Purpose. The purpose of this work is to study the process of thermal decomposition (pyrolysis) of two samples of a hybrid organic-inorganic (OIH) heat-insulating material based on data obtained by thermogravimetric analysis and IR-Fourier spectrometry.

The goal set predetermined the following research tasks: to find out the basic chemical structure of the OIH samples (by functional groups), to study the order of processes in materials when heated in nitrogen, to calculate the activation energy, the pre-exponential factor, to determine the pyrolysis mechanism.

Methods. The methods of thermogravimetric analysis and IR-Fourier spectrometry were used in the work. Samples for spectrometric analysis were prepared in the process of thermogravimetric tests using the “freezing” experiment method.

Results and discussion. The paper studies the structural features of two samples of hybrid polyurethane inorganic (OIH) thermal insulation material and traces the physicochemical processes that occur when they are heated under dynamic conditions in a nitrogen atmosphere up to 750 °C.

The multi-stage nature of the pyrolysis of the OIH material is shown. The pyrolysis of the first sample is a threestage process. For the second sample, decomposition proceeds in two stages. All stages are endothermic. This indicates the predominance of energy costs for breaking bonds between the organic and inorganic parts and other conclusions.

It has been established that the pyrolysis of OIH samples at all stages is carried out according to the mechanism of nucleation and the growth of nuclei (active centers of destruction). Analysis of the IR spectra of the samples showed that both samples were prepared using Desmodur aliphatic isocyanates.

Conclusions. The paper studies the chemical structure and physicochemical changes when heating the new group of materials — hybrid organic-inorganic (OIH) heat-insulating materials. The article is a continuation of a team of authors systematic study of a thermal behavior of modern types of polymer thermal insulation.

Introduction. Large fires are quite often accompanied by the formation of fireballs (OSH), which create significant thermal loads. As a result of the fire coverage of a container containing an overheated liquid, a physical explosion occurs, which releases a significant amount of fuel forming a fireball. This phenomenon is dangerous because, with a short lifetime, it is capable of causing thermal injuries over considerable distances. The existing methods of predicting the consequences of a fireball, set out in various domestic regulatory documents and foreign literature, do not fully reflect the possible values of thermal loads. In this regard, a computational method for determining thermal loads was developed, taking into account the movement of the fireball.

Goals and objectives. The purpose of this study is to test the developed computational methodology for determining thermal loads, which takes into account the kinematic characteristics of the fireball. The following tasks were solved in the study:

• ● check the operability of the fireball lifting model;
• ● to conduct a comparative analysis of thermal loads according to the developed methodology with the results of calculation of domestic and foreign methods;
• ● conduct a computational experiment on the effect of air mobility (wind effect of 7 m/s) on thermal loads.

Research methods. To check the operability of the OSH lifting model, footage of the formation of a fireball was used. According to the shooting frames, the position of the fireball in space and its kinematic characteristics were tracked. Using kinematic parameters, thermal loads were determined. To assess the adequacy of calculations of thermal loads, a comparative analysis of the results of calculations of the developed computational methodology with the results of calculations using existing domestic and foreign methods was used. To substantiate the application of the developed computational methodology for determining thermal loads, taking into account the kinematic parameters of the fireball, a computational experiment was conducted using the MATLAB software and computing complex.

Results and their discussion. The results of the calculation of kinematic parameters are satisfactorily correlated with the results of mathematical modeling. The obtained values of thermal loads according to the developed computational methodology are in satisfactory agreement with the results of calculations according to existing domestic and foreign methods. Based on the calculations performed in the article, it is shown that a change in gas dynamic flows (wind demolition) leads to a significant change in the damaging factors of fireballs that are formed during fires in emergency situations.

Conclusions. The results of the research made it possible to assess the adequacy of the performance of the improved computational methodology for determining thermal loads in accidents accompanied by fireballs, as well as to justify the relevance of the application of the developed method.

Introduction. The authors have classified numerous publications, addressing the assignment of explosion and fire safety categories to premises, buildings and outdoor facilities, into the three groups: 1) sources of information that are in effect (including in-house and region-wide documents), sources that were in effect; 2) manuals and guidelines on category assignment; 3) publications that confirm (refute) or clarify some provisions, specified in regulatory sources. This article can be included into the third group of publications.

Goal. Analysis of different methods, used to identify the value of Z factor; identification of strengths and weaknesses of each method, development of recommendations on the application of these methods.

Objectives. The objective is to identify the substance-related factor contributing to explosions, use particular cases to demonstrate the efficiency of this or other identification method.

Results and discussion. The analysis of Z factor identification methods, describing the contribution of vapours of highly flammable liquids to an explosion, has proven that three types of procedures can be used to find the Z factor value:

• the method of tables (that uses the maximal possible tabular value of Z = 1; for gases and aerosols Z = 0.5; for vapours of highly flammable liquids Z = 0.3);

• the computational method based on a pattern of three-dimensional gas and vapour spreading on the premises; however, this method, if applied, may involve a high probability of errors due to numerous conditions limiting its applicability; hence, the unexplainable value of Z may exceed 1. Besides, the computational method is extremely laborious. Its application requires the clarification of conditions for its use;
• the graphical method (based on the dependency graph of Z on the X parameter). This method is the simplest and the most reliable one. When the graphical method is used to find the value of Z, the excess oxidant ratio must be taken as being equal to one, and the Х parameter must be calculated according to the following formula: Х = 0.99 Рs.v/Сst.c.

Conclusions. The graphical method, used to find the value of Z, is simple and reliable. When the Х parameter is identified, the excess air ratio is used: φ = 1.9, which leads to the underestimation of Z, the vapour-related factor contributing to explosions. To prevent the unreasonable underestimation of Z, the excess air ratio must be disregarded or taken as being equal to 0.99.

Introduction. According to statistics, the greatest loss of life from fires in Russia occurs in residential buildings with a height up to 28 m. At the same time, most fire protection systems are not provided in such type of buildings. In particular, in residential buildings of mentioned above height fire alarm system maybe not. That is why the real values of the pre-evacuation time (PET) in the buildings are not known, because domestic research still has not been conducted.

Goals and objectives. The aim of the work was to establish the values of the PET of people in a residential building that is not equipped with a fire alarm system.

The main tasks were to study the time to warn building occupants about a fire and to research the time of people’s reaction to a fire warning.

Methods. The method of scientific research in this work is a full-scale experiment. In the first set of experiments focus were on warning time — it was investigated how much time it took to warn all building occupants by 1, 2 and 3 notifiers. The second set of experiments were aimed to study of people’s reaction time to a fire alarm — it was determined how long it took to start evacuating from their apartments.

Results and their discussion. Studies have shown that the value of the alert time of a nine-storey building by one, two and three notifiers averaged was 20.0, 11.6 and 7.2 min, respectively. Based on the data obtained, a mathematical model was built that allows predicting the optimal number of notifiers depending on the number of storeys in the building. Studies of people’s reaction time to a fire alarm have shown that during the daytime, on average, people need less time to realize and prepare for evacuation (72 s) than at night (112 s). Combining the results obtained allowed us to determine the optimal number of notifiers to warn all people in residential building.

Conclusion. Comparison of the experimental values of the PET with the data of the current Methodology of fire risk calculation for a nine-storey house showed a discrepancy of 2.6 times.

Introduction. In Russia, based on the provisions of the current regulatory documents, the time for the start of evacuation for a room in which a fire broke out is determined depending on the area of the room. According to some authors, the time of the start of the evacuation of people is a combination of “technical”, which includes the time of detection of a fire, and “psychophysical”, determined by the behavioral and organizational characteristics of the people who make it up. The fire detection time is currently not taken into account.

Purpose. Evaluation of the influence of the size of the cells of the computational grid and the inhomogeneity of the computational domain on the estimated time of fire detection.

Aims. 1. Establish the qualitative nature of the influence of the size of the cells of the computational grid and the inhomogeneity of the computational domain on the estimated time of fire detection.

2. Offer recommendations for determining the estimated time of fire detection.

Methods. For research, computer simulation methods were used using the Fire Dynamics Simulator software package.

Results and discussion. The use of grids with different cell sizes can significantly reduce the number of cells in the computational domain and, as a result, the computation time. However, this leads to rather contradictory results. The minimum time values are reduced by almost 3–4 times compared to a homogeneous computational grid, and the maximum time increases by 2 times.

Conclusions. 1. The size of the cells of the computational grid and the inhomogeneity of the computational domain have a significant impact on the time of fire detection.

2. A sufficiently large spread in the values of the estimated fire detection time may indicate an unreliable estimate of the total time for the start of evacuation and incorrect conclusions about the safe evacuation of people and/or the probability of evacuation of people.

3. For a correct estimate of the evacuation start time, taken into account the estimated fire detection time, it is recommended to use homogeneous computational grids with cell sizes not exceeding 0.25 m.

Introduction. To date, fires in high-rise buildings are one of the significant problems faced by fire protection units. Unique objects require a special approach in terms of fire safety and fire extinguishing. The most important task is to ensure the supply of extinguishing agents to the height using modern fire-fighting equipment and installations.

Materials and methods. In September 2021, to conduct experimental scientific and tactical exercises on the roof of the Neva Towers tower, a program and methodology for supplying fire extinguishing agents in various ways to the height were developed. The following methods of feeding to height were considered: deployment using the equipment of a container for high-altitude firefighting, feeding from an installation with compression foam technology, feeding using a waterjet cutting unit “Cobra”.

Theoretical bases. A theoretical assessment of the possibility of supplying extinguishing agents to a height with the help of new fire-rescue equipment confirmed the need for experimental scientific and tactical exercises on the roof of the Neva Towers tower.

Results and discussions. As a result of the scientific and tactical exercises, the effectiveness of the use of new fire extinguishing systems with compression foam supply, as well as installations with waterjet cutting technology “Cobra” was proved. It was possible to provide a feed to a height of 350 m.

Conclusions. To date, with the help of new fire extinguishing technologies, it has been experimentally proven that their use is most effective compared to “traditional” methods of supplying extinguishing agents. In the future, it is necessary to conduct more detailed studies of the hydrodynamic parameters of pumping and bag systems in order to develop recommendations for preliminary planning of the actions of forces and means of fire and rescue units.

The requirements of regulatory documents on the implementation of the safe operation of batteries and rechargeable batteries are presented. A generalization of modern methods for ensuring the protection of lithium-ion batteries was carried out. Various systems of protection of single batteries for the prevention and elimination of emergency modes of operation are considered. A description of the principles of operation of protective devices and examples of their implementation in practice is given. The principle of operation of the electronic protection system in the form of small printed circuit boards built into the battery case is shown.