The aim of the research was measure changes asbestos dust concentration over long period of use in old building systems. Buildings from different systems during their exploitation and after asbestos removal were tested. Asbestos dust concentration decreasing in some building systems is due to air exchange and other phenomena, if there are no new active dust sources. Currently, with proper use of those buildings, average values of dust concentrations did not exceed range 300 - 400 f / m3 with a downward trend to <300 f / m3. The results of these studies were obtained with a modified optical microscopy technique and verified by SEM and TEM methods. The graphical trend of the variability contaminations allows estimate them in the future better then theoretical models. Research proves that a single measurements done in short time as an applicable obligatory immediately after the asbestos removal may not detect the hazard appearing after some time. Monitoring buildings over longer periods of time allows to detect significant changes in their contamination. In many cases the minimal air contamination undermines the desirability of removing asbestos in old buildings