Mechanisms Of Fire Extinguishment Research Articles

분전반, 배전반 등에 사용하는 질산칼륨 기반의 소공간 소화장치의 성능에 관한 기초 연구 - 소화메커니즘 및 A급 소화성능을 중심으로

As there was no objective date on the fire extinguishing mechanism and performance of potassium nitrate-based small space fire extinguisher that can automatically extinguish fires in small spaces (less than 0.36 ㎡) such as distribution boards and distribution boards, we attemped to conduct basic research on this. We sought to confirm the importance of fires in switchboards and other devices through fire statistical analysis of electrical factors, and analyzed fire extinguishing mechanisms that react with heat based on potassium nitrate. We also sought to determine the interconnectivity of related variables through Class A fire extinguishing tests. Through analysis of fire statistics, the importance of electrical fires was confirmed and the cause of fire in the switchboard was investigated. By investigating its composition, it was found that it was a safe material that could be used for fire extinguishing, and that in the event of a fire, the thermal decomposition of KNO3 produced condensed aerosol particles, K2CO3, which could extinguish the fire. Through the Class A fire extinguishing test of the switchboard, it was confirmed that the fire could be reliably extinguished. The following conclusions were drawn through this study. 1. Analysis of fire statistics confirmed that electrical factors were the biggest cause of fire and that fires caused among this short circuit and insulation deterioration were the main causes. 2. The fire risk of switchboards, distribution boards, etc. was confirmed, and it was found that it was necessary to install simple fire extinguishers for small spaces that can quickly respond to and extinguish fires. 3. The fire extinguishing mechanism of potassium nitrate was confirmed to extinguish the fire by generating condensed aerosol particles, K2CO3, through thermal decomposition of KNO3 when a fire occurs. 4. Through the Class A fire extinguishing performance test, it was confirmed that there was a relationship between fire extinguishing delay time, weight, and volume, and the relationship could be expressed as , and it was found that a value of 1 or more is required for fire extinguishing.

Modification and Application Performance Study of Ultra-Fine Dry Powder Extinguishing Agent.

Ultra-fine dry powder extinguishing agent (UDPEA) is a promising alternative to Halon agents in aviation firefighting. The formulation of UDPEAs should balance environmental friendliness and practical engineering requirements, including high extinguishing efficiency, excellent flowability, and prolonged anti-reignition. This study investigates the effects of three modification methods (single perfluorooctyl triethoxysilane (FOTS), single N-(3-Triethoxysilylpropyl)perfluoro(2,5-dimethyl-3,6-dioxanonanoyl)amide (PFPE), and a combination of FOTS and PFPE at various mass ratios (2.0:0.4, 1.6:0.8, 1.2:1.2, 0.8:1.6, 0.4:2.0) (g)) on the performance of sodium bicarbonate-based UDPEA. The results indicate that using FOTS or PFPE alone improves the water and oil contact angles, but still fails to meet the required hydrophobicity and oleophobicity standards, and it also reduces the flowability and fire-extinguishing capability. A combination of FOTS and PFPE at the 1:2 ratio yields the best performance, with the water and oil contact angles of 145.169° and 143.542°, respectively, the lowest flowability index (0.224), minimal extinguishing concentration and time (14.183 g/m3 and 1.976 s, respectively), which is only 52.7% and 68.3% of those of the unmodified UDPEA's (26.927 g/m3 and 2.893 s), and the longest anti-reignition time (68.5 s). In addition, the fire-extinguishing mechanisms (chemical inhibition and physical heat absorption) and anti-reignition mechanisms of the modified UDPEA (with the FOTS to PFPE ratio of 1:2) were revealed. This research aims to design an eco-friendly, high-performance UDPEA as an effective substitute for Halon extinguishing agents. These findings can provide valuable insights for evaluating and selecting aviation fire-extinguishing agents.

Environmentally friendly fluorine-free fire extinguishing agent based on the synergistic effect of silicone, hydrocarbon surfactants and foam stabilizers

The environmentally friendly fluorine-free fire extinguishing agent based on the silicone surfactant was developed in order to solve the environmental hazards and bio-accumulative of traditional aqueous film-forming foam (AFFF). The carboxyl modified polyether polysiloxane surfactant (CMPS) was an efficient alternative to fluorocarbon surfactant, which was firstly synthesized via the esterification reaction using hydroxyl-containing polyether modified polysiloxane (HPMS) and maleic anhydride (MA) as raw materials. Then the surface activity, foam properties, micellar morphology of the CMPS and four hydrocarbon surfactants, as well as their mixture are evaluated by surface tension, Ross-Miles and cryo-transmission electron microscopy (Cryo-TEM). And the suitable key amount of CMPS and hydrocarbon surfactants added to the extinguishing agent were optimized by orthogonal tests. Moreover, the effect of foam stabilizer on the surface activity, foam property and fire extinguishing performance of fire extinguishing agent are also analyzed. Consequently, a new environmentally friendly fluorine-free fire extinguishing agent was prepared and the surface tension, the interfacial tension, foam properties, bubble morphology, spreading behavior and fire extinguishing mechanism were systematically characterized. The Cryo-TEM results illustrate that the intense interaction among silicone and hydrocarbon molecules exists in the the mixture of CMPS and hydrocarbon surfactants, which is produced through the change of micellar morphology, i.e. microscopic larger spheroidal micelles of CMPS transited to smaller spheroidal micelles and wormlike micelles in the mixed system. The surface tension of synthesized foam extinguishing agent is 22.3 mN/m and the spread coefficient is 0.9 mN/m, which has excellent surface activity and spreading property. The prepared foam extinguishing agent exhibits superior fire-fighting property, which can be attributed to the high surface activity, good foam property and superior foam stability. The research results of this paper lay a theoretical foundation for the research and development of efficient environmentally friendly foam extinguishing agent.

Catalytic polymer self-cleavage for CO2 generation before combustion empowers materials with fire safety

Polymeric materials, rich in carbon, hydrogen, and oxygen elements, present substantial fire hazards to both human life and property due to their intrinsic flammability. Overcoming this challenge in the absence of any flame-retardant elements is a daunting task. Herein, we introduce an innovative strategy employing catalytic polymer auto-pyrolysis before combustion to proactively release CO2, akin to possessing responsive CO2 fire extinguishing mechanisms. We demonstrate that potassium salts with strong nucleophilicity (such as potassium formate/malate) can transform conventional polyurethane foam into materials with fire safety through rearrangement. This transformation results in the rapid generation of a substantial volume of CO2, occurring before the onset of intense decomposition, effectively extinguishing fires. The inclusion of just 1.05 wt% potassium formate can significantly raise the limiting oxygen index of polyurethane foam to 26.5%, increase the time to ignition by 927%, and tremendously reduce smoke toxicity by 95%. The successful application of various potassium salts, combined with a comprehensive examination of the underlying mechanisms, underscores the viability of this strategy. This pioneering catalytic approach paves the way for the efficient and eco-friendly development of polymeric materials with fire safety.

Preparation of a novel environmental-friendly lithium-ion battery fire suppression microcapsule and its fire extinguishing mechanism in coordination with ABC dry powder

Lithium-ion battery fires are one of the main bottlenecks hindering the industrialization development of lithium-ion batteries. The existing fire extinguishing materials can not completely solve the problems of lithium-ion battery cooling, reignition, pollution and so on. Therefore, it is imperative to develop efficient and environmentally friendly fire extinguishing materials. In this paper, environmentally friendly CTS-SA@F7A-Novec 1230 microcapsule fire extinguishing agent with good flame retardant properties was prepared by coating heptafluorocyclopentane (F7A) and perfluorohexanone (Novec 1230) fire-extinguishing materials by the complex coalescence method using chitosan (CTS) and sodium alginate (SA) as the shell material, and the fire-extinguishing effects of the three methods, namely, N2+ABC dry powder + microcapsule (NAM), N2+ABC dry powder (NA), and N2(N), were comparatively analyzed. The research results indicate that, CTS-SA@F7A-Novec 1230 microcapsules were well formed and had excellent thermal stability; The peak heat release rate (PHRR) of CTS-SA@F7A-Novec 1230 microcapsules decreased by 22.56 w/g after the addition of CTS-SA@F7A-Novec 1230 microcapsules to the composite battery materials, and the temperature TPHRR corresponding to PHRR increased by 18.09 °C accordingly, which resulted in a good flame retardant property of the materials; The cell cooling effect was ranked as NAM > NA > N, and the maximum cell surface temperatures under these three methods were reduced by 10.34%, 17.30% and 18.68%, respectively, compared with the thermal runaway experimental data; The fire extinguishing effectiveness was ranked as NAM > NA > N. The maximum flame temperature was reduced by 52.10%, 40.53%, and 23.95%, and the flame extinguishing time was shortened by 71.02%, 64.12%, and 22.48%, respectively, with these three methods compared to the thermal runaway flame data. Based on this, the three-phase synergistic extinguishing mechanism of gas, liquid and solid under the NAM method is revealed, which provides an important reference for the design of extinguishing agents and extinguishing methods for lithium-ion batteries.

Thermal characteristics of fire extinguishing agents in compartment fire suppression.

Water and foam have different fire-extinguishing mechanisms. Traditional foam and compressed air foam (CAF) have different bubble structures. These differences result in different thermal characteristics, which affect the extinguishing abilities during a fire. In this study, the differences in the thermal characteristics of three different extinguishing agents (water, traditional foam, and CAF) were investigated by suppressing a compartment fire. With an ignition source in the compartment (6 m × 3 m × 3 m), the agent was preferentially applied to the outside wall of the compartment. The effects of internal cooling and burnback resistance generated from the outer wall were evaluated. The performance of each agent in shielding firefighters from radiant heat while suppressing the fire inside the compartment was evaluated. When the outside wall of the compartment was covered with each of the agents, all agents were found to reduce the room temperature. When CAF was applied, the delay time until temperature re-rise was approximately 1.76-4.5 times longer than that when water was used. In addition, foaming agents exhibited a higher heat-shielding effect than water during the initial suppression. Thus, considering the thermal characteristics of these agents, fire suppression can be more effective if foam agents are used.

Advancement of microcontroller-based fire suppression system for enhanced safety in sugar cane plantations

The occurrence of accidental fires in sugarcane plantations is a significant cause of pre-harvest loss in the sugar industry, particularly during arid seasons. This paper introduces the conceptualization and implementation of a microcontroller-based prototype system for mitigating accidental fires in sugar cane plantations. The proposed system encompasses two distinct subsystems: the field monitoring and the fire control unit. The Field monitoring system, deployed within the sugarcane field, assumes responsibility for fire detection via smoke detectors, infrared detectors, as well as carbon dioxide and carbon monoxide detectors, which are accompanied by a fire extinguishing mechanism. Conversely, the fire control unit, installed at the fire brigade office, establishes wireless communication with the field monitoring system through the global system for mobile communication (GSM) network. Upon detecting a fire, the microcontroller promptly dispatches a fire alert to the fire brigade while simultaneously activating water pumps to suppress the fire until the brigade arrives to fully extinguish it. Furthermore, the fire control unit triggers the fire alarm and exhibits the global positioning system (GPS) coordinates of the burning field to facilitate precise localization. The proposed system uses the Arduino-Mega and Arduino- Leonardo microcontroller platforms and is programmed using the C++ programming language in Visual-Studio-Code software and the Arduino integrated development environment. Designed prototype can detect fires and alert the fire brigade in less than twenty seconds and activate water pumps in less than one second after fire detection.

Experimental study on the effectiveness of dry water material to suppress oil pool fire and analysis of fire extinguishing mechanism

Experimental study on the effectiveness of dry water material to suppress oil pool fire and analysis of fire extinguishing mechanism

Analysis of Flow Field Characteristics of the Propane Jet Combustion Flame

In order to effectively prevent fire accidents and improve fire management capability, this paper describes the independent designs and builds of an experimental low-cost particle image velocimetry platform for a propane jet combustion flame using traditional mutual correlation theory. The particle image velocimetry (PIV) algorithm is written based on MATLAB software, allowing it to realise image preprocessing, multi-level grid window deformation inter-correlation calculations, and other functions. Fluid flow velocity and vorticity are used as entry points to study the flame combustion mechanism. The air flow field and vorticity above the propane jet flame are analysed. The results show that, from the level of fluid flow velocity, the maximum fluid flow velocity in the test area does not exceed 0.23 m/s, and the maximum transverse fluid flow velocity is close to 0.15 m/s. Additionally, the longitudinal fluid flow velocity is opposite the upper and lower portions of the longitudinal flow velocity, and there is a swirling phenomenon in the propane flame jet. From the vorticity level, the closer to the centre of the jet in the vortex plane, the faster the air flow speed, and simultaneously, in the upper and lower parts of the vortex, the air flow travels in the opposite direction and is of equal size. The particle image velocimetry platform that was independently designed in this study can efficiently characterise the dynamic flow field and the flow characteristics of complex combustion chambers, simultaneously ensuring high efficiency and reducing research costs. It provides a measurement method and experimental basis for the development of fire extinguishing equipment and numerical simulation, while also helping us to carry out a series of subsequent studies on fire extinguishing mechanisms.

The preparation and fire extinguishing mechanism research of a novel high-efficiency KHCO3 @HM dry powder

Hydromagnesite (HM) is a widely distributed primary natural carbonate mineral. To expand the application range of hydromagnesite and tap its fire-extinguishing potential, a new type of high-efficiency KHCO3 @HM dry powder was prepared by coating potassium bicarbonate on the surface of hydromagnesite with a dip coating method. KHCO3 @HM dry powder obtained a chemical inhibition effect through this method, and the fire extinguishing efficiency has been further improved. A series of tests were carried out to confirm the excellent physical and chemical inhibition effect of KHCO3 @HM dry powder. Specific surface area tests showed that the specific surface area of KHCO3 @HM dry powder (31.405 m2/g) was higher than NH4H2PO4 dry powder (12.766 m2/g). Flowability tests showed that KHCO3 @HM dry powder (0.04 g/s) achieved the same flowability as NH4H2PO4 dry powder (0.04 g/s). Local oil basin fire experiments showed that the average fire extinguishing time of KHCO3 @HM dry powder was shorter with less powder consumption. Under 0.2 MPa driving pressure, the fire extinguishing time of KHCO3 @HM dry powder was 2.2 s faster than NH4H2PO4 dry powder, and the dry powder consumption was 3.71 g less than NH4H2PO4 dry powder. The cooling effect of KHCO3 @HM dry powder (208 ℃) in 10 s was better than NH4H2PO4 dry powder (157 ℃), and KHCO3 @HM dry powder (399 ppm) showed a better smoke suppression effect than NH4H2PO4 dry powder (545 ppm). The pyrolysis of KHCO3 @HM dry powder reduced the fire temperature, diluted the oxygen concentration, and captured free radicals. The final pyrolysis products formed a thick oxide film to provide good heat insulation and asphyxiation effects. The excellent cooling, dilution, asphyxiation, and chemical inhibition mechanisms of KHCO3 @HM dry powder were demonstrated, and finally achieved a comprehensive performance comparable to NH4H2PO4 dry powder.

Study on fire extinguishing mechanism of allophanate based on Monnex dry powder

Monnex (allophanate) dry powder has a good fire extinguishing effect and is environmentally friendly. However, the reaction processes of allophanate with OH· and H· free radicals, which are of great importance for investigating its fire suppression mechanisms, are still unclear. In this work five reaction pathways related to the pyrolysis of ureyl formates, five pathways to capture OH· radicals and seven pathways to capture H· radicals were studied. It was found that, for the CO2 and NHCONH2 generation pathway possesses the energy barrier much lower than others in pyrolysis of allophanate. The generation of NHCONHCOO + H2O is the most feasible reaction channel for the reaction of allophanate with OH free radical. Moreover allophanate and its derivatives capture H radicals to achieve continuous consumption of free radicals. This study shows, it is worth further studying its applicability in fire extinguishing applications.

Rancang Bangun Robot Beroda Penggerak Kipas dengan Deteksi Api Berbasis Mikrokontroler Atmega328

Electricity is inseparable from human daily life. Many devices operate by utilizing electrical energy. If there is negligence in its usage, it can cause electrical short circuits and even lead to fires. Fires that occur can have a significant impact on the surrounding community and the environment. To address this issue, a prototype in the form of a robot needs to be developed, which has the ability to detect and extinguish fires. Utilizing technological advancements such as fire detection sensors that can communicate with a microcontroller to search for and detect the presence of fire, as well as assistance from ultrasonic sensors to detect obstacles. The fire extinguishing mechanism of this robot prototype utilizes a fan module that becomes active when a fire is detected.

Alkaline potassium aluminum carbonate: A novel high-efficiency dry powder extinguishing agent with high heat-resistant

Alkaline potassium aluminum carbonate (KAl(OH)2CO3) has potential application as an active medium for dry powder fire extinguishing due to its special molecular structure. In this paper, the application of KAl(OH)2CO3 as a high-temperature resistant dry powder extinguishing agent is first discussed. Firstly, the pyrolysis kinetics of KAl(OH)2CO3 was explored using thermal analysis techniques, including model-free and model-fitting methods. The pyrolysis of KAl(OH)2CO3 can be divided into three stages, with E values of 357.7 and 244.8 kJ/mol for stage 1 and stage 3, respectively. Higher activation energy of KAl(OH)2CO3 (T5 wt%=550 K, Tmax=648 K) means that it will not be deactivated prematurely in the high-temperature region. Moreover, the fire-extinguishing performance of KAl(OH)2CO3 is much better than that of BC dry powder fire extinguishing agent, which can suppress n-heptane and aviation kerosene pool fires within 6.00 s and 7.21 s. The possible fire-extinguishing mechanism of KAl(OH)2CO3 is also proposed. Therefore, KAl(OH)2CO3 is expected to be a high-temperature resistant dry powder extinguishing agent, which solves the application of existing dry powder fire extinguishing agents in high-temperature areas such as aircraft engine compartments.

Toward better Halon substitutes: Effects of H content on pyrolytic and fire-suppressing mechanisms of ozone-friendly fluorinated alkanes

Halon extinguishants have been prohibited due to the caused damages to the stratospheric ozone layer. For Halon replacement, ozone-friendly fluorinated alkanes are used as transitional Halon substitutes. In order to unravel the relationship between chemical structures and fire-extinguishing performance of fluoroalkane agents, we investigated the effects of hydrogen content on pyrolytic and fire-extinguishing mechanisms of fluoroalkanes including HFC-236fa (CF3CH2CF3), HFC-227ea (CF3CHFCF3) and PFC-218 (CF3CF2CF3), which may provide some guidance on efficient exploration of new substitutes for Halon extinguishant. Both the experimental and theoretical methods were employed in this study. It was found that the energy barrier of CF3· fire extinguishing free radical generated by the three fluorinated alkanes increases slightly with the increase of H content. The reduction of hydrogen content notably promotes the thermal stability of fluorinated alkanes and the productivity of incombustible pyrolytic products. The HFC-236fa agent exhibits remarkable cooling effect upon the combustion cycle via endothermic pyrolysis, while the PFC-218 agent extinguishes flame predominantly through the dilution effect on the flammable gas. Remarkably, a lower hydrogen content effectively inhibits the production of flammable alkenes, corrosive and toxic pyrolytic products. Although PFC-218 agent exhibits the highest fire-extinguishing concentration (FEC) relative to the other two counterparts, the PFC-218 manifests the subtlest combustion promotion and releases the least corrosive products, which inhibits the suddenly risen temperature in the combustion region and reduces corrosive and poisonous products. These findings provide new understanding and guidance on the molecular designing and screening of environmental-friendly and efficient Halon substitutes.

Study on the Preparation of Montmorillonite-Type Multiple Network Composite Gel for Coal Spontaneous Combustion and Its Firefighting Mechanism.

This paper proposes a new montmorillonite-type multiple network composite gel for the prevention of coal spontaneous combustion. The first network is formed by the cross-linking of polyvinyl alcohol (PVA) and boric acid under alkaline conditions. The second network is formed as a result of intermolecular hydrogen-bonding interactions between polyacrylamide (PAM) and polyvinyl alcohol. Montmorillonite (MMT) is designed as the backbone material in the preparation of composite gels. The optimal ratios of the reactants of the composite gel were determined through orthogonal experiments. The experimental results showed that PVA had the greatest influence on the gelation time, whereas the PAM concentration had the strongest influence on the gel permeability. The optimal blending ratio was 4% MMT + 2.5% PVA + 1.5% PAM. The chemical performances of the composite colloids, such as inhibition rate, reactive functional groups, and kinetics, were investigated. Results showed that multiple network composite gels could effectively inhibit the coal spontaneous combustion reaction. Based on the principle of coal spontaneous combustion and the cross-linking network structure of the composite gel, the flame-retardant and fire-extinguishing mechanisms were also explored in terms of both physical and chemical inhibition pathways.

Preparation and fire extinguishing mechanism of core-shell solid-liquid composite powder containing ammonium dihydrogen phosphate

A solid-liquid composite powder containing core-shell structure is created under the guidance of theoretical level. Among them, the factors affecting preparation are attributed to stirring speed, solid-liquid mass ratio, stirring time and additive concentration. The results of reduced-size fire chamber indicate that the core-shell structured powder containing NH4H2PO4 (WS-2) can suppress diesel flame more effectively than commercial dry powder (CDP) and common core-shell structured powder (WS-1). Besides, WS-2 shows the highest degree of temperature drop, which is 21.14% and 39.82% higher than CDP and WS-1, respectively. Combined with the results of Thermogravimetric analyzer (TGA) and Fourier transform infrared absorption spectroscopy (FTIR), it can be inferred that WS-2 fully embodies multiple inhibitory effects such as isolation, cooling, asphyxiation and chemical suppression. Ultimately, the excellent fire extinguishing performance brought by its unique structure is demonstrated. This study is of great significance for the determination of technological parameters and application of core-shell powders.

Preparation and fire extinguishing mechanism of novel fire extinguishing powder based on recyclable struvite

Preparation and fire extinguishing mechanism of novel fire extinguishing powder based on recyclable struvite

Automated Fire Extinguishing System Using a Deep Learning Based Framework

Fire accidents occur in every part of the world and cause a large number of casualties because of the risks involved in manually extinguishing the fire. In most cases, humans cannot detect and extinguish fire manually. Fire extinguishing robots with sophisticated functionalities are being rapidly developed nowadays, and most of these systems use fire sensors and detectors. However, they lack mechanisms for the early detection of fire, in case of casualties. To detect and prevent such fire accidents in its early stages, a deep learning-based automatic fire extinguishing mechanism was introduced in this work. Fire detection and human presence in fire locations were carried out using convolution neural networks (CNNs), configured to operate on the chosen fire dataset. For fire detection, a custom learning network was formed by tweaking the layer parameters of CNN for detecting fires with better accuracy. For human detection, Alex-net architecture was employed to detect the presence of humans in the fire accident zone. We experimented and analyzed the proposed model using various optimizers, activation functions, and learning rates, based on the accuracy and loss metrics generated for the chosen fire dataset. The best combination of neural network parameters was evaluated from the model configured with an Adam optimizer and softmax activation, driven with a learning rate of 0.001, providing better accuracy for the learning model. Finally, the experiments were tested using a mobile robotic system by configuring them in automatic and wireless control modes. In automatic mode, the robot was made to patrol around and monitor for fire casualties and fire accidents. It automatically extinguished the fire using the learned features triggered through the developed model.

Study on fire extinguishing performance of different foam extinguishing agents in diesel pool fire

The physical properties and fire extinguishing performance in diesel fire of aqueous film-forming foam (AFFF) and protein foam (PF) were studied, and the fire extinguishing mechanism of different foams were also analyzed. The results show that 6%AFFF and 6%PF have better performance than that of 3%AFFF and 3%PF, respectively, and AFFF possess higher expansion ratio, 25% drainage time and surface tension than PF at the same concentration. The fire extinguishing test show that the extinguishing performance of foam enhanced with the increase of gas-liquid ratio firstly, and decreased subsequently. The best fire extinguishing performance were achieved when gas-liquid ratio of 6%AFFF and 6%PF were 17 and 20, and the extinguishing agent dosage were 229 ml and 260 ml, respectively. Compared with PF, the fire extinguishing time and agent dosage of AFFF are reduced by 10% and 6.15% respectively at gas-liquid ratio of 20. Besides, AFFF can form more dense, stable and high-multiple foam cover layer, endow it with better fire extinguishing performance than PF. However, PF can reduce the temperature around the oil pool more quickly, showing better cooling effect than AFFF.

An Experimental Investigation of the Influence of Flow and Pipe Diameter on the Fire Extinguishing Efficiency of Nitrogen Injection in a Narrow Confined Underground Space

In this study, an underground pipe gallery was taken as the research subject to explore the influence of nitrogen injection flow rate and pipe diameter on the fire extinguishing efficiency in an underground narrow confined space. A liquid nitrogen fire extinguishing test system for the underground narrow confined space was built. The fire extinguishing time, flame height, temperature, and oxygen concentration under different conditions were recorded by liquid nitrogen fire extinguishing tests, and the variations in the characteristics of these data were analyzed. Furthermore, the fire suppression factor, cooling factor, and asphyxiation factor were introduced to quantify the influence of the nitrogen flow rate and pipe diameter on extinguishing efficiency. According to the results, the fire was effectively extinguished by liquid nitrogen in the underground confined space through asphyxiation as the main fire extinguishing mechanism, and the extinguishing time was about 95.5% less than that in the self-extinguishing test. Although the fire suppression efficiency is positively related to the nitrogen injection flow, the asphyxiation efficiency can be reduced when the flow rate is excessive or too weak. Additionally, the asphyxiation factor and fire suppression factor are highly sensitive to the injection pipe diameter. Therefore, a valuable reference is provided in this study for promoting the future engineering application of liquid nitrogen fire extinguishment.