Gas distribution network is a system of external pipelines from a source to a gas consumer service line as well as facilities and engineering devices for them. An external pipeline is an underground, aboveground and/or overhead pipeline laid outside of the buildings to an outer building structure. Natural gas flows into the high pressure gas distribution network from the gas trunkline through a gas distribution station, and into the medium and low pressure gas distribution network – through gas distribution points.

There are the following gas pipelines of gas distribution systems classified according to their function:

• gas trunklines (town and inter-settlement) laid to the main gas distribution point;
• distribution pipelines (street-level, intra-block, interplant and others) laid from gas distribution points to customer service lines;
• service lines laid from the connection with the distribution pipeline to the shutdown device at the building infeed;
• entrance gas pipeline – from the shutdown device;
• internal gas pipelines laid from the gas pipeline infeed to the connection with the gas appliances.

There are low (up to 0.05 MPa), medium (0.05 to 0.3 MPa) and high (0.3 to 0.6 and 0.6 to 1.2 MPa) pressure gas distribution network pipelines. Source type and configuration of a gas distribution network are determined by gas consumption volumes, structure and housing density, etc.