The method for combining the numerical gas network simulation with experimentally determined flow characteristics of pipeline ruptures is presented which enables calculation of gas losses from damaged gas networks. Main causes of damages are discussed and the thermodynamics. of gas flow through pipelines, nozzles and irregular openings as well as principles of gas network simulation are described. Flow characteristics of model pipeline damages determined experimentally are presented. The results of combining these results with network simulation are illustrated for sample fragments of distribution network.