis of the values of minimum initiation energy or detonation cell width. This approach gives a possibility of the hydrogen explosion hazard estimation in spite of many uncertainties remained and important unresolved questions of the DDT and spontaneous detonation