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Hydrocarbon leaks in oil and gas installations present Health, Safety and Environmental risks. History of crisis management in oil and gas upstream has shown the value of efficient and accurate tools for quantifying the gas-leak rate and determining the perimeter of the hazardous areas. In this context, Total initiated a multi-year R&D collaborative project designed to develop remote sensing technologies and architectures for remote detection, identification, quantification and visualization of gas leaks in the event of a crisis. Total, the ONERA – The French Aerospace Lab – and ADCIS have developed a set of algorithms and software to measure, compute and visualize a methane plume using infrared optical imagers. Results are obtained in 3D and in real time. The following steps are involved: (1) Spectral images in the Long-Wavelength InfraRed (LWIR) region are captured by three hyper-spectral cameras located around a methane release point; (2) Concentrations of methane are measured linearly in ppm.m by comparing spectral images of the scene in the presence of gas and reference images acquired before the release; (3) An algorithm, drawing on tomography techniques, computes concentrations of methane in ppm from the linear concentrations; (4) Mass balance type equations finally help estimate the methane flowrates based on the set of concentrations and local wind data information. A one-week test campaign was organized in September 2015 and consisted of performing twenty-six methane gas releases of 1 g/s to 50 g/s. Three Telops Hyper-Cam cameras were connected as part of a network to a main server which ran the tomography and flowrate estimation code. The real-time remote detection and quantification worked fully. During the campaign, good accuracy was obtained at the low flowrates of 1 g/s and 10 g/s of methane. At the higher flowrate of 50 g/s, quantifications were underestimated due to an oversaturation phenomenon. Further works, the aim of which is to adapt the instrument sensing ranges to the maximum concentrations encountered, should help improve the accuracy of these quantifications. The innovation lies in the fact that a 3D visualization of the methane plume can be computed and created in real time and that flowrates and concentrations can be quantified, also in real time. This technology could be applied in environmental monitoring and crisis management.