Currently, a very big problem of cities in Europe and the world is air pollution with combustion products of car fuels, generation of heat and electricity. These impurities affect the microclimate of cities significantly. Pollution not only affects the area outside buildings, but getting into their interior through ventilation systems, which has an adverse effect on the indoor environment of buildings. High concentrations of CO2, cause a weakening of concentration in working people, which affects the deterioration of safety and work efficiency. For assessing air quality improvement on “green roofs”, a field study of CO2 content has been carried out on the “green roof” of a four-storey building, on a completely identical non-greened building, and on a highway with high-density traffic near them in Kiev. It was found that greening the roof significantly reduces the CO2 content from 501 ppm on the road and 452 ppm on the roof without protection to 410-415 ppm. It improves the conditions in which people work and rest.