Abstarct: Natural gas passes through various pipeline networks to reach consumers. Natural gas is transmitted through the main lines that formed the transmission pipeline networks (TPNs) to the city's gate, then distributed through the distribution pipeline networks (DPNs) to consumers which includes household, industrial and specific consumer. The DPN consists of a variety of components including natural gas demands, nodes, pipelines and town border stations (TBS). DPNs is designed in a steady state, but the conditions of these networks in the transient conditions are very important for natural gas companies and these conditions should be considered. In the transient conditions and at certain times, a situation occurs for DPNs where the natural gas consumption will increase dramatically at the pipeline network’s nodes. This mode is known as critical condition in DPNs. The severe decrease in ambient temperature and rupture of pipeline network are the most important factors in the increase of natural gas consumptions and as a result, these factors are the most important factors in creating critical conditions in these types of networks. The purpose of this research is to analyze natural gas DPNs in critical conditions. For this purpose, the DPNs are initially examined in a steady state and the temperature, pressure and natural gas flow rate in all nodes and network pipelines are calculated. Then, a method for modeling the DPNs in the transient condition is presented and then using the two important networks, the proposed method is validated. The validation results show that the proposed method has acceptable accuracy. In addition, two natural gas DPNs have been studied in transient conditions. For the boundary conditions of the networks, the case study data (Semnan city) has been selected and natural gas consumption has been predicted using artificial neural network models. Finally, the response of DPNs to critical conditions has been calculated and analyzed. The results indicate that in the critical conditions the natural gas pressure at the network nodes decreases. As a result, the natural gas velocity in the pipeline network increases and goes higher than the standard. The increasing natural gas velocity will cause erosion in pipelines and reduce safety in the natural gas supply process to consumers. In addition, the sudden pressure drop in some cases disrupts the process in natural gas regulators and causes gas breakdown. Using the results of this research, solutions for distribution pipeline networks in critical situations are provided for gas companies to use these solutions for gas supply.