Beams (11) and (13) produced by helium-neon gas lasers (10) and (12) are directed at photoacoustic absorption cells (20) and (21) containing a flowing sample gas stream recovered from coal, oil and natural gas well drilling. The common hydrocarbon gases and vapors within cell (20) highly absorb the infrared energy emitted by laser (10) thereby producing an acoustic disturbance which is detected by a transducer (34) which produces an electrical output signal proportional to the concentration of the hydrocarbon gases and vapors. The methane gas within cell (21) weakly absorbs the infrared energy of laser beam (13), and thus the resulting output signal produced by a transducer (35) serves as a reference signal for determining the methane concentration. The output signals from transducers (34) and (35) are used by data processing unit (40) to compute the total concentration of hydrocarbon gases and vapors and the concentration of methane gas within cells (20) and (21). A turnable carbon dioxide gas laser (44) produces laser beams (45) and (47) both in the infrared region which are highly absorbed by the propane and n-butane component gases, respectively, flowing through photoacoustic cell (48). The level of energy absorbed from these two beams, as determined by the energy of the acoustic disturbance produced within cell (48) induces production of an electrical output signal by transducer (56) at levels proportional to the concentrations of the propane and n-butane gases in cell (48). The output signals from transducer (56) are then used by data processing unit (40) to compute the concentrations of propane, n-butane gases and C.sub.5.sup.+ gases in the sample.