Introduction. In recent years, much attention has been paid to the risk-based approach in the field of fire safety and, in particular, the calculation of fire risk has been widely used. The approaches and methods of such calculations have become considerably more complicated. However, the presence of a number of problems indicates the need to limit the use of fire risk calculation and optimize it, taking into account the prevailing realities of practical application.

Goals and objectives. The purpose of the paper is to identify existing problems in the calculation of fire risk and their impact on the results of such calculations, including the correctness and possibility of applying design solutions that they justify. In addition, one of the tasks is to find ways to optimize and simplify the calculation in order to reduce the time and material costs of its implementation, high-quality verification by regulatory authorities while maintaining the necessary accuracy of the engineering assessment.

The main part. The normative bases and prerequisites for the emergence of computational methods for assessing fire risk are considered. The existing problems of modern application of such calculations are described, including inconsistencies and distortions in the regulatory field, the lack of necessary elements of compliance with the concept of correct assessment (result error, lack of rules in the field of software products and qualifications of specialists, etc.), the lack of verification and, as a result, the inability to assess the correctness of design decisions made in accordance with the calculation. Approaches for optimization of calculations are proposed. A model of evacuation of people is described and a computer programme for its implementation is tested. The calculation of the model object is performed.

Conclusions. The problems described in this paper indicate a significant imperfection of the fire risk calculation tool, which, in turn, does not allow it to be used to justify many design solutions that are currently justified by such a calculation. At the same time, the corresponding calculation methods should develop not only along the path of complication, but also have the possibility of optimization in terms of practical application and verification of calculation results. In addition, taking into account the current situation, it is natural to limit its application for a number of cases, at least until the necessary accuracy is achieved, or appropriate legal mechanisms are developed that allow neglecting the presence of a large error and regulating the scope of application of techniques, software and the work of relevant specialists.

Introduction. Using relief structures to reduce pressure in case of an indoor explosion is widely spread. Moreover, it is legitimized by regulations. However, regulatory documents ignore the well-known fact that the embedment depth of relief structures is equal to or exceeds the value of their thickness. As of the moment when the relief structure begins to move after the disintegration of its bonding from the frame and up to the moment when it leaves the opening, explosion pressure may rise exponentially.

Goal. The goal is to determine the effect of embedment depth of a relief structure on the pressure rise during an indoor explosion at the initial stage of explosion development when the relief structure moves in the opening.

Research methods. The experiment was conducted in a blasting chamber with an opening door where the model of a relief structure was installed.

Results and discussion. The authors found that, if the chamber remained hermetically sealed, the explosion pressure increased proportionally to t3, at least, up to ΔP < 10 kPa. In case of free motion of a relief structure in the opening, the tightness of the system degraded as the explosion developed. As a result, the relief structure left the opening if the pressure value was below that identified as a result of calculations made for conditions of tightness. Nevertheless, an increase in pressure, even in case of poor tightness, followed a change in dimensionless parameter B, which determined the process at this stage of explosion development.

Conclusions. The process is controlled by dimensionless parameter B. The quantitative difference is triggered by the system tightness loss, accompanying the pressure rise, and emergence of the friction force accompanying the attempt to hermetically seal the system. These two circumstances reduce the relative explosion pressure rise, while the relief structure is in motion in the opening if the friction force is taken account of in the course of identifying the value of pressure at which bonding between the relief structure and the building are disrupted.

Introduction. The “overdrive” effect is well known, when dust/air mixture, explosive during testing in a 20 L chamber, turns out to be safe according to the results of more reliable testing in a 1-m3 chamber. The overestimation of the dust explosion hazard in the 20 L chamber is explained by the preheating of the fresh dust/air mixture with the flame of an energy-intensive (Eig) ignition source. The possibility of “overdrive” is judged by the following basis: at Eig = 10 kJ, the explosion index Kst < 4.5 MPa∙m/s (Proust et al., 2007). This paper is devoted to the identification of additional signs of “overdrive” in the 20 L chamber using the example of non-explosive anthracite to reduce the probability of the above-mentioned qualitative error.

Analysis of publications. The random nature of anthracite explosiveness over a wide range of dust concentrations at Eig = 5 kJ was observed (Cashdollar, Chatrathi, 1993). Two inflection points on the ascending branch of the dependence of the anthracite explosion pressure P on time t are observed, corresponding first to the minimum and then to the maximum dP/dt, respectively. All these features may be signs of “overdrive” after experimental testing.

Anthracite and its research method. Anthracite with the volatile content of 2.7 % wt. was studied in a 20 L. Siwek chamber, Eig = 10 kJ, with video recording of radiation through an observation window.

Results. Time dependences of the medium radiation intensity and the pressure in the chamber on time in the range of dust concentrations from 125 to 750 g/m3 are obtained.

Discussion and conclusions. Three additional signs of the “overdrive” effect for anthracite were confirmed experi­mentally and proposed: probabilistic nature of the explosion hazard; two inflection points on the ascending branch of the graph P(t); noticeable weakening of the medium radiation after the ignition source burnout and before reaching the lower inflection point. The explosion pressure exceeded 400 kPa and was mainly caused by the burning of fixed carbon.

Introduction. Fire protection of metal structures is one of the urgent problems of increasing fire resistance of structures, for which purpose intumescent type materials are currently used, which have a limited service life.
At the same time, technical documentation on fire protection means has no data on the preservation of properties of the created fire protection system depending on the terms and conditions of operation. The aim of the study is to approve the method of thermomechanical analysis to assess the preservation of fire protection properties of the fire protection system during its operation.

Theoretical foundations. In modern conditions, experimental assessment of the preservation of properties of fire protection means, as a rule, is not carried out, the manufacturer is limited to conducting tests to determine the values of fire protection effectiveness of fire protection means, which contradicts the requirements of national standards. At the moment, there are no standardized test methods for the preservation of fire protection properties of fire protection means depending on the terms and conditions of operation in our country.

Methods. Optimal parameters for testing fire protection products using the thermomechanical analysis (TMA) method were determined, and changes in fire protection products subjected to climatic aging were investigated. The authors suggest using of universal parameter with accurate physical explanation — the coefficient of volumetric expansion, instead of rather subjective and inaccurate parameter — the swelling coefficient.

Results and discussions. Specimen aging process demonstrates significant changes in the coating, for example heat-protective foam layer formation, which leads to the situation when fire protection system is not effective in ensuring required fire resistance limit under operating conditions. The coefficient of volumetric expansion for the specimen with climatic aging is reduced by more than 40 % when used for six or more years.

Conclusions. The study demonstrates that heat-insulated layer of a fire-retardant coating during operation for more than three years is significantly reduced. The use of thermomechanical analysis method can serve as an additional proof for the effectiveness of fire protection product, both within the framework of construction control and real operating conditions.

Introduction. According to the current methodological recommendations in the field of design and calculation of parameters of smoke protection systems for buildings and structures, both in Russia and other countries, to determine the flow rate of smoke emitted during a fire in the premises, which must be removed by exhaust smoke ventilation systems, dependencies based on the thermal power of the fireplace are used fire. The process of smoke formation in a room and its rate during a fire, in addition to the lower calorific value and specific burnout rate, can be affected by such characteristics of the fire load as smoke-forming ability, the release of toxic combustion products, etc.

Goals and objectives. The purpose of the work is to verify the assumption about the influence of fire load cha­racteristics, which are not included in the value of the thermal power of the fire centre, on the process of smoke formation in the room.

Research methods. To assess the smoke content of premises during a fire, taking into account various types of fire load, computer modelling methods were used using the Fire Dynamics Simulator software package.

Results and its discussion. The results of modelling the dynamics of temperature, density and smoke visibility in rooms with an area of 100 and 200 m2 during a fire are presented, taking into account various types of fire load involved in combustion.

Conclusions. Qualitative differences in the time from the beginning of the fire to the loss of visibility, the dynamics of the optical density of the smoke-gas-air environment, as well as differences in the area of smoke in the premises indicate a significant differentiation of the process of smoke in the premises depending on the properties of the combustible load involved in the fire.

The identified influence of the characteristics of the fire load, which are not included in the thermal power of the fire source, on the process of smoke formation in the premises requires additional research to assess the efficiency of smoke removal systems from the premises, taking into account the results obtained in this paper.

Introduction. The paper substantiates the importance of investigations into the behaviour of tanks with compressed and liquefied hydrogen in the body of the fire due to the fact that such accidents at hydrogen transport facilities are the most dangerous. The relevance of the paper is conditioned by the need to analyze such scenario of the accident to prevent it and to reduce its consequences. The aim of the paper is to analyze the regularities of such accidents on the basis of consideration of modern research in the specified direction.

Behavior of tanks with compressed hydrogen in the body of the fire. Compressed hydrogen is usually stored in composite cylinders, while liquefied hydrogen is stored in double-shell isothermal tanks. When the cylinder made of composite materials with compressed hydrogen gets into a fire, it explodes within 5–15 minutes if no fireproofing is made for these cylinders. A destruction of the cylinder made of the composite materials takes place at gas pressures exceeding an initial pressure not more than on 10 %. A rupture occurs due to a loss of polymer compound. A fire resistance limit of such a cylinder is inversely proportional to an intensity of thermal action of the fire.

Behavior of tanks with liquid hydrogen in a fire. Liquid hydrogen is stored and transported in double-shell isothermal tanks. The fire resistance limit of the liquefied hydrogen tank can reach several tens of minutes depending on the parameters of thermal isolation.

Conclusions. Shock waves, fireballs and fragments of the tanks are the main hazardous factors of the accidents with a rupture of the hydrogen tanks. Sizes of hazardous zones can reach several tens of metres, depending on the para­meters of cylinders and tanks. The largest size of the affected zone was observed in the case of the fireball formation. The fire resistance limit of the tanks is inversely proportional to an intensity of the thermal action of the fire.

Introduction. In this paper, theoretical and practical aspects of application of Markov chains to modelling of functioning of systems of fire protection of objects on the example of automatic fire extinguishing systems are considered.

Materials and methods. In the process of work, the mathematical apparatus of Markov chains was used and relevant theoretical information was provided. An automatic fire extinguishing system is used as an example and a graph of its states is given, with the help of which it becomes possible to describe theoretically and quantitatively estimate the probabilities of the installation states. The possibility of optimization of such a graph is shown.

Theoretical basis. Determination of probabilities of the conditions of the system under study (in this case, an automatic fire extinguishing system) during operation — readiness mode, temporary shutdown, operation, restoration of readiness and testing, which allows both to assess the effectiveness of its application and to develop the necessary recommendations to improving efficiency.

The results and their discussion. As a result of the study, mathematical expressions and quantitative estimates of the probabilities of the states of an automatic fire extinguishing system were obtained, on the basis of which proposals can be formulated to improve the efficiency of its functioning. Using the optimized Markov chain graph, an analytical expression for estimating the dynamics of the state probability of readiness to use of an automatic fire extinguishing system was obtained.

Conclusions. Using the example of the operation process of an automatic fire extinguishing system, the paper shows the possibility of describing it using a semi-Markov chain in order to assess the probabilities of installation conditions. The possibility of optimizing the chain in order to simplify it and obtain analytical expressions of the dynamics of the probabilities of states is also shown. The presented approach can be used by other researchers to solve similar problems.

Introduction. Advanced technologies, integrated into automatic fire fighting systems, are vital for prevention and fast detection of fires. Non-functional or malfunctioning equipment and technology often become the main cause of fire. However, trends in intelligent fire detectors enjoy insufficient attention of domestic authors. Therefore, the article focuses on this issue. Relevant tasks are solved to study automatic fire fighting systems and the role of detectors in their operation, to identify the main areas of research addressed by relevant domestic and foreign publications. The availability of accurate values and adjustability of parameters ensure high process safety and a good response time, if needed.

Analysis. Intelligent detectors, taking advantage of such tools and technologies as machine learning and electronic nose, their application in fire hazard detection are considered. Diagrams and data, describing the use of fire detectors, are presented. Different levels of safety conditions are analyzed. Methods for converting signals, coming from detectors, as well as options for integrating electronic nose techniques and thermal imaging cameras into automatic fire fighting systems are proposed. In addition, authors emphasize the benefits of electronic nose, machine vision, and micro-sensor clusters in fire safety assurance.

Conclusions. Intelligent fire detectors skyrocket the efficiency and reliability of automatic fire fighting systems. The authors’ findings will be helpful for researchers, engineers and designers of automatic fire fighting systems, students majoring in 20.03.01 Technosphere Safety, 27.03.01 Standardization and Metrology, students majoring in 27.04.02 Intelligent Measurement Systems for Quality Management, Quality Control and Product Certification.

Introduction. Tactical aspects of combat action management for aircraft fire extinguishing in case of fire inside the fuselage are considered. The author’s tactics of aircraft fuselage fires extinguishing using modern equipment in service with the State Fire Service units are proposed.

Goal and objectives. Optimization and improvement of management solutions for the elimination of emergency situations of aircraft accidents, as well as improvement of staffing and equipping of fire and rescue units.

Materials and methods. In the process of work the tactics used today to extinguish such fires by emergency rescue units were considered, as well as fire-tactical exercises to extinguish an aircraft on the territory of an international airport were carried out. Two calculations of combat operations on extinguishing fires with the use of available forces and means of rescue units were made: the calculation of the actually used extinguishing tactics and the calculation of the extinguishing tactics proposed by the authors of the paper after approbation of it during the exercises. In conclusion, a comparative analysis of the data obtained from the calculations is made.

Results and their discussion. As a result of the research, the author’s tactics were proposed, based on the application of modern technology designed for rapid fire extinguishing, namely, fire extinguishing installations with waterjet cutting “Cobra”. Based on the calculations made, comparative analysis and conclusions obtained, the authors of the paper recommend supplementing the units of search and rescuing services of our country’s flights with fire extinguishing installations with waterjet cutting “Cobra”, which are currently not available to these services.

Conclusions. As a result of the research a reasonable conclusion about the effectiveness and necessity of implementation of new tactics of fire extinguishing and additional staffing of the services of search and rescue support of our country’s flights with fire extinguishing units with waterjet cutting “Cobra” was obtained. Also, in the absence of graphical representation of the fire extinguishing installation with waterjet cutting “Cobra” in the regulatory documents of the EMERCOM of Russia, the authors of the paper developed and proposed to use in the pre-planning documents a graphical representation of the fire extinguishing installation with waterjet cutting “Cobra”, and to make changes in normative base of the EMERCOM of Russia in the form of graphical representation of this installation, as at present it is absent.