Introduction. The provisions of the Federal Law of the Russian Federation dated 22.07.2008 No. 123-FZ “Technical Regulations on Fire Safety Requirements” stipulate the possibility of designing L1 type stairwells with open doorways in external walls. The requirements of regulatory documents stipulate the necessity of calculation substantiation of design solutions to exclude blocking of stairwells by fire hazardous factors spreading along the facade. To test and analyze these requirements, this paper assesses the influence of different factors on the time of blocking of such stairwells by fire hazardous factors.

Goals and objectives. The purpose of this paper is to approve and analyze regulatory requirements for the protection of stairwells with open doorways from blocking by fire hazardous factors depending on the wind speed, the functional fire hazard class of the burning premises, the dimensions of partitions and projections of the stairwell, as well as the design of the windows of the burning premises.

Methods. Calculations of time intervals of stairwell blocking by fire hazardous factors spreading along the facade from the windows of burning premises were based on methodological provisions and mathematical models used to determine fire risk.

Results. The calculated data allowing to estimate time intervals of blocking stairwells with open doorways in external walls by fire hazardous factors depending on the wind speed in the area of object location, peculiarities of combustible load in the burning premises, sizes of partitions and projections of the stairwell, as well as the design of windows of burning premises were obtained. These data made it possible to assess the necessity of specifying regulatory requirements.

Conclusions. Based on the research, calculated data for formation of necessary practical experience of substantiation of the requirements on exclusion of stairwells blocking with open doorways by fire hazardous factors that spread along the facade from the windows of burning premises are received. The obtained data make it possible to evaluate the influence of wind speed, the functional fire hazard class of burning premises, the size of the stairwell projection on the time of its blocking by fire hazardous factors, as well as to determine the directions of specification of regulatory requirements.

Introduction. This paper is devoted to the issues related to calculations of gas-dynamic flows arising during emergency explosions. The relevance of this publication is due to the following circumstances. The dynamic parameters of explosive loads have a rather wide range, which varies in duration and intensity from several milliseconds and hundreds of atmospheres to several seconds and several percent of the atmosphere, which is determined by the type of explosive phenomenon. In this regard, the overall picture of destruction or post-accident situation varies significantly depending on the parameters of the explosive load, which depends on the type of emergency explosion. Based on the general picture of destruction, it is possible to determine the type of emergency explosion, for which the parameters of the gas-dynamic flows that accompanied the emergency explosion can be determined by calculation. This makes it possible to reconstruct the scenario of the emergency explosion, and sometimes the scenario of the entire accident.

In the present paper using the example of an analysis of the accident consequences and the performed calculations of the gas-dynamic flows formed during the emergency explosion, the scenario of the emergency situation development is reconstructed, which allows to speak about the causes of the collapse of building structures that occurred as a result of the accident, and about the degree of guilt of the witnesses of the accident.

Materials and methods. A brief description of the calculation methods that makes it possible to calculate the explosive pressure fields formed during the emergency explosion is given. A brief description of the methods developed by the author for calculating gas-dynamic flows accompanying the emergency explosion is given.

Research results. The results of physical modelling of local deflagration explosions in premises, performed in the laboratory of the university of civil engineering, are reviewed and analyzed. An analysis comparing the calculation results with experimental data is carried out. The results of calculation of explosive pressure parameters and gas-dynamic flows accompanying a real emergency situation are presented. The calculation results made it possible to reconstruct with sufficient accuracy the scenario of the accident development accompanied by the explosion.

Conclusions. It is shown that the developed mathematical models quite accurately describe the field of explosive pressure and gas-dynamic flows created by emergency explosions. Calculation of gas-dynamic flows accompa­nying the emergency explosion makes it possible to reconstruct the scenario of its development. The main features and difficulties arising during mathematical modelling and experimental studies of explosive loads formed during emergency explosions are described.

It is shown that for the correct prediction of loads that are realized during emergency explosions, it is necessary to model physical processes clearly and correctly and to consider scenarios of development of an emergency situation that most adequately correspond to the considered object and the surrounding buildings.

The results of calculation of explosive pressure parameters and gas-dynamic flows accompanying a real emergency situation are presented. An example of reconstructing the development scenario of the explosive accident is given.

Introduction. The results of research of thermoplastic polymeric materials of different chemical nature (high-­density polyethylene, polycarbonate, polyvinyl chloride), capable of melting, spreading, burning and dripping when exposed to high fire temperatures, forming secondary fire centers, are presented. The relevance of application of a highly accurate and informative method of synchronous thermal analysis to determine the chemical nature of polymers in fire conditions is substantiated.

Goals and objectives. The purpose of the research was to assess the possibility of application of the method of synchronous thermal analysis to identify polymeric materials with different degree of thermal impact on them when diagnosing the formation of secondary fires within the framework of fire-technical expertise.

To achieve the goal, the following tasks were solved: thermoanalytical characteristics to identify semi-crystalline thermoplastics in the native state and exposed to high-temperature effects of fire were determined; thermoana­lytical characteristics to identify amorphous polymeric materials with different degrees of thermal impact on them were determined.

Methods. The method of synchronous thermal analysis, including: thermogravimetric analysis, differential thermo­gravimetry and differential scanning calorimetry was used in the study. An example of combining the method of synchronous thermal analysis with the method of quadrupole mass spectrometry to solve the problem of identification of thermoplastics is presented.

Results. The regularities of thermal and thermo-oxidative degradation of polymeric materials were studied. The methodology of identification thermoplastics by the method of synchronous thermal analysis is considered. It was established that for polymers with exposure temperatures up to 300 °C, significant information about the chemical nature of the polymer is provided by the values of phase transition temperatures (melting, glass transition, thermal (thermo-oxidative) degradation). Determination of the chemical nature of thermoplastics with a high degree of burn-up is possible only in the presence of extrema in the curves of differential thermogravi­metry and differential scanning calorimetry in the high-temperature range of polymer thermolysis. The possibility of identification of thermoplastics by combining thermal analysis with mass spectrometry is demonstrated.

Conclusions. The analysis of research results has shown that the significant thermoanalytical characteristics for identification of semi-crystalline thermoplastics are the melting temperature and the temperature of the maximum mass loss rate of the process of thermal or thermo-oxidative degradation of the polymer. For amorphous thermoplastics — the glass transition temperature and the temperature of thermo-oxidative degradation of the polymer.

Introduction. During natural aging, processes occur in cellulosic materials that lead to changes in properties and transformation of the material structure. The study of physico-chemical transformations in naturally aged paper, their influence on thermal stability and fire hazard properties of the material is limited.

The aim of the research is to establish the physico-chemical properties and thermal stability of naturally aged paper.

Objectives:

• to study the physico-chemical properties of paper of different period of publication (1946–2020);
• to evaluate the thermal characteristics of paper by thermal analysis methods with the establishment of kinetic parameters of the thermal decomposition process, as well as the characteristics of heat release.

Research methods. The research was carried out for paper specimens of different year of publication (1946–2020). Bruker FT-IR spectrometer and thermal analysis methods were used for the research.

Results and their discussion. According to the results of the study it was found that in the process of paper aging hydrolytic destabilization products of lingo-carbohydrate components are formed with disturbance of morpholo­gical structure of the material (density reduction up to 20 %).

In pyrolysis for naturally aged paper, a shift of the maximum decomposition rate plot to the low-temperature region was found. The largest decrease in activation energy (up to 450 °C) was obtained for 1946 paper (Ea = 92.9–185.8 kJ/mol). Thermal oxidative decomposition of naturally aged paper at the 160…450 °C stage is characterized by a more significant mass loss (up to 48 %). The extension of temperature limits of the stage of oxidation of carbon residue for pyrolysis up to 35 % and for thermal oxidative decomposition up to 45 % was established, which contributes to the increase of total heat release up to 47 %.

Conclusions. The results indicate a significant loss of chemical and thermal stability of paper as a result of natu­ral ageing with the progression of hydrolytic destabilization of the lingo-carbohydrate complex. Physico-­chemical changes characteristic for paper of natural aging, violation of its morphological structure were established. The stage of oxidation of the carbon residue is characterized by the expansion of the temperature limits of the oxidation reaction, which has a significant exothermic effect.

Introduction. Upholstered furniture occupies quite a significant area of the premises of many public buildings. During its combustion, mixtures of toxic gases can be formed, the quantitative and qualitative composition of which is unknown. Therefore, obtaining experimental data on the toxicity of upholstered furniture is an urgent task.

Goals and objectives. Experimental determination of flammability and toxicity parameters of combustion pro­ducts of upholstered furniture elements necessary for calculation of the time of blocking of evacuation routes in buildings.

To achieve this, experimental studies of specimens of upholstered furniture elements were carried out on standard installations, as well as on the installation for determining the fire hazard of condensed substances and materials.

Research methods. Standard methods for determining the flammability of decorative fabrics (GOST R 50810–95), the flammability of upholstered furniture elements (GOST R 53294–2009), the toxicity index of combustion pro­ducts (GOST 12.1.044.89, paragraph 4.20) and the method for assessing toxic gas concentrations at a small-scale experimental installation to determine the fire hazard of condensed substances and materials were used.

Research results and their discussion. The determination of flammability of materials and compositions of upholstered furniture products, as well as the assessment of the toxicity of the gaseous atmosphere during their thermal decomposition in a small-scale experimental installation allowing the measurement of concentrations of toxic gases, were performed. Experimental studies were carried out to study the toxicity parameters of the most dangerous gases formed during the combustion of a number of specimens of upholstered furniture elements.
It was revealed that during the combustion of upholstered furniture elements, such highly toxic gases as hydrogen cyanide and carbon monoxide are emitted in concentrations dangerous to human life and health.

Conclusions. New experimental data on specific mass rate of burnout velocity, as well as numerical values of specific coefficients of carbon monoxide and hydrogen cyanide formation of upholstered furniture elements have been obtained, which will allow to expand the existing database of typical fire load in building premises.

Introduction. According to the information of the Ministry of Labour and Social Protection of the Russian Fede­ration, the most common type of accidents with injuries and fatalities at work is a fall at different heights. The analysis of such accidents for 2022 and 2023 by types of economic activity shows that the largest number of accidents with severe consequences occurs in construction.

Purpose of the work. To ensure the safety of people with the help of personal protective equipment (PPE) when performing work at a height in the construction industry.

Objectives. Analysis of scientific works devoted to the influence of light and weather on textile protective equipment. Analysis of the group of GOSTs regulating the certification of PPE against falling from a height for the presence of technical requirements and methods of testing textiles and paint coatings for the impact of light and weather, including solar radiation; problem statement and development of recommendations for further work in this direction.

Analytical part. The safety of application of textile personal protective equipment against falling from a height as one of the most widespread types of protection at the construction site, which are exposed to the impact of light and weather, is considered. The analysis of scientific and technical sources shows that exposure to light (especially ultraviolet), as well as the combined effects of light, temperature, humidity and other atmospheric conditions leads to the degradation of textile PPE. On the basis of the complex analysis carried out in the paper, the conclusion is made about the need for normative regulation of this area of textile PPE in the field of technical requirements and test methods, as well as the need for additional parameter-oriented research in this direction.

Conclusions. Published sources do not contain information on light and weather resistance of textile PPE. The analysis of published studies indicates the negative influence of atmospheric conditions on textile and poly­meric materials. The necessity of development of test methodology and balanced requirements to the material resistance to light and weather impact is determined, as the existing GOSTs in the field of PPE against falls from a height do not apply to these textile PPE and have functionally unoriented criteria for determining the negative impact of light and weather.

Introduction. The Government of the Russian Federation set a task to reform the traditional model of occupational safety management and create a modern occupational safety management system (OSMS) based on the implementation of practical procedures that are characterized as “occupational risk management”.

Methodology. In modern conditions, the concept of “acceptable risk” is used in practice. Occupational risk management is a cyclical sequence of interrelated practices known as the “Deming – Shewhart cycle”.

Results and their discussion. The functioning of the new OSMS model facilitates the transition from the practice of responding to the facts of occupational injuries and occupational diseases that have already occurred to the mechanism of developing and implementing preventive measures to prevent accidents and preserve the health of the labour collective. As part of the implementation of reform tasks, the country has developed and adopted a number of regulatory and legal documents that contain recommendations for the introduction of a modern system for the prevention of occupational injuries and diseases based on occupational risk management techniques.

Conclusions. Despite the efforts of state structures and public organizations, the process of reforming the occupational safety management system at enterprises is slow or formal, not affecting the main content of the modern model of labour protection. Undisclosed or concealed facts of incidents reduce the volume of information for analyzing the real situation ten times and significantly reduce the effectiveness of work on occupational risk management.

Introduction. Such a definition as “fire rank” is used in the practice of fire respond and elimination management for quite a long time and has several meanings, the main of which are two: to show in detail the degree of complexity of the fire based on the fire rank, to allocate an adequate number of different types of resources for its successful elimination. The chain of elements: fire — degree of complexity — necessary resources, has not yet been embodied in effective methods and regulatory documents, which gives relevance to this area of research.

Goals and objectives. The purpose of the paper is to build a technology for constructing models of fire ranks based on the use of cluster analysis. The tasks include exploratory data analysis and construction of a stochastic model of fire ranks.

Methods. The study used methods of mathematical statistics and unsupervised machine learning in the variant of cluster analysis.

Results and discussion. The possibility of determining a grid of fire ranks and the corresponding number of allocated vehicles based on processing by cluster analysis methods of a selection of retrospective data is shown. It is shown that the obtained results are very close to the norms of allocation of vehicles for fires in Moscow. The concept of stochastic fire ranks as a more informative model for resource allocation is put forward.

Conclusions. The presented results of solving the problem of identifying a grid of fire ranks using a selection of retrospective data make it possible not only to determine the amount of resources required to eliminate a particular fire, but also make it possible to build adaptive stochastic models of fire ranks that are adequate to the region, industry and other subsets of fire objects.

Generalized data on fires in the world involving electric vehicles are presented. Some examples of fire hazardous situation development when using charging stations without inbuilt protection systems are considered. A method of fire risk assessment in enclosed surface and underground car parks with the availability of parking spaces for charging electric vehicles is shown. Explanations on the peculiarities of preventing and extinguishing fires involving an electric vehicle or charging station are given. One of the examples of performing a fire risk assessment based on the ERIC index method is analyzed with the indication of measures to eliminate and mitigate the consequences of a possible fire in the types of car parks under consideration.