The invention relates to an apparatus for spectroscopically analysing a gas,said apparatus having at least one radiation source (1), at least one detectionapparatus (12 20), at least one sample chamber (13) and a system of optical elements(4 5 6 7 9 10 11 18 19) which is intended and set up to direct at least part(3b) of the radiation (3) emitted by the radiation source (1) through the samplechamber (13) onto the detection apparatus (20), wherein the sample chamber (13)is used to hold a gaseous sample which contains the gas to be analysed, and whereinthe apparatus is configured in such a manner that the sample can continuouslyflow through the sample chamber (13), and means (16) are provided for the purposeof determining the pressure and/or the volume and/or the concentration of thesample in the sample chamber (13). The invention also relates to a correspondingmethod for spectroscopically analysing a gas.
