A high-resolution external laser photoacoustic spectrometer has been developed for trace gas detection with absorption transitions in coincidence with CO 2 laser emission lines (9,2-10,9 μm: 920-1086 cm - 1 ). The CO 2 laser operates in 90 CW lines with power of up to 15 W. A PC-controlled step motor can tune the laser lines. The resonance frequency of first longitudinal mode of the photoacoustic cell is at 1600 Hz. The cell (3-factor and cell constant are measured close to 50 and 28 mVcmW - 1 , respectively. The spectrometer has been tested in preliminary studies to analyze the absorption transitions of ozone (O 3 ). The ethylene (C 2 H 4 ) from papaya fruit is also investigated using N 2 as carrier gas at a constant flow rate.