Calculated spectra of the Fermi triad of CO2 absorption bands were studied ranging from room temperature to 1500K. Based on the Voigt calculations, the R(32) transition of the nu1 + 2nu2 + nu3 band is proposed for combustion CO2 monitoring. The transition was experimentally recorded at various conditions and compared to Voigt profiles. It is proved to be a suitable transition for combustion CO2 detection.This work examines the application of Tunable Diode Laser Absorption Spectroscopy (TDLAS) to monitor high temperature CO 2 and O2. The selection of the optimum absorption line is the focus.Similarly, O2 spectra near 760nm were studied. The Voigt calculation shows that the transitions near the violet end of the b1 g+ (v'' = 0) ← X3 g- (v" = 0) band are potential for high temperature oxygen measuring. The follow-up experiments indicate that the RQ 25 transition offers a good balance of sensitivity and suppressed room temperature oxygen interference and is suggested for high temperature oxygen measurements.