The field measurement of transmission of 12C16O2 , 12C18O2 and
13C16O2 laser at 62 wavelenghts in the 9.2-11.2 ?m spectral range are presented. The measurements were made on a 0.2-2.0 km horizontal path using a tunable CO2 laser. The results were compared with the computed molecular absorptions. Rather a good agreement has been found. Under sufficient visibility (disregarding aerosol attenuation) atmospheric water vapour is the main extinction component within 10-13 ?m
and in the range of 8-10 ?m other small constituents are importent.