This work investigates the compression of gases in a closed volume with presence of condensation centers in it. An equation describing the output molecules from the gas phase when it is compressed was suggested. The solution to this equation predicted the existence of two regimes in the development of this process and the possibility of transition from one to the other at a point. We analyzed the effect of the number of condensation centers on the view of the proposed equation, and, consequently, on the process of removal of molecules from the gas phase. Using the obtained results it was proposed the equation of state of real gases, which physically correctly describes their compression and condensation on the active centers. Applied approach to the analysis of the studied system allowed... a logically consistent way to obtain the isotherm of polymolecular adsorption, containing the main elements of the experimental curves and a different more simple form from known equations.