A method for detecting a test gas present at a measuring location, using an infrared gas analyzer having a cuvette, an infrared light source, an infrared detector, and two gas lines. A first gas line is adapted to take up a measuring gas at a measuring location that may contain a test gas to the cuvette. The second gas line is adapted to take up gas from the surroundings of the measuring location (i.e., reference gas), that may contain a test gas background that is to be taken into consideration when detecting the test gas taken up at the measuring location. To improve the sensitivity of the analyzer, only one cuvette and the measuring gas is taken up at the measuring location and the reference gas is fed to the cuvette such that each gas is alternately present therein.