A new tunnel fire detection and suppression system based on camera image processing and water mist jet fans

This study aims to experimentally investigate the combustion products of fires suppressed/extinguished by two water-based fire suppression systems, namely, sprinklers and water mist systems. A total of thirteen experiments were conducted with various suppression system configurations, i.e., with a sprinkler, a low-pressure (LP) water mist, and a high-pressure (HP) water mist, at operating pressures ranging from 2 to 60 bar and water flow rate ranging from 10 to 206 L/min. Each experiment was conducted twice, except for the baseline experiment with no suppression. The fuel was a high-density polyethylene (HDPE) pallet placed on two wood pallets. During all the stages of fire development, suppression with water, and post-suppression, the combustion products were sampled through Fourier-Transform Infrared Spectroscopy (FTIR) using a gas analyzer capable of operating in high humidity. The main combustion products identified were CO2, CO, and H2O. In addition, NOx (nitrogen oxides), CxHy (light-weight hydrocarbons), and HCN were present in relatively high concentrations. All the tested fire suppression systems were effective in reducing the fire size and cooling down the gases. However, when the fire could not be immediately extinguished, the NOx, CxHy, and HCN concentrations were higher than those in the baseline experiment. Moreover, it is observed that the HP water mist system was more effective than the sprinkler and low-pressure water mist systems in reducing the amount of combustion gases during suppression, resulting in lower Fractional Effective Doses (FED). It was observed that the combustion products returned to ambient conditions after five minutes of deactivation. The results from this study provide much-needed validation data for the effectiveness of water-based suppression systems, not only in reducing the fire size but also in reducing the production of acute toxic gases, which is important for considerations regarding evacuation, firefighting, and post-extinguishment conditions.

The present work is an attempt to offer a comprehensive review of literature contributions, phenomenology and relevant results on water-mist systems. In particular, the water mist characterization and behavior in the field of fire con- trol and suppression have been identified as the main areas of investigation. Some key parameters have been analyzed to gain a quantitative evaluation of the physical phenomena related to water-mist systems. The water-mist fire suppression systems are an excellent alternative to halon fire protection systems, and they are now be- ing used in many areas, including marine and industrial applications. Therefore, a wide survey of the complete number of literature works on this topic would exceed the full length of the present paper and only some examples of important con- tributions will be mentioned here. This paper proposes an introductory list of relevant literature works and this reference survey is then deepened with work and result details on suppression mechanisms, spray characterizations and experimen- tal and numerical approaches. The final summary stresses out that a lot of experimental and numerical research and much application experience are still needed to gain better knowledge on water-mist systems, even if they already seem to be very promising in terms of efficiency and potentialities in fire control and suppression.

PurposeThe water mist fire suppression system (WMFSS) is an environmentally friendly fire protection system, replacing the total flooding halon system. It is starting to be popular in Hong Kong with five systems approved. However, such systems were tested under some scenarios very different from real fires. Performance under practical scenarios should be evaluated thoroughly. Full‐scale burning tests should be carried out to support that the systems would work in real fire scenarios as expected. This paper aims to briefly discuss whether the water mist system is suitable for use in Hong Kong.Design/methodology/approachFive water mist systems were approved in Hong Kong based on the fire test certificate provided by the manufacturers. Four systems were selected in this paper for discussion. Conditions of the fire scenarios in which the approved systems would work are described. The test scenario encountered should match with real fires. Such systems would work satisfactorily in the application area proposed. They are good for enclosed rooms such as machinery spaces and plant rooms. But applying such systems for use in retail areas or libraries should be watched carefully, particularly those with high ventilation rates.FindingsIt is observed that the four approved systems were only evaluated on machinery plant rooms with volume less than 500 m3. They are demonstrated to be effective in extinguishing a wide range of bigger Class B fires with very little residual water in a short time. However, the loss of water vapor under mechanical ventilation conditions might reduce the extinguishing capability of mist. The water mist nozzle should not be installed near to the exhaust and supply positions of the mechanical ventilation system. Note that WMFSS is not effective in handling shielded fires due to the lower mist concentration.Practical implicationsFull‐scale burning tests on pool fires of different shapes under water mist were carried out. It was demonstrated that WMFSS might not work under some fire scenarios. Different scenarios on the amount and arrangement of combustibles, room geometry and sizes would affect the system performance. Further, shop fires were burnt with performance of the water mist system evaluated. Heat release rate curves on the shop fire with and without discharging water mist are measured. Reignition occurred once water supply was shut down, burning up all combustibles.Originality/valueEffectiveness of WMFSS is determined by other factors, including the spray characteristics, fire size, ceiling height and ventilation rate in the compartment. Their performance in mechanical ventilation rooms should be watched. As a result, the total flooding system might not be so good. Localized water mist systems directed to the hazard might be more reliable to suppress fire. Water nozzle design is a key area as raised by the principal author. Anyway, the possible fire scenarios must be identified in designing workable WMFSS. Full‐scale burning tests should be conducted to demonstrate the system performance.

Tunnel fires pose severe risks due to confined geometry, limited evacuation options, and rapid smoke propagation. This literature review compiles insights from recent studies on smoke movement, ventilation control, fire suppression, and evacuation behaviour in tunnel environments. It also highlights the growing use of simulation tools like PyroSim and Pathfinder to analyse fire dynamics and human response. Key findings across studies include the significance of critical ventilation velocity, the risks of smoke back- layering, and the throttling effect in high-heat-release fires. While systems like water mist and deluge sprinklers improve tenability, their effectiveness depends on placement, droplet behaviour, and airflow interaction. Evacuation outcomes are shown to rely heavily on visibility, exit spacing, and guidance systems. The review underscores that tunnel safety requires a coordinated approach, where fire suppression, ventilation, and evacuation systems work in synergy. This paper aims to provide a more consolidated foundation for designing a more resilient tunnel fire safety system by thoroughly examining the tested strategies and simulation based evaluations. Keywords: Tunnel Fire, Fire Dynamics, Ventilation, Fire Suppression, Evacuation, PyroSim

Firefighting systems for electrical cables are crucial for safety and functionality during emergencies. They ensure the continuity of critical safety systems, minimize fire spread, and reduce the risk of smoke and toxic gas exposure. Therefore, the objective of the current work is to experimentally investigate the performance and effectiveness of a water mist firefighting system for protecting electrical cables, contributing to the design and development of water mist nozzles. Three types of cables, namely navigation cable, power cable, and electrical cable, were used to investigate the fire protection performance of two different fire nozzles: the Viking nozzle and the ES nozzle. The experiments were conducted in the Firefighting Laboratory of the Mechanical Power Department, Faculty of Engineering (El-Mataria), Helwan University, using a low-pressure water mist system to extinguish cable fires. The experimental comparison between the water mist nozzles was based on visual observation, temperature, fire extinction time, working pressure and water flow rate. The results of this experiment showed that low pressure water mist system is very effective for small-scale cable fires. Moreover, the Viking nozzle achieved superior performance by reducing the fire suppression period by around 76%, 55% and 25% for power cables, electrical cables, and navigation cables, respectively, and shortening the cooling period by about 82 - 83% compared with the ES nozzle.

2NASA Glenn Research Center, Cleveland, Ohio 44135 During the Constellation Program, the development of spacecraft fire safety technologies were focused on the immediate questions related to the atmosphere of the habitable volume and implementation of fire detection, suppression, and postfire clean-up systems into the vehicle architectures. One of the difficulties encountered during the trade studies for these systems was the frequent lack of data regarding the performance of a technology, such as a water mist fire suppression system or an optically-based combustion product monitor. Even though a spacecraft fire safety technology development project was being funded, there was insufficient time and funding to address all the issues as they were identified. At the conclusion of the Constellation Program, these knowledge gaps formed the basis for a project proposed to the Advanced Exploration Systems (AES) Program. This project, subsequently funded by the AES Program and in operation since October 2011, has as its cornerstone the development of an experiment to be conducted on an ISS resupply vehicle, such as the European Space Agency (ESA) Automated Transfer Vehicle (ATV) or Orbital Science’s Cygnus vehicle after it leaves the ISS and before it enters the atmosphere. The technology development efforts being conducted in this project include continued quantification of low- and partial-gravity maximum oxygen concentrations of spacecraft-relevant materials, development and verification of sensors for fire detection and post-fire monitoring, development of standards for sizing and selecting spacecraft fire suppression systems, and demonstration of post-fire cleanup strategies. The major technology development efforts are identified in this paper but its primary purpose is to describe the spacecraft fire safety demonstration being planned for the reentry vehicle.

Electricity is an important energy supply for industry, and long‐distance transmission in China mainly relies on cable tunnels, while cable tunnel fires occur frequently. A 1:1 scale tunnel model with a length of 20 m, a width of 2.5 m, and a height of 2.5 m was used to conduct experimental research on the temperature field of the ceiling of a high‐voltage fine water mist suppression cable tunnel. The article conducted experimental research on parameters, such as nozzle pressure, nozzle position, and longitudinal ventilation speed in high‐pressure water mist systems using n‐hexane as the ignition source. The results indicate that the high‐pressure water mist system can effectively reduce the ceiling temperature during cable tunnel fires. When the mechanical smoke evacuation system is activated, it leads to a reduction in the overall temperature within the tunnel. When the mechanical smoke extraction system is integrated with the high‐pressure water mist system, therefore, it is feasible to integrate the high‐pressure water mist system with the mechanical smoke exhaust system in engineering applications.

As a clean fire extinguishing agent, water mist has been considered to be an alternative to Halon 1301 on shipboard. Recently, a new water mist system was designed for large shipboard machinery spaces. In order to test the fire suppression performance of this system, a full-scale shipboard machinery compartment having a volume of 1200 m3 was built. In this compartment, five fire scenarios, including diesel spray fires, diesel tray fires, and wood crib fires, were designed, and fire suppression parameters, including extinguishment time, compartment temperature, and gas concentrations, were measured. For all the scenarios, extinguishment times were typically less than 1 min, except for small fires. Average compartment air temperatures dropped to 70 °C within seconds after mist was activated. The CO concentrations of all the scenarios were below 4000 ppm, which was not life-threatening for short-term exposures. The test results indicated that this water mist system had an excellent ability to extinguish both obstructed and unobstructed Class B tray fires, Class B spray fires, and Class A fires in large machinery spaces. Meanwhile, the system could minimize the thermal damage to the compartment and its infrastructure and provide favorable conditions for personnel evacuation and firefighting. In conclusion, this newly designed water mist system was a viable alternative to Halon 1301 system for protecting large machinery spaces.

Recent efforts to investigate car-park fires and understand the related mechanisms have fostered the need for analyses of suppression performance against this type of fire scenario. This work aims at providing an insight into the ability of sprinklers and water-mist systems to control and extinguish a fire within an enclosed car park through a series of real-scale experiments. Three cars were employed in each test: the central one was ignited by a heptane pool fire and the adjacent ones served as targets. Two configurations were explored: in the first one, a nozzle was placed directly at the vertical axis of the ignition source, whereas the ignition source was located between the area coverage of four nozzles in the second one. The sprinkler system mainly served as a reference; two values of discharge density were evaluated for water mist at high operative pressure and a biodegradable surfactant was also tested against the most challenging configuration. A quantitative analysis of free-burn and discharge phases by temperature measurements was coupled with radiant heat-flux measurements and an assessment of post-fire damage. Sprinkler and water-mist systems were capable of containing the fire spread and thermally controlling the fire, thus preventing structural damage. The water mist’s ability to overpower the plume and reach the burning surfaces proved more effective than that of sprinklers, especially as no nozzles were located right above the ignition surface. The higher discharge density showed better capability of preventing re-ignition phenomena and suppression was attained in both the investigated configurations, which suggests that a certain amount of flux is also needed to achieve flame cooling. The additive had promising impact on suppression performance; however, more tests are required to specifically explore its ability to enhance thermal control.

6--personnel, endanger mission success and result in significant financial losses.To mitigate these risks, Automatic Fire Detection and Suppression Systems (AFDSS) are employed in military vehicles.Designed and tested in compliance with NATO's STANAG-4317 standards, these systems ensure rapid detection and suppression of fires across different threat levels.The STANAG-4317 categorizes fire hazards into fife levels each with specific protection requirements. Fire Levels and Protection Requirements Level 0 (No Protection Required)This level involves no protective equipment and serves only as a reference for environments where fire risks are negligible.--8--proposed AFDSS remains a critical enabler of mission success and vehicle survivability. Methodology Defining System Configuration and Design Based on Customer RequirementsIn military land vehicles, the placement of Automatic Fire Suppression Systems (AFSS) is tailored to the vehicle configuration and the specific requirements outlined by the customer.This phase is critical to ensuring an optimal system design and solution that addresses potential fire risks in various compartments.AFSS can be configured to protect key areas such as the driver's cabin, engine and transmission compartments, tires, fuel tanks and auxiliary systems like onboard generators.Each system is adapted to the customer's needs and the specific fire threat levels associated with each compartment.Following a thorough evaluation, suitable equipment is selected for each area to create a comprehensive system configuration that meets operational and safety demands.Key considerations for each protected compartment include:Driver's Cabin: Ensuring the safety of military personnel is the top priority.Rapid detection and suppression mechanisms are selected to safeguard lives in the event of a fire.Fuel Tanks and Power Units: Given their technical characteristics and potential hazards, detection and suppression systems are chosen for maximum efficiency in preventing or containing fires.AZoSensors. (2019, October 23).UV/IR detectors for flame detection -Principles of operation.Retrieved from https://www.azosensors.com/article.aspx?ArticleID=1327

The present research is using a Fire Dynamics Simulator FDS tool for computational design the fire spread anddistribution of fire exhaust particles. Therefore, knowing the program capabilities are very important for modelingthis problem. Nowadays, many different applications are using FDS, such as modeling for flow of smoke in differentventilation conditions, fires in tunnel and multi-floors buildings. The effectiveness of using various water mist flowrate amounts, different water mist particle sizes and two different fire source positions (corner and center) on the fireextinguishing time, are investigated through various scenarios of fire suppression by design and build a 1/5-scale ofwater mist system throughout FDS model “using PyroSim program", which shows a pronounced effected result. Thefirefighting time is reduced with decreasing the water mist droplet size (up to 30 μm). The fire suppression timedecreases as a result of increasing the flow rate of water mist spraying (up to 40 l/min).

The objective of the project is to develop water mist extinguishments design by scaling. The report describes the requirement and criteria of scaling fire, scale model, and the results of suppression for a developing water mist system design. The Maritime Safety Committee Draft Circular, MSC 914 is used as a basis test to evaluate a water mist design. A series of three full-scale tests related to MSC 914 were performed: fire only, fire with steel trailers, and fire with steel trailers and combustible commodities. A simulation was accordingly studied. Then, a scaled water mist design was tested in the scale model to find the characteristics needed for suppression in terms of pressure, water flow rate, droplet size, and the spray momentum. Based on these characteristics, a candidate nozzle will be selected for the full-scale MSC 914 test. The results so far show that the water mist system can effectively suppress the fire in scaled MSC 914 model. The full-scale MSC 914 is scheduled for September 2001. Therefore, the final answer is still pending until then. Scaling results are confirmed for temperatures, heat flux and flow for the MSC 914 fire without water add in.

A series of large-scale fire tests for road tunnel application was conducted in a test tunnel facility in Spain. The aim of this fire tests program was to investigate the magnitude of the heat release rate generated by a fire in heavy goods vehicles (HGV’s) with and without a fire suppression system in tunnels in Singapore; the possibility of interchanging a fire suppression system with other measures such as lowering the longitudinal flow velocity; and to acquire information on the appropriate design parameters (e.g., nozzle type, discharge density and activation time) to adopt based on the most probable fuel load used in these road tunnels. In order to ensure repeatability, simulated HGV’s consisting of 228 pallets with 48 plastic pallets (20%) and 180 wooden pallets (80%) were used in all fire tests. An air velocity of approximately 3 m/s was applied. As the scope of work covered in this fire test program is very large, only the setup of the fire test and the findings on the effects of heat release rate with (Test 4) and without (Test 7) a fixed water based fire-fighting system are covered. The test results indicate that a substantial reduction of fire heat release rate can be obtained using a low-pressure deluge fire suppression system, as long as timely activation of the water is provided. However, the influence of the suppression system on CO production is significant. Such experimental data address the current dearth of knowledge on the actual effect of low-pressure deluge systems on the heat release rate from HGVs in tunnel fires.

The possibility of trade-offs in road tunnel design incorporating suppression has been evaluated. Different tunnel configurations and ventilation conditions is considered to identify potential trade-offs, offering options of design alternatives for future substantial cost-benefit savings. Suppression systems are regularly used in Australia and Japan, and the interest regarding suppression systems in tunnels are growing in the rest of the world and slowly getting implemented in tunnels in Europe and other continents. Due to changes for instance in research regarding the acceptable design fire size and the growing focus on the fire safety in tunnels in general around the world, there is an opportunity of introducing trade-offs in tunnel design incorporating suppression systems. Possible trade-offs has been identified and outlined using risk based comparison approach as part of an evaluative process considering relevant safety objectives. Reliability of suppression systems is shown to be an important aspect, as well as the behavior of tunnel users. One may argue that suppression systems should always be considered as a primary option in tunnel design to achieve a desirable level of safety, enable fire brigade intervention and limit any costs associated with a tunnel fire. As an additional benefit to suppression systems offer the opportunity of potential trade-offs, opening a window of more innovative solutions and cost-benefit approaches compared to traditional prescriptive tunnel safety design. Residual value of this evaluative work and its conclusions shows that, when incorporating trade-offs, aspects like ‘point of no return’, visibility and consequences of trade-offs in the event of suppression system failure must be addressed from a fire engineering and risk management point of view.

PurposeSince the earliest days of mankind, fire has been both a friend and a foe. Restaurant facilities, characterized by the use of fire in their daily activities, pose unique fire risks as large numbers of people may gather at one time to consume food. The objective of this paper is to present the development of a fire safety evaluation tool whereby existing restaurant facilities can be evaluated for the purpose of identifying and eliminating fire hazards, and meeting the minimum requirements of current legislation.Design/methodology/approachThe evaluation tool has been developed by synthesizing information collected from an extensive literature review, principally of North American and UK based literature. The authors found it necessary to review causes of fire accidents in restaurants, and the materials and equipment involved in ignition. The paper also reviews restaurant requirements for fire detection and notification systems, fire suppression and extinguishing systems, and means of egress and evacuation systems.FindingsThe evaluation tool consists of 66 items to assess fire hazards, detection and notification systems, suppression and extinguishing systems, means of escape and management, and maintenance measures.Originality/valueThe paper provides a practical focus for property and/or facility managers responsible for day‐to‐day business operations of restaurant facilities and for surveyors inspecting such properties.