A system and method of detecting gas leakage along an underground pipeline system accurately determines the presence of a gas leak while minimizing cost and preserving energy. The system includes at least one underground pipeline with a plurality of stack vents, a plurality of sensor units, and at least one remote server. Each sensor unit is mounted within a stack vent. The method begins by tracking a current time with each sensor unit. A gas-concentration reading with at least one specific unit is captured and then communicated along with a sensor location and a sensor identification to the remote server and recorded with the remote server. The tracking, capturing, and communicating of the gas-concentration reading is repeated so that actual gas-concentration data is compiled and compared to a baseline gas-concentration data or a defined gas-concentration threshold. A leak notification for a gas leak is then sent with the remote server.