NOVELTY - Photoacoustic detection for measuring concentration of non-hydrocarbon component of methane-containing gas mixture, comprises setting measuring range so that it contain at least2 separate characteristic methane absorption wavelengths of different absorption strength, and characteristic absorption wavelength(s) of the non-hydrocarbon component.    USE - For photoacoustic detection to measure concentration of non-hydrocarbon component of methane-containing gas mixture (claimed).    ADVANTAGE - The invention provides high-precision and extremely sensitive detection. It can be easily automated and carried out continuously without abruption. It gives accurate and reliable results even for significant methane contents, and can be successfully used even when the gas mixture contains inevitable alcoholic vapor residual coming from antecedent penetration processes.    DETAILED DESCRIPTION - Photoacoustic detection for measuring concentration of non-hydrocarbon component of methane-containing gas mixture, comprises leading gas mixture through acoustically optimalized photoacoustic measuring cell (2) while it is illuminated through periodically modulated light source (1); detecting periodic changes in pressure due to the illumination and converting into photoacoustic signals using pressure change sensor built into the photoacoustic measuring cell; recording photoacoustic absorption spectrum of the gas mixture by varying the wavelength of the illuminating light source; setting measuring range so that it contain at least2 separate characteristic methane absorption wavelengths of different absorption strength, and characteristic absorption wavelength(s) of the non-hydrocarbon component; settling exact position(s) of the concerned absorption wavelength(s) of the non-hydrocarbon component in measuring range on basis of reference photoacoustic absorption spectrum recorded in reference cell (3) arranged behind the measuring cell and illuminated by light source; establishing photoacoustic signal's dependence on the concentration of the non-hydrocarbon component; defining a quantity Xm depending purely on methane-concentration for the chosen characteristic methane absorption wavelengths on basis of photoacoustic absorption spectrum recorded for the gas mixture, and determining photoacoustic signal strength (Ym) at one of the characteristic methane absorption wavelengths concerned; subjecting the spectrum recorded for the gas mixture to a transformation achieved by combination of the quantities Xc and Xm and the photoacoustic signal strengths Yc and Ym; and determining the sought concentration of the non-hydrocarbon component of the gas mixture using the spectrum transformed as a start, and exploiting the relation between the concentration of the non-hydrocarbon component and photoacoustic signal.    DESCRIPTION OF DRAWING(S) - The figure is a diagrammatic representation of the measuring apparatus for measuring concentration of non-hydrocarbon component of methane-containing gas mixture.    Light source (1)    Photoacoustic measuring cell (2)    Reference cell (3)    Electronic unit (4)    Personal computer (5)    Light beam (6)    Gas inlet (7)    Gas outlet (8)    Microphones (9)