A device which: optically detects the presence of, measures the flow rate of, and identifies the characteristics of venting fugitive gas emissions. Specifically the device provides a spectral analysis of emission gas constituents; selective detection of the presence of venting hydrocarbons; measurement of venting emissions flow rates, the measurement of shut-in and flowing venting system pressures and the venting system temperatures. The flow rates are corrected, relative to the detection of the gas constituents and standard temperature and pressure (STP). These devices are configured to collect such data electronically and transmit via various telemetry systems, to a secure remote data network for reporting, access, evaluation, real-time monitoring and archiving as required.