Research aim is to study basic regularities in functional condition change of main fans included in the confi guration of main mine ventilation installations depending on the technological service conditions. The research also aims to determine the standard service life of main fans with the account of the diff erential analysis of the destructive factors, structural features, intensity and modes of operation of ventilation plants. 108 "Izvestiya vysshikh uchebnykh zavedenii. Gornyi zhurnal". No. 6. 2020 ISSN 0536-1028 Research methodology. Based on the analysis of main fan installations structure and differential analysis of technological factors affecting the functional efficiency of main fans, a mathematical model has been proposed which determines the standard and residual life of the main fan with the account of the changing load. Results and analysis. As a result of studying the impact of destructive factors on the main functional parts of the main fan, an equation has been proposed, which takes into account the physical properties of the material the fan elements are made of together with the quantitative effect of the external physical factors on the machine’s operation. Research results show that the resource of the main fans should be determined based on the useful life of the machine’s major component, i.e. mainshaft, with the account of the machine’s operation mode. Conclusions and scope of results. Circuit designs of mine ventilation plants predetermine the main fans service life. The service life should be established at the stage of the detail design with the account of the differential analysis of the destructive factors, structural features, intensity and operation modes of ventilation plants. The proposed methodology for main mine fans residual life determination is applied in expert organizations and Guidances on the determination of residual life of main mine fans which operate under the excess of the standard service life. The methodology may also be applied by project organizations to determine the design service life for the constructed main ventilation installations.