An embodiment of the invention provides a method for monitoring for and detecting a leak in a line where a mobile detector having an audio sensor and an odor sensor transiting along the line. A sample audio reading is obtained by the audio sensor; and, a sample odor reading is obtained by the odor sensor. A processor compares the sample audio reading to a baseline audio reading to determine whether the line is leaking. The processor compares the sample odor reading to a baseline odor reading to determine whether the line is leaking. The location of the mobile detector is identified by a GPS device on the mobile detector when the processor determines that the line is leaking. The location of the mobile detector, the sample audio reading, and the sample odor reading is sent to a central monitoring center by a communications device on the mobile detector.