Engineering Physics Annotation << Back Differential Absorption Lidar for Continuous Gas Monitoring in a Tunnel Near the Elbrus Volcano Ponurovskiy Ya.Ya., Pershin S.M., Grishin M.Ya., Zavozin V.A., Lednev V.N., Makarov V.S., Stavrovsky D.B., Ushakov A.A. A differential absorption LIDAR has been developed based on tunable diode lasers for continuous monitoring of gases in a tunnel near the Elbrus volcano. A long-term monitoring has been carried out for the fi rst time for different gases (carbon dioxide, water vapor, hydrogen sulfi de) including the selective detection of 12CO2 и 13CO2 . It has been demonstrated that atmospheric pressure variations impact the gas emission dynamics, so it could hide the gas signals associated with the seismic activity. We demonstrate that atmospheric pressure variations do not affect the ratio of 13CO2 / 12CO2 concentrations, thus this ratio could be a promising indicator for early detection of seismic activity. Keywords: differential absorption lidar, seismic activity, gas emission, earthquake precursors. DOI: 10.25791/infi zik.1.2024.1377 Pp. 03-13.