The comparative evaluation of the criteria used to determine the critical values of the partial density of carbon monoxide as part of the calculation of time to the blocking of escape routes in case of a room fire

Introduction. Critical values of the partial density of gas, the toxic dose or relative mass of carboxyhemoglobin in human blood serve as the criteria determining the time to the blocking of escape routes due to the presence of carbon monoxide. However, the comparative analysis of the effect produced by the selected criterion on the time to the blocking of escape routes due to the presence of this gas has not been conducted yet. Goals and objectives. The purpose of the article is to compare the values of the time to the blocking of escape routes by carbon monoxide obtained using various methods of determining the critical values of the carbon monoxide density. Towards this end, experimental studies on combustion processes of various solid and liquid combustible substances and materials were conducted in a small-scale test unit, and calculations of the time to the blocking of escape routes with carbon monoxide were made on their basis. Theoretical fundamentals. The amount of carbon monoxide, inhaled during a fire, is calculated using experimentally measured partial densities of CO and mathematical models designated for the calculation of the toxic dose of this gas and formation of carboxyhemoglobin in human blood. Results and discussion. Experimental dependencies between the testing time and medium-volume densities of monoxide emitted during the combustion of the “low smoke” PVC cable sheathing, timber (pinewood), chocolate, transformer oil and vegetable oil are presented. The authors obtained theoretical dependencies between the toxic dose and mass concentration of carboxyhemoglobin in human blood, on the one hand, and the time for the combustible materials, analyzed in the article. It has been found that the values of time to the blocking of escape routes due to the presence of carbon monoxide may differ significantly depending on the method used to determine the critical values of the carbon monoxide density. Conclusions. Standard methods, used to calculate the time to the blocking of escape routes due to the presence of carbon monoxide, employ the value of the critical partial density which may involve a substantial overestimation of the above time frame and the underestimation of the toxic effect produced on a person in the process of his/her evacuation. Therefore, it is necessary to apply all methods, discussed in the article, to select the minimum value of the above time frame.