A device can be used for establishing gas concentrations in an examination volume. A radiation source is configured to generate an electromagnetic beam. A beam guiding apparatus is arranged downstream of the radiation source. The beam guiding apparatus is configured to set a plurality of variations of beam guidance of the beam entering the beam guiding apparatus in an observation plane in the examination volume. A spectrometer is arranged downstream of the beam guiding apparatus. The spectrometer is configured to carry out a spectral analysis of the beam leaving the beam guiding apparatus. An evaluation unit is configured to establish in the observation plane a 2D concentration distribution for one or more gases in the examination volume on the basis of the spectral analysis for different variations of beam guidance.