Performance evaluation of quantitative optical gas imaging (QOGI) technique for fugitive methane emission quantification

Quantitative Optical Gas Imaging (QOGI) is increasingly adopted to support Leak Detection And Repair (LDAR) programs and process safety monitoring; however, its quantitative performance strongly depends on operating and environmental conditions. This study presents a controlled laboratory assessment of the performance of a QOGI system, with particular focus on methane emission rates close to the declared Minimum Leak Detection Rate (MDLR) of the instrument. Fourteen experimental configurations are investigated by systematically varying key parameters, including measurement distance, wind conditions, thermal contrast between the gas plume and the background, framing, and viewing angle.The results show that, under favorable operating conditions, QOGI provides a stable and highly consistent response, with good linearity between measured and actual emission rates. From a statistical perspective, the median is identified as the most robust central tendency index when a limited number of acquisitions is available, making it particularly suitable for practical field applications. Measurement distance is identified as the primary driver of performance, while correct wind configuration is essential to avoid systematic bias. Thermal contrast further enhances stability, whereas observation geometry has a marginal influence when the plume is fully captured.Overall, the study identifies an optimal operating window in which QOGI delivers reliable and decision-useful quantitative information, providing practical guidance for its effective deployment in process safety, LDAR applications, and regulatory contexts.