Fire Extinguishing Research Articles

О НОВЫХ ПОДХОДАХ К СОЗДАНИЮ ВЫСОТНО-СПАСАТЕЛЬНЫХ АВТОМОБИЛЕЙ НА СОВРЕМЕННОМ ЭТАПЕ

Information is provided on the development and production of high-altitude rescue vehicles at the present stage, as well as on the transition of domestic standards to the international standardization system within the framework of the states belonging to the Commonwealth of Independent States. The differences between the requirements of modern standards for fire ladders and car lifts, which come into force in Russia on July 1, 2024, and those in force, are considered. The analysis of modern terminology in the design and operation of fire ladders and car lifts, new approaches to some of their parameters, as well as the introduction of additional parameters is given. The requirements for the chassis that ensure the prompt departure of high-altitude rescue vehicles to the place of fire (accident), the conditions for ensuring cargo static and dynamic stability when applying fire extinguishing agents, the need for equipment with control devices and pointers in connection with the use of computer technologies in their control systems have been formed. The technical solutions for providing modern fire trucks with automatic boom stage alignment systems are analyzed, promising approaches to creating boom stage alignment systems are substantiated. The conclusion is made about the compliance of modern high-altitude rescue vehicles with the requirements of Interstate standards.

Evaluation Indicator for the Spontaneous Combustion of Biomass Fuel Pellets and Its Self-Ignition Control

ABSTRACT To investigate the spontaneous combustion characteristics of biomass fuel particles, spontaneous combustion processes of 10 biomass samples were simulated by programmed-heating and continuous oxidation experiments. Analysis results indicated that during the very initial stage of spontaneous combustion (<90 °C), each biomass fuel particles merely yielded CO at 0–20 ppm, while the subsequent exponential growth of gas emissions tended to exhibit a significant variation on spontaneous liability. Due to the diversity of biomass material sources, its spontaneous combustion tendency is not only determined by internal properties, but also influenced by external factors such as particle size, ventilation rate, moisture, etc. There are many factors affecting the spontaneous combustion tendency, which cannot be analyzed accurately and quantitatively. Therefore, it is necessary to propose a stable indicator based on thermal analysis to objectively evaluate the tendency of biomass spontaneous combustion. A scientific index was proposed to precisely assess the spontaneous combustion tendency of biomass materials. Specifically, the activation energy (E) at the O2 gain stage was adopted as the priority criterion: If E < 70 kJ/mol, the biomass was defined to be highly flammable; if 70 ≤ E ≤ 80 kJ/mol, the biomass was considered to be prone to self-ignition; and if E > 80 kJ/mol, the biomass was regard as non-spontaneous combustion. Besides, data from cross-point temperature tests fundamentally support the reliability of mentioned evaluation methodology. In fire-extinguishment experiments, a conventional approach, such as suffocate by self-extinguishing, only reduced the temperature to 99.9–238.7°C. The comparison of extinguishing materials such as gaseous N2/liquid nitrogen, CO2, and C3HF7 revealed that extinguishing fire with C3HF7 exhibited a dramatic advantage at burning temperature > 500°C. However, fire extinguishing with CO2 was more suitable for the spontaneous combustion ignition of biomass at temperature ≤ 300°C.

Perancangan dan Penempatan Alat Pemadam Kebakaran Jenis Sprinkler

The fire suppression ability of this sprinkler installation compared to other fire extinguishing equipment has been proven to be more effective. Because the sprinkler system does not require an operator when operating, fires can be prevented earlier before causing greater losses. For this reason, the implementation of sprinkler systems in buildings is crucial. According to KEPMEN PU NO. 10/KPTS/2000, a building must have elements that can maintain structural stability to a certain level during a fire. This research was conducted directly in the field, and the necessary data was obtained independently through interviews with relevant parties. The author conducted research observations in the archive warehouse to obtain both primary and secondary data. Primary data included field documentation and calculations. Planning calculations were done directly by calculating the number of sprinklers, water requirements, and reservoirs to determine the precise needs. Based on the survey, it was found that the size of the archive warehouse is 48 x 48 m, totaling 2304 m2. The maximum distance between sprinklers used was 4.6 m. Therefore, the effective distance between sprinkler heads is 193 units. The result of the calculation for the water supply for the sprinkler system obtained 34,139.77 liters, with the total overall cost for the equipment and materials used being Rp. 63,121,925.74. Based on the data and calculation results regarding the planning and design of fire protection equipment in open active spaces adhering to the NFPA-13 Standard for the Year 2019, it is expected to provide comfort and safety against the threat of fire incidents.

Inhibition effect and extinguishment mechanisms of YS1000 microemulsion for lithium iron phosphate battery fires

The inhibition of Lithium ion battery (LIB) fires has attracted more and more attention from the public. However, an effective fire-extinguishing agent used for LIB fires has not been reported. The use of water mist containing additives for LIB fires is a promising method. In this work, the YS1000 microemulsion was prepared. A fine water mist fire extinguishing system was established to study the extinguishment efficiency of the fire-extinguishing agents for LIB fires. The fire suppression efficiency of pure water, F-500 fire extinguishing agent, and YS1000 microemulsion for the 32135-type lithium iron phosphate battery (LFP) were compared in this paper. The fire extinguishment mechanism of YS1000 microemulsion was revealed by thermo gravimetry, differential scanning calorimetry, mass spectrometry (TG-DSC-MS) combined technology. The results showed that it took more than 30 s for pure water to extinguish the LFP fire. In the case of pure water, three batteries went into thermal runaway (TR). It only took less than 1 s for YS1000 microemulsion to extinguish the fire. In the process of extinguishing the fire, only one battery experienced TR. Compared with pure water, the total heat dissipation of YS1000 microemulsions to the batteries increased by 79 %. The YS1000 microemulsion extinguished the LFP battery fire mainly depending on phosphoric acid decomposing product of YS1000 microemulsion at high temperature. The phosphoric acid could eliminate H∙ and OH∙ free radicals in the flame. Research results are expected to provide a significant reference for the design of fire-extinguishing agents used for LIB fires.

Computational Approach for Architecture, Tailoring, and Advancements in Perfluorinated Compounds: Synthesis, Characterization, and Future Directions in Fire Suppression Technology

The demand for effective fire extinguishants has spurred investigation into novel perfluorinated molecules due to their exceptional properties, including high thermal stability, low toxicity, and eco-friendliness. This study presents a computational framework for designing and tailoring perfluorinated compounds as potential alternatives to traditional extinguishing agents. The research centers on elucidating the synthesis, molecular architecture, and characterization of these compounds to enhance their fire suppression capabilities while mitigating environmental impact. By employing computational methods, molecular modeling, and advanced spectroscopic techniques, the structural intricacies and potential applications of perfluorinated compounds in fire suppression are investigated. Additionally, future research directions aimed at addressing challenges and advancing the development of environmentally sustainable fire extinguishants are discussed. This manuscript contributes to the ongoing efforts to replace conventional extinguishing agents with safer and more environmentally friendly alternatives.

Molecular simulation of competitive adsorption of CO2/N2/O2 gas in bituminous coal

The main cause of coal spontaneous combustion is the oxidation and temperature rise of coal. Injecting composite inert gas for fire prevention and extinguishing is one of the important methods to prevent coal spontaneous combustion. A large number of studies have macroscopically investigated the fire prevention and extinguishing effects of CO2/N2 and their synergistic actions. However, there is currently a lack of research at the molecular level on the competitive adsorption mechanism between mixed inert gases (CO2, N2) and O2 molecules in coal. Therefore, this study conducted adsorption experiments using Qian Yingzi(QYZ) bituminous coal and compared them with the simulation data of the Wiser coal model to verify the reliability of the Wiser model. Subsequently, employing grand canonical Monte Carlo (GCMC) and molecular dynamics (MD) methods, the competitive adsorption behavior of different proportions of binary mixed component gases (CO2/O2, CO2/N2, O2/N2) at a temperature of 303.15 K was investigated from five perspectives: adsorption capacity, adsorption selectivity coefficient, potential energy distribution, competitive adsorption heat, and interaction energy. The results indicate that among the competitive component gases, CO2 exhibits the strongest adsorption effect on the entire system, which is closely correlated with the distribution range of adsorption energy sites. The adsorption heat and adsorption amount of CO2 consistently exhibit a negative correlation, whereas the relationship between the adsorption heat of N2 and O2 and the adsorption amount shows a positive correlation. Their adsorption capacities depend on the pressure and the proportion of the two gases. Based on the isothermal adsorption curve of CO2/N2, it is recommended that the gas pressure during actual inert gas injection be less than 2.5 MPa. Under this pressure, the competitive adsorption effect is no longer significant, providing a certain theoretical basis for high-pressure injection. Moreover, the preliminary determination of the optimal injection ratio range is from 4:6–3:7. Furthermore, a systematic logical framework for selecting underground inert gas composition is proposed, and an underground mobile inert gas infusion process is adopted. The actual gas composition for infusion is determined based on cost factors in practical engineering. The research results can provide guidance for the selection of gas injection parameters for mixed inert gas fire prevention and extinguishing in goaf.

Low-Carbon Emissions and Cost of Frame Structures for Wooden and Concrete Apartment Buildings: Case Study from Finland

To date, the existing literature lacks any studies that compare timber and concrete apartment buildings in the Finnish context regarding their carbon footprint, handprint, and the cost of frame structures. This study rigorously analyzes and calculates the carbon footprint, carbon handprint, and costs associated with various structural solutions in a proposed multi-story building located in Laajasalo, Helsinki, Finland. While the primary focus is on wooden frame construction, exploring both its challenges and opportunities, this study also includes a comparative assessment with concrete frame construction. In Finland, regulations require a sprinkler fire extinguishing system to be installed inside. Also, weather protection is typically added to the top of building in connection with the construction of wooden apartment buildings. When the costs of a sprinkler system and weather protection are taken into account, the cost of achieving positive climate effects through a concrete frame is 290% higher than that of a solid wood frame. Our findings will provide a robust basis for assessing the sustainability and feasibility of construction methods, offering valuable insights into environmental and economic considerations for decision-makers in Finland and beyond as regulations evolve and awareness of climate impacts grows.

AED Inequity among Social Groups in Guangzhou

Automated external defibrillators (AEDs) are regarded as the most important public facility after fire extinguishers due to their importance to out-of-hospital cardiac arrest (OHCA) victims. Previous studies focused on the location optimization of the AED, with little attention to inequity among different social groups. To comprehensively investigate the spatial heterogeneity of the AED inequity, we first collected AED data from a WeChat applet. Then, we used the geographically weighted regression (GWR) model to quantify the inequity level and identify the socio-economic status group that faced the worst inequity in each neighborhood. Results showed that immigrants of all ages suffer a more severe AED inequity than residents after controlling population and road density. Immigrants face more severe inequity in downtown, while residents face more severe inequity in the peripheral and outer suburbs. AED inequity among youngsters tends to be concentrated in the center of each district, while inequity among the elderly tends to be distributed at the edge of each district. This study provides a new perspective for investigating the inequity in public facilities, puts forward scientific suggestions for future AED allocation planning, and emphasizes the importance of the equitable access to AED.

МОДЕРНИЗАЦИЯ СИСТЕМЫ ПОЖАРОТУШЕНИЯ В ТОВАРНО-РЕАГЕНТНОМ ХОЗЯЙСТВЕ

The advantages and disadvantages of fire extinguishing installations used in the commodity and reagent industry are considered

Study on Flowability Enhancement and Performance Testing of Ultrafine Dry Powder Fire Extinguishing Agents Based on Application Requirements

Flowability greatly affects the application of ultrafine dry powder fire extinguishing systems, while hydrophobicity and acute inhalation toxicity are concerns for fire extinguishing agents. In the present study, we examined the impact of hydrophobic fumed silica on the hydrophobicity and flow properties of ammonium dihydrogen phosphate as the base. Our findings revealed that incorporating 6 wt.% of hydrophobic fumed silica resulted in optimal flowability, accompanied by a hydrophobicity angle of 126.48°. The excessive inclusion of hydrophobic fumed silica impeded powder flow within the ammonium dihydrogen phosphate particles. Furthermore, the investigations indicated that the incorporation of a small quantity of bentonite (0.5 wt.%) amongst the three functional additives—bentonite, magnesium stearate, and perlite—offered further enhancements in powder flowability. In fire extinguishing experiments’ total flooding conditions (1 m3), the designed UDPA exhibited a minimum required extinguishing concentration of merely 41.5 g/m3, which is better than the publicly reported value. Moreover, observations on the well-being of mice subjected to nearly three times the extinguishing concentration at 60 s, 10 min, and 3 days, respectively, demonstrated the absence of acute inhalation toxicity associated with the designed UDPA. Collectively, the developed ultrafine dry powder fire extinguishing agent displayed promising performance and possesses broad applicability.

A REVIEW PAPER ON FIRE FIGHTING ROBOT

Firefighting robots are becoming increasingly important tools for combatting fires, particularly in hazardous environments. This paper reviews the latest advancements in real-time wireless firefighting robots. We explore the design considerations, functionalities, and sensor technologies employed in these robots. The paper highlights the importance of autonomous navigation, fire source detection and localization, and fire suppression mechanisms for effective firefighting. We discuss various fire extinguisher options beyond traditional water-based systems to address the limitations of water in extinguishing specific fires. Additionally, the paper examines the role of real-time communication for remote control and data transmission, enabling firefighters to make informed decisions and ensure their safety during operations. Finally, the review concludes by emphasizing the potential of real-time wireless firefighting robots to revolutionize fire response strategies and improve firefighter safety. · Key Words: Firefighting robots, localization, fire suppression mechanisms

Thermal runaway and soot production of lithium-ion batteries: Implications for safety and environmental concerns

Global energy shortages are becoming increasingly severe, and lithium-ion batteries are becoming an important substitute for fossil fuels. However, thermal runaway of a battery is a significant factor impacting battery industry development. Here, we conducted tests on battery thermal runaway using a combustion test chamber, analysing the effects of natural aging and state of charge (SOC) on battery thermal runaway. Additionally, EDS and XPS were used to analyse the soot particles formed during thermal runaway. Four stages in thermal runaway, e.g., battery bulge, smoke release, jet fire, and fire extinction. LiFePO4 with a higher SOC is more likely to cause thermal runaway. In addition, natural aging has an obvious impact on the intensity of thermal runaway. The gas products generated during a battery fire are identified as C1–C4 hydrocarbons. The soot generated by battery combustion presents a typical “core-shell” structure. The soot surface exhibits C–C, C–O, and O–H bonds, while the soot from early manufactured batteries also contains O–CO and π bonds. Soot contains not only C and O but also trace amounts of Li, F, P and Fe. These results reveal the characteristics of soot emission during thermal runaway of batteries, providing valuable insights for evaluating their toxicity and environmental impact.

Foreign Cooperation in the Japanese Government’s Fire Fighting Facilities Grant to Indonesia

Cooperation is part of associative social interaction. The existence of cooperation in a group is an important element, a constructive cooperation will create successful and good results in its implementation in groups. Like group, a country needs other countries to meet its needs. This then became the trigger for foreign cooperation. The mainly focus of this research is about the cooperation between the Governments of Indonesia and Japan in International Assistance in the form of Grants for Fire Extinguishing Facilities from the Japanese Government to three Regional Governments in Indonesia, namely: Garut, Belitung, and Paniai. The importanance about this research is to explain about implementation of the Cooperation between the Governments of Japan and Indonesia in the Grant of Fire Extinguishing Facilities to the Indonesian Government, especially the Belitung Regional Government. The study show that the implementation of cooperation between the government, in this case the Belitung Regional Government and the Japanese Fire Fighting Association, has a good and mutually beneficial effect, it's just that the implementation process has not optimal yet because there are several difficulties found such as time synchronization and the involvement of several ministries which causes disparities in Standard Operating. Procedure (SOP) in its implementation. This results in the possibility that the Belitung Government cannot realize this assistance this year, because the implementation has entered the end of the fiscal year which does not allow the arrival of goods or in this case objects of assistance where the last budget disbursement process was carried out in mid-December. Based on the data research on the Cooperation between the Japanese and Indonesian Governments in Fire Fighting Facilities Grants associated with the concept of good governance, the author's suggestion regarding this research is that hoped in the future the Indonesian government will further improve the quality of its bureaucracy by applying values to the concept of good governance so that problems and difficulties such as those encountered in the implementation of the Cooperation between the Japanese and Indonesian Governments in the Fire Fighting Equipment Grant can be minimized.

Investigation on a mobile fire extinguishing approach using liquid carbon dioxide as inert medium for underground mine.

Injecting carbon dioxide is the most effective means of preventing and extinguishing fires in sealing hazardous areas, but the traditional method slowly and remotely injects carbon dioxide gas into the well after gasification on the ground, which is dependent on the complete mine pipe network without cooling effect. To inject liquid directly from the tank with vacuum interlayer and heat insulating powder for rapid inerting and cooling, a new approach using track mobile platform to go deep into the underground mine disaster area is proposed, so the liquid can be delivered to the nozzle at the end of DN40 large diameter pipe, and the continuous gasification jet can be realized. The experimental results show that: (1) The liquid volume in a tank of vacuum degree within 2.0 Pa and 200 mm interlayer reduced no more than 15.5% after 48 days; (2) Taking the pressure in the tank as the power source, because of environmental differences inside and outside the pipe after 100 m pressure holding delivery, the physical form of liquid and gas could be converted instantly; (3) The continuous discharge time without ice blocking for a tank full of 2 m3 liquid was about 10.5 min under 25 L dual mode nitrogen pressurization, which is 1/12 of injection time after ground gasification; (4) Based on the temperature decrease trend measured at different positions, the cooling characteristics on liquid gasification jet path are quantified, and the calculation formula of temperature changing with time on the center line of liquid gasification jet is obtained. Through this new approach, the integration of vacuum insulated storage, safe mobile transportation, and continuous and rapid release with large flow can be achieved for the liquid carbon dioxide.

Development of an environmentally friendly gel foam and assessment of its thermal stability and fire suppression properties in liquid pool fires

Large-scale tank fires are one of the most challenging firefighting scenarios and pose significant threats to the safety of personnel and the integrity of equipment. The development of effective extinguishing agents is thus of both fundamental and practical importance in the controlling, mitigation, and suppression of tank fires. In this study, a novel environmentally friendly fire suppression foam based on gel-glycoside was developed using alpha-olefin sulfonate (AOS) and alkyl ethoxy polyglycosides (AEG) as the foaming agents, and sodium silicate, and sodium bicarbonate as the gelling and cross-linking agents respectively. The optimal ratios of the foaming agents were determined firstly by examining the foam expansion ratio and foam comprehensive value. Subsequently, the foamability, thermal stability, cross-linking time, and spreadability of the optimized formulations were analyzed. Finally, the fire extinguishing effects and performance in suppressing burnback of these formulations were examined and compared with those of a traditional film-forming fluoroprotein foam (FFFP). The experimental results indicated that the gel-glycoside foam, consisting of a composite foaming agent (AOS:AEG = 1:9), sodium silicate, and sodium bicarbonate at concentrations of 0.6, 2.4 and 3.7 wt%, respectively, exhibited the best spreadability and thermal stability. This formulation also showed excellent performance in cooling and suppressing burnback in the fire extinguishing tests, with a 90 % burnback time of 485 s, 45 % higher than that of FFFP. The present results clearly demonstrated that gel-glycoside foams can effectively control and suppress liquid pool fires and hence reduce the risk in potential re-ignition. These findings are also important for the further development of gel foams for extinguishing large-scale oil storage tank fires.

Development of an IoT-based firefighting drone for enhanced safety and efficiency in fire suppression

An uncontrolled fire poses severe threats to both humans and the environment, making firefighting a perilous and complex task. Traditional fire suppression methods are inefficient, costly, and without thorough testing, leading to delays in gaining control over fire outbreaks. This paper presents a novel firefighting drone aimed at mitigating risks to firefighters by extinguishing fires and providing real-time imaging, gas concentration and fire location data monitoring. The proposed intelligent quadcopter utilizes the Pixhawk PX4 microcontroller for precise control and the Pixhawk Telemetry system for data processing. The proposed device is constructed from an ultra-strength S500 Quadcopter frame, NodeMCU, Arduino Nano, various gas sensors, a servo motor to extinguish the fire and a camera to detect fire events in real time. Equipped with an FPV camera and a video transmitter, it transmits live video feed to the ground, enabling efficient navigation using the Flysky I6X controller. The intended position and height of the drone are controlled using an adaptive optimization technique known as fuzzy-based backstepping control. This article demonstrates the effectiveness of the device by collecting and analyzing gas emissions data from controlled burns of various materials. The drone successfully measured concentrations of CO, CO2, O3, SO2, and NO2 in affected areas, providing valuable insights for firefighting operations. Different levels of gases have been measured depending on the concentration from burning alcohol, clothes, plastic materials, paper, leaves, and so on. The novelty of this work lies in the development and comprehensive analysis of an IoT-based firefighting drone conducting extensive real-time experiments.

Study on suppression mechanism of NH4H2PO4 inhibiting gas flame of red pine pyrolysis

Ammonium phosphate fire extinguishing agents, due to their excellent cost-effectiveness and suitability for forest fires, have become one of the most commonly used fire suppressants for forest fire control. Among them, NH4H2PO4 fire extinguishing agent is the most widely applied. In this study, NH4H2PO4 (>90%) as the main component of dry powder fire extinguishers was selected as the suppressant to investigate the reaction mechanism of NH4H2PO4 interacting with red pine wood pyrolysis gas flames. Initially, we constructed a Bunsen burner experimental system suitable for NH4H2PO4/red pine wood pyrolysis gas/air. Although experimental methods yield the most intuitive empirical conclusions, measuring only the laminar flame speed of red pine wood pyrolysis gas/NH4H2PO4/air mixture does not adequately analyze the inhibitory mechanism of NH4H2PO4 on red pine wood pyrolysis gas flames. Additionally, due to limitations in experimental equipment and methods, it is not feasible to extend equivalence ratios and NNH4H2PO4 doses to large or small working conditions. Therefore, in this study, we utilized Chemkin software to construct theoretical models of flames under different conditions and performed calculations. We comprehensively analyzed the kinetic regulatory mechanisms of NH4H2PO4 interacting with red pine wood pyrolysis gas flames from aspects such as chemical inhibition, sensitivity of elementary reactions, elementary reaction yields, and chemical reaction pathways.

Effect of flame retardant hexafluorocyclotriphosphazene on combustion characteristics of electrolyte for lithium-ion batteries

Hexafluorocyclotriphosphazene (HFPN) is a promising flame retardant to be applied in lithium-ion batteries (LIBs) to decrease the fire risk during the treatment of electrolyte. In this manuscript, the influence of HFPN on the combustion characteristics of LIB electrolyte was investigated, the combustion behaviors and flame retardancy of the electrolyte with or without HFPN were systematically studied by using cone calorimeter, flash point meter and a series of standard equipment, as well as self-made water spray fire extinguishing platform. The flash points of 3 kinds of control group as base solution and 3 kinds of flame-retarded electrolyte were measured and obtained by SCKB3000 closed cup automatic flash point tester. The combustion characteristics of 6 types of electrolytes were analyzed by a cone calorimeter. The heat release rate (HRR), fire growth index (FGI), fire magnitude index (FMI) and other important combustion parameters of the electrolytes were studied. Based on the self-made water mist fire extinguishing platform, the fire extinguishing effect on 6 kinds of electrolytes under the same water mist condition was compared, and the influence of flame retardants in the fire extinguishing process was analyzed. The results showed that the change of flash point was obviously related to the composition of electrolyte. Flame retardant could reduce the peak HRR (pHRR) during electrolyte fire to a large extent, while it could also prolong the combustion duration of electrolyte pool fire. Under the action of fine water mist, the electrolyte pool fire would quickly extinguish, but there would remain a lot of smoke.

Preparation and fire extinguishing characteristics of inorganic solidified foam with large amount of slag

ABSTRACT Aiming at the problems of conventional cement-based foam plugging and filling materials, such as large amount of cement, low utilization rate of solid waste, unclear bonding, and plugging mechanism, it was proposed that a kind of plugging and preventing fire material named inorganic solidified foam was prepared from industrial slag, cement, and water-based foam as the main raw materials. Based on the fluidity, expansion ratio and mechanical strength of solidified foam, it was determined that S105 slag powder with high content of 60%~65% and the optimal content of the chemical activator 6%. The dry density of solidified foam was about 410~450 kg/m3, and the compressive strength reached 0.5~0.55 MPa. The formation process, the bonding-reinforcement mechanism, and the fire prevention characteristic fire of solidified foam were explored. The results showed that solidified foam could significantly improve the pozzolanic activity of solid waste under the effect of physical and chemical synergy, promoted the hydration reaction of the material, increased the structural compactness of the hydration product of the material, further improving the strength. Fire-fighting experiments and field application exhibited that solidified foam could rapidly diffuse and accumulate to high places through crack channels, quickly extinguish and cool down, and coat loose high-temperature coal piles, showing excellent effect of preventing coal spontaneous combustion. Moreover, the field test results showed that the solidified foam could quickly plug the air leakage, and reduce the CO concentration in the air leakage are. Specifically, the CO concentration of high falling area decreased from 315 ppm to 22 ppm in 3 days, eventually stabilizing below 10 ppm, thereby timely inhibiting the development of spontaneous combustion fire.

ASSESSMENT OF THE EFFICIENCY OF FIRE EXTINGUISHING SYSTEMS

As previously shown, many indicators characterise the quality of fire extinguishing systems. The most common quality indicator is fire extinguishing time. For fire extinguishing systems focused on extinguishing Class B fires using sprayed water, the authors have constructed a transcendental equation, the root of which is the fire extinguishing time. We derived the equation provided that the intensity of the sprayed water supply to the combustion centre to be described by the Heaviside function. The dynamic properties of fire are defined using the integral Laplace transform. We obtained the functional dependence of class B fire extinguishing time on fire parameters and showed that this time does not exceed a tenth of the constant fire time. In the first approximation, the inertial properties of the fire extinguishing system can be taken into account by the transfer function of an aperiodic link with a generalised time constant. For this case, we constructed a transcendental equation that determines the fire extinguishing time by the inertial fire extinguishing system. We note that, according to inertial properties, fire extinguishing systems fall into three classes. For each of the three classes, estimates of the extinguishing time of a class B fire were obtained, depending on the dynamic properties of this fire. The results show that this time can change several times. The authors have introduced the criterion for the efficiency of fire extinguishing systems, which characterises the degree of approximation of the speed of the fire extinguishing system to the maximum possible value. This criterion also indicates how much it is necessary to increase the extinguishing agent mass supplied per unit area of the fire relative to the extinguishing agent mass supplied in leaps per unit area of the fire, provided that the extinguishing times are the same. We obtained estimates of the effectiveness of fire extinguishing systems using this criterion. Furthermore, we provided recommendations on the use of the efficiency criterion. Keywords: fire extinguishing system, extinguishing time, efficiency criterion.