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Introduction. The accuracy of the visibility analysis in the event of an indoor fire strongly depends on the smoke-generating ability of substances and materials obtained experimentally in small-scale units. Therefore, the task is to develop a method of analysis that takes account of the scale factor and does not use the specific coefficient of smoke generation to identify the range of visibility in a full-scale room.Goals and objectives. The goal of the research project is a new approach to the calculation of the time to the blocking of the escape routes due to the loss of visibility with due regard for the scale factor and without regard for the specific coefficient of smoke generation. To achieve this goal, the analysis of fire development patterns in small-scale and full-scale rooms was carried out; theoretical dependences between the volumetric average optical smoke density and other volumetric average parameters of the indoor gas environment were obtained for these patterns, and calculation results, based on the obtained dependences, were compared with the experimental data.Methods. Methods, employed by the co-authors, included solving non-stationary equations based on the principle of conservation of indoor gas energy, optical density of smoke and oxygen mass for the cases of closed and open-type indoor heat and mass transfer. Fire tests were conducted in a small-scale facility. Theoretical and experimental data were compared.Results. Analytical dependences between the volumetric average optical density of smoke, a change in the volumetric average temperature, and the volumetric average partial oxygen density for closed and open indoor fire patterns were obtained. The series of fire tests involving the PVC insulated and sheathed bare (coverless) cable, exposed to the effect of the varying density incident heat flux, were carried out. Experimental dependences between the time, the optical density of smoke, and the specific coefficient of smoke generation were obtained. The obtained volumetric average optical density of smoke was compared with the experimental data using the proposed analytical expressions.Conclusions. The co-authors suggest using experimental dependences between the volumetric average optical density of smoke, changes in the volumetric average temperature or the volumetric average partial oxygen density obtained in a small-scale facility without solving the differential equation based on the principle of conservation of optical density of smoke.

A comparative analysis of methods of carrying out fire tests was carried out in order to obtain the value of smoke formation coefficient required for simulation of fire dynamics at power engineering facilities. A new method of carrying out fire tests to determine smoke-forming ability of substances and materials is proposed. Results of measurements of radiant heat flux density and gas medium temperature inside combustion chamber at different distances from heating element are presented. The effect of the sample area, the density of the heat flow incident on the sample and the temperature inside the combustion chamber on the value of the smoke formation coefficient is shown. For modern types of cable products used at power engineering facilities, values of smoke formation coefficient under different modes have been determined. Dependence of smoke formation coefficient on sample area and on distance from heating element inside combustion chamber is obtained. A comparative analysis of the results obtained at different facilities with the values given in the database of typical fire load was carried out. It was found that the experimental value of smoke formation coefficient differs significantly from the values obtained in the standard ГOCT12.1.044 facility. The results were analyzed.

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