Patent ID: 7030381

Claim:
A method for detecting a test gas that may be present at a measuring location, using an infrared gas analyser said analyser comprising: a cuvette accepting the gases to be analysed; an infrared light source located at one face side of the cuvette; an infrared detector located at an opposite side of the cuvette, the signals from the infrared detector serving the purpose of determining test gas recorded at the measuring location; and two gas lines serving the purpose of supplying gases to the infrared gas analyser wherein a first of said gas lines is adapted to take up a measuring gas at said measuring location that may contain test gas and where a second gas line is adapted to take up gas from the surroundings of the measuring location (reference gas), which gas may contain a test gas background that is to be taken into consideration when detecting the test gas taken up at the measuring location, wherein only one cuvette is present, said method including the steps of: taking up the measuring gas at the measuring location; feeding the reference gas to the cuvette of the infrared gas analyser such that the reference gas and measuring gas are alternately present, and where only in the instance that at the measuring location test gas is taken up the concentration of which in the measuring gas is higher than the test gas concentration in the reference gas, do the alternating signals that are supplied by the infrared detector serve the purpose of determining the increased test gas concentration.