These investigations were conducted in a standard barn for 200 stanchion cows in the summer period with a special electronic device, the analysis of the obtained data was made with the use of graphical information modelling, the results demonstrated, that CO2 concentration was from 700 till 1200 ppm average and did not exceed 50% of the maximum permissible concentration. The lowest CO2 concentration was registered on the windward and leeward side of the barn; and the highest one was registered about in 1.4-1.9 times higher in the central part of the barn.