We studied experimental spectra of CO2 and CH4. The proposed model provides a reasonable bandshape for the case of CO2. For the case of CH4, the agreement of experimental and calculated spectra is observed for the central region of the band; in the peripheral region significant discrepancies have been observed. They are related to the influence of the adiabatic effects on the line interference. The atmospheric irradiation is calculated for the spectral region 719 - 722 cm-1 situated in the higher frequency wing of the CO2 band corresponding to the 10001-01101 transition whose shape is essentially influenced by line interference. The calculations are performed for tangent heights 6 - 35 km which were expected to reveal the greatest effect on the outgoing radiation. The calculated effect varies essentially with tangent height providing the lack of radiance of more than 10 mW / (m2. sr cm-1) for tangent heights 17 and 20 km when the line mixing effect is taken into account. The preliminary analysis of the available ATMOS experiment data set has been done. For correct comparisons with calculations, the registered transmission data should be normalized. For accurate determination of the calibration parameters it is valuable to obtain additional data on absorption band wings of major atmospheric constituents.