The calculation of non-gray radiation absorptivity and absorption coefficient of the mixture of gases at different temperatures and atmospheric pressure have been performed using spectroscopy database HITEMP-2010. First, the non-gray transmissivity results have been validated from the theoretical results published in open literature, then the variation of absorption coefficient for the mixture of CO 2− N 2, H 2 O− N 2 and air at different temperatures and atmospheric pressure have been presented. A comparison between the Voigt and Lorentz line profiles has also been shown. Both the line profile shapes are found to be in excellent agreement with each other. The high value of absorption coefficient of air has been noticed in the shorter wavenumber values that decreases with the increase of temperature. There is one order decrease in the value of absorption coefficient for air at 1000 K than when compared to air at 300 K. The air bahaves as transparent in the spectral range beyond 4000 cm-1.