Introduction. There are estimates of the maximum size d_cr of explosive particles of the two types of sulfide ores. The estimates are based on a qualitative approach to the dispersion analysis of combustible ore specimens (Soundararajan, Amyotte & Pegg, 1996): 49 μm < d_cr, PO < 63 μm for pyrrhotite (PO) and 85 μm < d_cr, PY < 145 μm for pyrite (PY). The task was to refine these estimates using the quantitative method of the mentioned analysis, taking into account the lower explosive limit (LEL) of flame propagation in terms of ore suspensions. Experimental data processing method. Continuous functions F of particle size distribution d were constructed for the two polydisperse specimens of pyrrhotite (LEL_PO,1 = 475 g/m³ and LEL_PO,2 = 1,375 g/m³) and two polydisperse specimens of pyrite (LEL_PY,1 = 375 g/m³ and LEL_PY,2 = 500 g/m³). The obtained functions F_PO,1(d), F_PO,2(d), F_PY,1(d) and F_PY,2(d) were converted using Rosin – Rammler distributions, filling the gaps between the discrete data of the grain-size analysis of the specimens. d_cr rating. The procedure for estimating d_cr (Poletaev, 2014) was employed to find the values of d_cr, PO and d_cr, PY using the following equations: F_PO,1(d_cr, PO)/F_PO,2(d_cr, PO) = LEL_PO,2/LEL_PO,1 and F_PY,1(d_cr, PY)/F_PY,2(d_cr, PY) = LEL_PY,2/LEL_PY,1. The solutions were presented in the visual graphic format.

Discussion of the results. Due to the low values of explosion parameters of pyrrhotite and pyrite in a 20‑liter chamber (maximum explosion pressure P_max ≤ 350 k_Pa, index K_st ≤ 2 M_Pa ∙ m/s), the validity of classifying ores as explosive dusts was discussed. Low explosion values have proven that sulfur is the main fuel in the air suspension. The explosiveness of ores is proven empirically (Selle & Zehr, 1954) by estimating the combustion temperature, which exceeds 1,000 °С.

Conclusions. The values of d_cr for sulfide ores have been refined: for pyrrhotite, d_cr = 40 μm; for pyrite d_cr = 107 μm. In the air suspensions of ores, only sulfur is burnt out, which substantially reduces the explosiveness of ores.

Introduction. The article considers an accidental indoor gas explosion on condition of pressure relief through openings in which venting structures were installed.

A solution to this problem can protect residential buildings from consequences of explosions due to the fact that the volume of premises in residential buildings is small compared to industrial buildings, and it determines more stringent pressure relief conditions at the initial moment of the explosion development. The article shows that pressure can reach critical values in a small space during the motion of a venting structure in the opening before the onset of pressure relief.

Goals. The authors aim to identify the pattern of blast load development from the moment of explosion to the attainment of the maximum pressure value with account taken of the properties of venting structures and patterns of their opening. This goal is relevant due to the fact that until now at this stage pressure development has been considered without any account taken of how deeply the venting structure is installed in the wall opening. Much attention was focused on the selection of the opening size.

Methods. The methods of the theory of dimensions, numerical and analytical modeling of explosion processes, patterns of gas escape and rigid body motion were applied to obtain dimensionless groups describing the development of an explosive load until maximum values. These dimensionless groups allow identifying explosive loads for rooms having different volumes, which is also a new result.

Results. In this work, the influence of individual factors on the ultimate result has been identified. These factors are the room volume, the pressure at which the venting structure starts moving, the mass and position of the venting structure in the opening, the opening perimeter and the rate of explosive combustion.

Conclusions. The results, obtained in the course of this work, allow identifying the dynamic load of an explosion at the stage of its growth. This value can be used to set more reliable bearing characteristics of structures for cases of accidental explosions in living accommodations.

Introduction. One of the ways to reduce the fire hazard at industrial facilities is the application of intumescent coatings. It is known that intumescent compositions are multicomponent composite materials, whose effectiveness is due to complex chemical transformations of the components of the studied flame retardant exposed to high temperatures. In this regard, the problem of studying the physicochemical processes and thermophysical characteristics of flame retardant thermal expansion materials is in demand and relevant.

The purpose of this article is to analyze the thermophysical properties of water- and acrylic compound-based intumescent flame retardants to improve the safety of oil and gas facilities.

To accomplish this purpose, the following objectives were attained:

• studying acrylic dispersion-based intumescent flame retardant materials using methods of thermal analysis;
• analyzing aqueous dispersion-based intumescent flame retardant materials using methods of thermal analysis;
• making a comparative analysis of the thermo-oxidative degradation of the studied flame retardant materials.

Methods. During the study, thermogravimetric analysis, differential thermogravimetric analysis, differential scanning calorimetry, and quadrupole mass spectrometry were chosen as the main methods.

Results. As a result of the studies performed using methods of synchronous thermal analysis of water- and acrylic compound-based intumescent flame retardants, the similarity of ongoing physicochemical processes was identified, including the presence of four main stages of mass loss and a high exothermic effect. This high thermal effect has proven high flammability of the studied flame retardant materials.

Conclusions. Following the analysis, the authors have concluded that intumescent flame retardants, containing acrylic vinyl acetate emulsion and aqueous dispersion, begin to lose their performance characteristics, necessary for a flame retardant material, when the temperature reaches approximately ~600 °C.

Introduction. Large amounts of pollutants, including carbonaceous particles of soot, are released into the atmosphere during a forest fire. High concentrations of these particles in the air can lead to the development of cardiorespiratory diseases or death. It has been noticed that a certain number of soot particles is produced at the stage of forest fuel pyrolysis. In this regard, it is advisable to study the processes of pyrolysis and sooting to develop effective methods of their prediction and prevention.

Goal of the study. The goal of this study is the mathematical simulation of heat transfer in an element of standard forest fuel (a birch leaf), taking into account the thermal decomposition of dry organic matter and sooting.

Materials and methods. Within the framework of the work, scenario modeling of heat and mass transfer processes in an element of forest fuel (a birch leaf), subjected to the influence of a high-temperature environment, was conducted. A one-dimensional heat transfer equation and a kinetic equation, having respective initial and boundary conditions, were solved by means of numerical simulation. The finite difference method was employed to solve the resulting system of differential equations. The calculations were conducted using the RAD Studio software package. Graphical results were processed using the OriginPro software package.

Results. Scenario modeling took into account the type of forest fire, the period of the fire hazard season, forest fuel properties, the degree of the forest fuel dispersion, and the initial moisture content in a forest fuel element. The authors have found that the major influence is made by the extent of dispersion and the type of forest fire. The similarity of qualitative characteristics of sooting has also been established for all types of forest fires.

Conclusion. The proposed mathematical model can be used in conjunction with geoinformation systems to visualize the initial and output information in the process of assessment, monitoring and forecasting of forest fires and their environmental consequences.

Introduction. The authors focus on preventing the explosive spalling of concrete and the fireproofing of reinforced concrete structures. The relevance of this issue is explained by the insufficient number of fire tests of such structures under loading and thermal engineering calculations, needed for an objective analysis of testing results.

Goal and objectives. The authors analyze the results of a series of fire tests, involving concrete columns and slabs with and without polypropylene microfiber, if no fireproofing is applied, as well as the results of the same tests involving the same items fireproofed by plates or plaster.

Methods. The fire resistance of full-scale specimens of concrete was evaluated according to a standardized testing in a fire furnace under loading. It encompasses additional thermocouple measurements used to make a thermal engineering analysis. The analysis entailed both one- and two-dimensional problem formulations, methods and programmes for the numerical computation of non-stationary temperature fields in fireproof structures.

Results. New data, obtained in the course of the fire experiments, show the efficiency of the polypropylene microfiber used to prevent the explosive spalling of concrete. The fire resistance limit is R 120 and R 150 under constant static loading. The fire resistance limit of similar structures, fireproofed by PROSASK Firepanel plates or IGNIS LIGHT plaster, was demonstrated. The specimens show the efficiency of methods and programmes for the one- and two-dimensional numerical analysis of non-stationary temperature fields in fireproof structures. The calculation results are presented for various fireproofing options.

Conclusions. The testing results and their thermal analysis represent important items of information necessary to ensure the fire safety and the pre-set fire resistance of concrete structures under loading. They can also be used to outline the development pattern of this experimental and theoretical research project. The efficiency of thermal engineering calculations as a tool for evaluating fire protection parameters and the fire resistance of concrete structures is demonstrated, also as an option to reduce the number of expensive fire tests.

Introduction. The wide-scale use of catalytic converters and particulate filters in automobile engines has aggravated the problem of their ignition and updated the research and methodological framework for the examination of causes of fire emergency modes (FEMs) of operation of fuel catalytic units (FCUs). The relationship between the FEMs of the FCU operation and failures of the fuel equipment, wear of the cylinder-piston group of engines and deviations in fuel compositions was confirmed. The goal was to develop a diagnostic method for fire hazardous modes of operation of FCUs of vehicles.

Methodology. A model of oxidative catalysis underway in the FCU has been proven rational. The model is used to calculate the thermo-catalytic efficiency and heat generation in the active layer of the γ-Al2O3 platinum catalyst depending on the temperature of exhaust gases (EG), concentrations of CO, CH and soot. It has been found out that catalysis can theoretically develop in four limit domains: internal kinetic domain, internal diffusion domain, external diffusion domain, and external kinetic domain.

Results and discussion. Experimental and computational studies have shown the probability of emergence of breakdown vehicles with a multiple excess of soot emissions and thermal stresses. A 10‑fold increase in CO, CH and soot in EG rises the thermal performance of the catalytic reaction from 17,282 to 491,907 kJ/h, creating a fire hazard in a KamAZ engine. To identify a FEM, the diagnostic method based on the «free acceleration» (FA) mode according to GOST 33997–2016 is proposed. The procedure is supplemented with maximum revolutions and restrictions (0.5 s) of the FA mode time. The latter is necessary for the guaranteed operation of the engine in the «full load mode». The method was applied in the course of the fire engineering studies on a Ford Mondeo car having a TDCi (Common Rail System) diesel engine and a catalytic particulate filter. Laboratory examination and analytical studies have found that the main reason for the operation of FCU in emergency (due to environmental and fire hazards) modes is the corrosion of precision parts of the fuel equipment accumulated during its long-term operation. Progressive corrosion is caused by excessive sulfur and moisture content in fuel and oil.

Conclusions. It’s been proven that the emergency heating of a catalytic converter causes a sharp rise in the car combustion risk. The authors have proposed an original method for the diagnostics of fire-hazardous modes of operation of catalytic converters based on procedures set in GOST 33997–2016 (ТР ТС 018/2011).

Introduction. The current Russian Regulation on classification of hotels hardly takes into account their fire safety conditions. The system, adopted in the Regulation, provides for an expert scoring assessment of hotel parameters for their assignment to a certain category (star rating). The purpose of the article is to develop methods that allow determining the level of fire safety of hotels in points commensurate with the accepted rating system, for its further use in the course of assignment of appropriate categories to hotels. Theoretical fundamentals of scoring methods of assessment of fire safety of hotels. Three approaches to the calculation of «fire points» of hotels have been developed, based on the breakdown of hotels into classes and identification of the fire safety index of hotels within one class. The first scoring method is the Gretener method used for calculating the integral fire safety index. The first and third quartiles are identified for the hotel statistics. Hotels, whose index does not exceed the first quartile, belong to the subgroup featuring a high level of fire safety; those ranging from the first (inclusively) to the third quartile belong to the medium level. If the values of the fire hazard index of hotels are not smaller than the third quartile, they belong to the subgroup that has a low level of fire safety. The second method is based on the use of a «safety reserve» in terms of evacuation time. The third model of assessing the fire hazard of hotels includes the breakdown of hotels into groups, identification of the value of individual fire risk, ranking hotels by the fire risk that varies from the lowest to the highest.

Results and their discussion. As for the classification of hotels, problems that accompany the consolidation of the physical approach to the fire hazard assessment with the expert method of scoring are solved by choosing the proportion between the points of the system and the «fire points» set by the adjustment coefficient. The fire points, assigned to the subgroups of hotels, are indicative and should be corrected within the framework of the proposed approach.

Conclusions. The experimental application of the developed methods using the cases of real hotel facilities will allow choosing the optimal engineering method of taking into account the fire safety of hotels in the process of their classification.

Introduction. Methodological provisions must be developed to evaluate the impact of the fire resistance factor of building structures on human safety during evacuation and rescue with account taken of the composition andfunctional characteristics of other fire safety systems to formulate modern regulatory requirements for the fire resistance of building structures under fire conditions, develop science-based solutions for the fire safety of buildings and structures in case of forced deviations from the fire resistance requirements set in regulatory documents, and justify the construction of buildings and structures, based on modern structural systems, having non-standard fire resistance limits, etc.

The purpose of the article is to develop general methodological provisions and mathematical relationships that allow evaluating the impact of the fire resistance limits of building structures both on safe evacuation and safe rescue from buildings.

Methods. Analytical and mathematical methods are used to evaluate the combined effect of changes in the fire hazard arising along the evacuation routes, in a room with a person waiting to be rescued by fire departments, as well as along the routes taken by fire departments carrying this person out, in combination with the evaluated time span needed for the structure to lose its fire resistance. The value of this time span is used to identify the time available for the safe evacuation and rescue of people.

Results. Theoretical provisions have been developed to take into account the influence of the fire resistance factor of building constructions on the safety of people in a building in case of a fire.

Conclusions. The research findings were contributed to the general methodological provisions and mathematical relationships needed to determine the quantitative relationships between the extent of fire resistance of a building, fire resistance limits of building structures, the time of arrival of fire departments, types of fire alarm and evacuation control systems, and the possibility of safe evacuation and rescue of people from a building.

The authors have analyzed the cases of fires and explosions caused by lithium-ion batteries in the Russian Federation over the past five years. Various types of designs of lithium-ion batteries and their fire hazards are considered. A description of the process of thermal runaway in a battery and its subsequent ignition and/or explosion is provided. A generalized chart of possible causes of ignition of a lithium-ion battery, triggered by internal and external factors, is presented. Ways to reduce fire and explosion hazards during the storage, operation, maintenance and repair of battery packs are shown.