Introduction. Presently, there are no model loads that describe the burst effect of an internal explosion. The goal of the article is to design a model load that characterizes an internal explosion with regard for the effect of inertial safety structures. The author provides relevant examples.
Methods. The experiment and the numerical modeling identify the characteristics of an internal explosion, primarily, its destructive effect. First of all, these characteristics include the pressure value and rate in the process of the first peak formation. A drop follows the first peak. Another rise to the second peak is followed by the final pressure drop. The rise to the first peak is described by a cubic parabola. The constant value of pressure is equal to the highest value of the two peaks. It replaces the drop and rise between the peaks. The linear dependence describes the area of the final pressure drop, so that the deformation is completed at the end point. The time of the pressure rise is determined by breakup, and it takes account of the characteristics of safety structures. The time of the second peak is the time when the flame area is maximal.
Results and discussion. The deformation that may occur before the first peak represents a solution to the equation, describing the beam motion. This equation is provided in the article. The deformation between the peaks is determined by the balance of energy. The deformation, that occurs when the pressure drops, is identified by the solution to the motion equation. The solution is subject to the deformation completion condition.
Conclusions. The results show that the time between the peaks is important when the pressure is close to maximal. The analysis identifies the conditions under which deformation remains elastic. These results can be contributed to the assessment of the bearing capacity of buildings that accommodate explosive production facilities. This approach ensures conservative results.

Introduction. The international practice of passive fire protection design, as well as some manufactures of fireproofing products recommend to apply fire proofing substances not only to the main element, whose fire resistance limit is standardized, but also to the elements that do not fall under any fire resistance standards. Various support brackets, pipeline supports (hereinafter — PS), etc. can serve as examples. They are not considered as bearing elements according to SP (Construction Regulations) 2.13130.2020, although they are connected to the structures that have fireproofing applied. It is recommended to apply fireproofing substances to such PS within the range of, at least, 450 mm from the point of attachment to the fireproof structure when the area of the PS cross section exceeds 3,000 mm². No “supplementary” fireproofing is required by the Russian design and fire protection regulations.
The subject of research. A change in the fire resistance limit of steel i-girders, caused by the PS heating, depends on the area of the PS cross section and the location of the point of its attachment.
The goal. The goal of the research is to analyze the effect, produced by the area of the cross section and the point of attachment, on the fire resistance limit of fireproof steel i-girders in the course of heating.
Materials and methods. ANSYS Workbench 2020 R2 (student version) was applied to perform the numerical simulation.
Results. The simulation has shown that the PS, having no fireproofing, influences the fire resistance limit of fireproof structures.
Conclusions. Currently available methods of analysis of the fire resistance of steel structures take no account of the fire resistance limit reduction, caused by the heating of the PS that has no fireproofing. The numerical simulation has shown that the fire proofing design must take account of the potential reduction in the fire resistance limit of fireproof structures, exposed to the heated PS that has no fire proofing. The further verification of the effect, produced by the PS, that has no fireproofing, on the time to the limit state of a fireproof steel i-girder requires fire tests and supplementary investigations to evaluate the influence of the PS on the heating of vertical fireproof constructions, including the case of the hydrocarbon fire mode.

Introduction. One of the main objectives, pursued by the information analysis support extended to smoke divers, is the preparation of indoor routes. Technical capabilities, represented by advanced remote monitoring systems, provide a fire extinguishing manager with the necessary information about the point of fire origin and mathematical tools allow to predict fire spreading characteristics. The goal of this work is to develop an algorithm for the preparation of an optimal indoor route for smoke divers to support management decisions in the event of fire. To achieve this goal, it is necessary to develop the theoretical framework and implement it in a software programme.
Theoretical foundations. The theory of cellular automata is employed in this paper to simulate the routes of smoke divers inside a building. A cellular automaton with a Moore neighborhood is applied. We use differential equations, similar to the Kolmogorov equations, to monitor the fire parameters.
Results and discussions. A modified wave algorithm was developed to determine the optimal indoor route. The software tool was applied to simulate the route of gas divers. Coefficients of importance were applied in the process of mathematical modeling; they took account of the prioritized work to be performed by smoke divers.
Conclusions. The results of the study suggest that the algorithm allows to identify the optimal itinerary, thereby enabling the decision maker, responsible for sending teams of smoke divers to the work performance location, to make a reasonable choice of the point of entry for the personnel and machinery, as well as their itinerary inside the building.

Introduction. The relevance of the topic, addressed in the article, is backed by the fact that modern heating systems, such as the underfloor heating, remain potential sources of fire, despite the improvement in their designs. The purpose of the study is to identify the causes of fires that occur in the process of operation of modern heating systems “Underfloor Heating”; to analyze and generalize the conclusions made by the fire safety experts in respect of the heating systems analyzed in the article.
Materials and methods. To assess the flammability of the infrared film underfloor heating, an experiment was conducted by the experts: the process of underfloor heating was simulated under normal environmental conditions at room temperature.
Results and discussion. The experiment has shown that the floor covering, made of the material capable of accumulating heat, is the most dangerous one, although its small area prevents its disconnection from the thermal sensor. When dismantling the construction, the co-authors found out that the foil insulator had been melting in the area of maximal temperatures. Over the course of seven hours of operation, the temperature exceeded 120 ºC, and after that the odor of products of thermal decomposition of a synthetic product appeared.
Conclusions. Despite all the features of advanced underfloor heating systems, their automated operation and transformation, they remain potentially flammable. Modern underfloor heating systems can take fire both as a result of violation of the fire precautions in case of non-compliance with the requirements for the operation of heating devices, and as a result of overheated film heaters located under the floor covering.

Introduction. Fires in high-rise buildings and structures constitute a grave danger both to the people inside, valuables, and the building structure. More often than not, fires develop on the external surface of construction facilities that are in operation or inside those facilities that are under construction, and they give rise to the problem of using standard fire extinguishing solutions and require the employment of mobile machinery by fast response units of the fire-fighting service who apply fire extinguishing agents from the outside of a building. The purpose of this article is to substantiate the in expediency of, or, on the contrary, the need to make the proposed amendments to Federal Law No. 123-FZ of July 22, 2008 “Technical Regulation of Fire Safety Requirements”.
The scope of the problem. The analysis of the effectiveness of various methods of application of fire extinguishing agents used to extinguish outdoor fires in high-rise buildings has shown the insufficiently high efficiency of ground-mounted machinery, which preconditions the need to make an enquiry into the possibility of using aircraft to extinguish high-rise buildings and structures. Given the need to ensure effective fire extinguishing, meet safety and economic feasibility requirements, an autonomous unmanned aerial vehicle (AURA) was selected as the delivery vehicle. Systems using various fire extinguishing agents and methods of their application were used for fire extinguishing purposes, including a pulsed water application system, capsules containing the fire extinguishing composition, high-pressure water mist and compressed air foam. Their applicability at the height of 300 meters has determined their choice.
Research results. The testing task was to confirm the possibility of application of fire extinguishing agents to the fire seat in the course of the flight of an unmanned aerial vehicle, to identify the effectiveness of fire extinguishing agents and to assess the stability of extinguishing agents applied to the fire seat. To ensure safety, testing was carried out at the height not exceeding 10 m, and the results confirmed the possibility of using the above substances to extinguish fires.
Conclusions. The research has confirmed the possibility of using unmanned aerial vehicles and various methods of fire extinguishing by means of the horizontal application of extinguishing agents inside high-rise buildings and structures, if extinguishing agents are applied from outside of a construction facility.

Introduction. Two-storey church buildings, that date back to the past centuries, are usually regarded as monuments of history and architecture. Their facades cannot be changed when buildings are adapted for modern use. The ground floor of a church building is used as a warm winter church, and the first floor is an unheated summer church. The evacuation of church members from the ground floor in case of fire is organized in accordance with fire safety regulations. If the area of the upper church floor is 80…200 m2 or more, the number of people may exceed 100 people there. As a rule, the upper church has one evacuation exit, which is contrary to the fire safety regulations, that prescribe the availability of several exits from the upper church floor when the number of people there exceeds fifty. The purpose of the article is to propose fire safety amendments in respect of cultural heritage monuments, so that the acceptable number of people inside a church building, that has one exit, can exceed fifty.
Theoretical foundations of amendments to fire safety regulations. Methods of flexible fire safety control, applied today, allow for the regulatory harmonization of the requirements applicable to the adaptation of immovable cultural heritage for modern use. The level of individual risk is the fire safety criterion for a two-storey church building.
Substantiation of effectiveness of the fire safety system. A system of measures is proposed to ensure the fire safety of two-storey church buildings. The proposals will allow to increase the number of people on the first floor, so that it can exceed fifty. The case of a functional church is analyzed, which demonstrates methods of increasing the number of people inside it to one hundred. The results of modeling the process of evacuation from the upper church floor are presented.
Conclusions. An individual risk, arising in a church building that has one exit, is analyzed, and the implementation of the fire safety criterion is substantiated. Draft amendments to the fire safety regulations have been proposed, so that the number of people inside a church building, that has one exit, can exceed fifty.

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.

Introduction. The problem of timely activation of fire sprinkler systems is highly relevant for effective fire suppression before the critical moment, when calculated values applied to extinguish the fire, become ineffective. A number of works address the problem of effective application of the fire sprinkler system to Class A fires. The application of such methods to Class B fires has not yet been considered.
The model simulating a fire in a room with an automatic fire extinguishing system. The response time assessment model, developed by the co-authors for an automatic water-consuming fire sprinkler system, allows to identify the velocity of flame spreading over the surface of an HFL/CL spillage and the temperature rise rate in the ceiling area in the case of a B class fire.
A sprinkler is triggered by the bulb bursting caused by the thermal effect produced by the ascending convection flow. A model has been developed to determine the response time of a fire sprinkler system exposed to the effect of a heat flow, caused by the Class B fire, on a heat-sensitive sprinkler bulb.
Activation of a fire sprinkler system by the rate-of-rise heat detector. A model, designated for determining the activation time of a rate-of-rise heat detector, was developed.
Examples. A number of examples, illustrating the response time of traditional, deluge, and forced launch fire sprinkler systems, are provided in the article.
Conclusions. The obtained formula allows to quickly check the applicability of different types of fire sprinkler systems to ensure the effective protection of premises in which class B fires may break out.