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The use of external fire suppression systems can reduce the risk of fire spreading between buildings. This study investigated the effectiveness and efficiency of different externally placed water-based fire suppression systems on façade fire safety. A series of large-scale experiments comprising an SP Fire 105 setup equipped with sprinklers and high-pressure water mist nozzles have been performed. A combustible façade, consisting of 2.5 cm thick oriented strand board (OSB) plates, was installed to provide challenging conditions and allow a visual assessment of the post-fire damage. The temperature profile on the façade surface was measured with 34 thermocouples, while five heat flux gauges and two fast-response plate thermocouples were used to measure the heat flux on the façade surface and emitted to the ambient. The sprinklers and the high-pressure water mist system effectively suppressed the upwards flame migration and reduced the heat flux toward adjacent buildings. It was observed that the sprinklers acted as a water curtain and kept the façade wet during the fire, promoting minor damage (the burnt area is less than 1% of the total area). The temperature and heat flux measurements demonstrated that the sprinkler system was the most effective suppression system. However, the high-pressure water mist systems achieved similar effectiveness but a much higher efficiency concerning water consumption. The sprinkler nozzles used four times as much water as the high-pressure water mist nozzles. [ABSTRACT FROM AUTHOR]

As the complexity and the cost of infrastructures have risen, the need for a fast, reliable, cost-effective and clean fire extinguishing system has become important. Water mist is a clean and effective technology to deal with most types of fires. Over the years, chemicals have been added to the water to improve the performance of the mist and deal with new types of fires. This review presents an exhaustive state of the art on additives for water mist technology over the last fifty years. Eleven publishers were reviewed to form the corpus of almost one hundred articles. A systematic review of the articles highlighted that alkali metal compounds have been the main focus of research. Metal-based compounds have also proved to be effective. Surfactants remain an additive of choice in the formulation of fire-fighting foams and as additives for water mist but hydrocarbon surfactants should be preferred to fluor-based ones for environmental reasons. Solvents have proved to be a new, clean and potent class of water mist additives worthy of further investigation. Overall, the toxicology and environmental impacts of most additives have not been addressed or are often overlooked as an important criterion for a water mist additive. [ABSTRACT FROM AUTHOR]

A previous investigation showed that fire in circular, mechanically-ventilated, horizontal 0.30-m and 0.61-m ducts could be extinguished effectively by discharging water mist in a co-flow manner with the exhaust flow. However, besides horizontal ducts, an exhaust system is likely to also have ductwork in vertical and other orientations. Since the water mist dispersion and transport to the fire could be affected by the duct orientation due to fire buoyancy, there was a need to determine if the established horizontal duct protections would also be applicable to other duct orientations. Considering the fact that the fire buoyancy effect in ducts is bracketed between horizontal and vertical duct orientations, a series of fire tests was therefore conducted to evaluate if the above-mentioned horizontal duct protections would also be applicable when the ducts were to be in the vertical orientation. This paper presents the evaluation of vertical duct protection employing the same nominal spacing of 0.31 m for the water mist application as for the horizontal duct protection. The evaluation included the two protections established previously for the horizontal 0.30-m duct: one provided a minimum water mist concentration of 300 g/m3 with a median droplet size of 77 μm, while the other provided 399 g/m3 with a median droplet size of 88 μm. On the other hand, the protection for the horizontal 0.61-m duct yielded a minimum water mist concentration of 270 g/m3 with a median droplet size of 115 μm. The vertical duct tests showed that, by discharging water mist upward in the co-flow manner with the exhaust flow, both the protections for the horizontal 0.30-m duct could successfully extinguish the fire in the vertical duct, but the protection for the horizontal 0.61-m duct could not completely extinguish the fire in the vertical duct when water mist was discharged upward in the co-flow manner. However, by discharging water mist downward against the exhaust flow, the fire in the vertical 0.61-m duct could be extinguished rapidly. The vertical duct tests showed that, to ensure the applicability of a water mist protection for different duct orientations, the protection should be verified for both the horizontal and vertical duct orientations, with appropriate adjustments if required. [ABSTRACT FROM AUTHOR]

The fire hazard resulting from the thermal runaway of lithium-ion batteries constitutes an severe threat for electric vehicles, and discovering an effective and prompt method for suppressing battery fire is still challenging. In this paper, a finite volume model for simulating the process of extinguishing lithium-ion battery fire was established, and the effect of water mist on suppressing battery fire was studied. It was found that the larger the droplet size, the greater the initial spray velocity, or the higher the nozzle height, the worse the fire extinguishing effect. The larger number of nozzles, the greater the spray flow, or the earlier the spray start time, the better the fire extinguishing effect. As the spray duration increased, the suppression effect at the center module gradually increased. When the water mist nozzle faced the center point of the module, the temperature rise was much lower than at other angles, and the fire extinguishing performance was the most effective. [ABSTRACT FROM AUTHOR]

The effectiveness of suppression of lithium ion battery, LIB, fires with water mist was investigated experimentally using a previously developed bench-scale wind tunnel. The experiments were conducted on lithium ion cell arrays constructed from twelve cylindrical (18,650 form factor), fully charged, lithium cobalt oxide cells, which were densely packed in a rectangular configuration without gaps. An electric heater was employed to initiate thermal runaway in one cell. Failure propagation was then tracked using thermocouples located at the bottom surfaces of the cells. Heat release due to flaming combustion was computed based on the oxygen consumption method. Experiments conducted at 640 l min−1 of air, 320 l min−1 of air, and 186 l min−1 of nitrogen tunnel purge flow were used as reference points. All reference point experiments underwent complete cascading failure. Addition of 1.0 and 1.6 g s−1 of water mist to 320 and 640 l min−1 of air produced agent concentrations of 14.1 and 11.1 wt%, respectively, which are slightly above the concentration of water mist recommended for suppression of traditional fires. Application of water mist at 1.0 and 1.6 g s−1 prevented cascading failure in 40% and 50% of the tests, respectively, and significantly reduced the rate of failure propagation in the other tests. At both water mist delivery rates, flaming combustion associated with burning of battery ejecta was inhibited, reducing the combustion efficiency below 50%. One of the key findings of this study is that suppression of flaming combustion is not sufficient to stop cascading failure. The array must be continually cooled with water mist until the temperature of the cells decreases below a certain threshold, which prevents chemical reactions between battery materials inside the cell casings. [ABSTRACT FROM AUTHOR]

CEN and NFPA have expanded the application of water mist in open environments from light solid combustible fire hazards to several in the higher hazard categories. A previous analysis and test evaluation showed that such application expansion is feasible, provided that the water mist spray meets droplet size and application density requirements for the intended fire challenge. However, this evaluation was performed exclusively for water mist sprays discharging at 1.65 m above the burning combustibles. This led to the question of whether the water mist protection could still be effective for larger clearances of nozzle discharge above the combustibles. Therefore, a series of fire tests was conducted subsequently to determine the ceiling height limits for both deluge and automatic nozzle protections. As for the previous evaluation, the two tested fire challenges were a 2-tier (2.74 m) high rack-storage of corrugated cardboard cartons on wood pallets, and a palletized storage of cartoned expanded polystyrene up to 1.68 m high. Both fire challenges were in the CEN OH-3 category, and respectively represented fire hazards in the FM Global HC-2 and HC-3 categories, which in turn corresponded to the NFPA OH-1 and OH-2 fire hazards. Each water mist spray discharged 76 l/min at 16.5 bar, with a volume median droplet diameter of around 220 µm. The nozzles were spaced 3.05 × 3.05 m to provide a designated application density of 8.1 mm/min. Quick-response thermal sensors, with an activation temperature of 74°C and a response index of 27.6 (m s)1/2, were employed to initiate the nozzle discharge. The tests showed that the deluge protection is applicable to both fire challenges for ceiling heights up to 9.1 m. However, for the automatic nozzle protection, the ceiling height limit is reduced to 6.1 m, with a water supply requirement of providing 17 nozzle operations for a safety factor of about 50% over the maximum number of nozzle operations observed in the tests. [ABSTRACT FROM AUTHOR]

Water mist-based fire-extinguishing systems are gaining acceptance for the protection of ship machinery spaces. The use of simulation tools presents a great potential for taking a performance-based design (PBD) approach to these fire scenarios. The Fire Dynamics Simulator (FDS) is the most frequently used and validated fire modeling software; however, studies of low-pressure water mist fire suppression modeling in ship engine rooms are rare. This paper contributes to the current literature by using the FDS to model a series of fire suppression scenarios defined by the International Maritime Organization (IMO) Circulars, including spray and pool fires with heptane and diesel oil, as well as exposed and obstructed fires. The simulation results are compared to data from full-scale tests conducted at recognized fire testing laboratories. Furthermore, an analysis of both the experimental and model uncertainties is carried out to assess the simulations performance. In general, a good agreement in compartment temperature evolution and fire extinguishing time is found for the modeled fire scenarios. The results support the application of FDS in a PBD approach for the design of water mist fire extinguishing systems for machinery spaces in ships. In this way, designers and engineers could model different machinery volumes and nozzles spacings that differ from those prescribed for a one story square engine room of the IMO, and, thus, predict the evolution of temperatures and extinguishing times for get the authorities approval. [ABSTRACT FROM AUTHOR]

Water mist fire fighting has achieved a well established position in fire protection for industrial and civil applications. The performances of water mist nozzles, largely used in water mist production, are deeply influenced by the internal nozzle flow characteristics and CFD modelling is a powerful tool to analyse them in details. The paper focuses on the numerical investigation of the internal flow in pressure swirl injectors for water mist applications. 3D large eddy simulations based on the Volume-Of-Fluid methodology have been implemented. The flow is assumed to be incompressible and under isothermal non-reacting conditions. Validation of the model against available experimental data is performed with satisfactory results. The effect of internal nozzle geometry on the injector behaviour is investigated by modifying the inclined swirling channels (five configurations) and the injection pressure in the range 5 to 320 bar. The effect of the size of cylindrical and conical swirl chambers are also independently investigated. Three different flow regimes can be distinguished as a function of imposed swirl and injection pressure and a map is reported to clarify the effect of these parameters. When a stable hollow cone spray is formed the mass flow rate fluctuations are < 5%, corresponding to a discharge coefficient between 0.34 and 0.50. When no air core is present in the discharge hole, mass flow rate fluctuations as high as 16% are observed, which correspond to discharge coefficient as high as 0.7. A detailed quantification of in-nozzle characteristics, like swirl number and momentum flux distribution along the nozzle and lamella thickness in the discharge hole, is reported and discussed, with particular emphasis on stability and transient behaviour of the atomiser internal flow, which represents the main novelty of the present study. [ABSTRACT FROM AUTHOR]

Suppression of high-voltage (HV) electrical fires is difficult because it requires fire-extinguishing agents with good isolation properties as well as high fire-suppression efficiency. In the work presented herein, water mist with and without various water mist additives (WMAs) was utilized to suppress HV transformer oil fires. The WMAs included ionic alkali-metal salt and fluorocarbon surfactant, and nonionic hydrocarbon and fluorocarbon surfactants. At the same concentration, the surfactants were more efficient at extinguishing fires compared with the alkali-metal salt. The fluorocarbon surfactant was more efficient at extinguishing fires than the hydrocarbon surfactant, achieving flame extinction in 18 % of the time required when using natural water (NW). Besides, the effects of WMAs on the insulating properties of the water mist were studied. The gap breakdown test showed that the NW mist could increase the breakdown voltage of air by up to 5 % at 70-cm gap distance. Comparatively, the nonionic WMAs did not affect the insulating property of the NW mist, with the mist containing 1.0 % ionic KHCO3 solution enabling a reduction of up to 16 % in the breakdown at 70-cm gap distance while increasing the leakage current of the simulated insulator by up to 250 % at its nominal voltage. Finally, field tests were performed where NW mists were discharged onto a charged 220-kV high-voltage transformer. This study proves that NW mist and mists with nonionic WMAs are suitable for protecting HV electrical equipment, having important implications for extending the applications of water mist. [ABSTRACT FROM AUTHOR]

Recent research has shown that acoustics can be used to suppress flames from a liquid fuel source. The results of these experiments indicated that acoustics alone are insufficient to control flames beyond the incipient stage. Recent research has also shown that variations in the delivery of water mist to a fire can enhance the mist’s efficiency. Therefore, the addition of acoustics to water mist may be an effective means of enhancing an established fire protection technology. For the first time, acoustics and water mist have been combined and studied as a flame suppression strategy. A series of experiments were conducted that explored the potential for coupling acoustics with water mist as means of flame suppression. Heptane fueled flames were created from two different sized ceramic fiber wicks: 30 mm × 50 mm with 5 mL of fuel, and 60 mm × 100 mm with 20 mL of fuel. The flames were then exposed to water mist delivered at a constant rate, which was found to be incapable of suppressing the flames. Next, low frequency sound waves at 62 Hz and 80 Hz were used to suppress flames from both wicks, with each frequency being generated by a different resonator. Finally, acoustics from both resonators were combined with water mist, and used to suppress flames from both wicks. The results showed that a combination of acoustic waves and water mist suppressed the flames more effectively than each individual technique on its own. This finding opens the possibility of developing more efficient ways to use water mist technology. [ABSTRACT FROM AUTHOR]

An investigation was conducted to determine the feasibility of extending the total flooding water mist protection previously developed for a 7.47 × 7.47 × 7.47-m ignitable liquid dispensing facility to a larger building, for a longer but acceptable fire extinguishing time. The targeted building height and door opening were 7.62 m and 3.81 × 3.81 m, respectively. Same as for the 7.47-m cubic facility, the fire challenge was the combination of a cascading heptane fire spilling from the top of a fuel tank and the resulting shielded pool fire on the floor. The Froude-based scaling methodology and a well-stirred reactor model were used to assess the maximum building size and associated water mist requirement for a 0.48-scale mockup of the 7.62-m high facility, under the constraint of meeting the designated fire extinguishment time. A series of fire tests was then conducted in the 0.48-scale mockup to verify that the fire could indeed be extinguished within the designated duration for the determined building size and protection requirement. In general, it took less time to extinguish the fire as the water mist discharge rate was increased. The water mist sprays deployed in the door opening tended to reduce the fire extinguishment time by reducing air flow through the door opening, but not significantly in this investigation. However, the deployment of water mist sprays in the door opening is highly recommended to confine the spill fire within the protected building. The tests also showed that it took longer time to extinguish the fire as the fire was closer to the door opening. Based on the 0.48-scale test results and scaling relationships, the water mist protection requirement and corresponding fire extinguishment time for the 7.62-m high facility were projected for a building floor area of 580 m. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

This work focuses on interactions between a water mist and a smoke layer generated by a fire. It aims at highlighting and quantifying the mist impact on smoke stratification, investigating both thermal and optical effects. The study is based on large-scale experiments and numerical reconstruction with the computational code fire dynamics simulator (FDS v.6). The use of FDS allows understanding the complicated flow generated by the water mist and the fire, which yields specific gas temperature and opacity conditions within the medium composed of soot and water droplets in suspension. There are two main results. As expected, a de-stratification occurs as a consequence of mist application. A 1 m high smoke-free layer was observed in the present case before mist activation, which disappears due to the mist action. However, consecutive effects on optical and thermal properties are not identical. In the presented tests, water mist application homogenized the gas temperature downward the nozzle location to a value close to 50°C due to both mixing and cooling effects (while temperature was varying between ambient temperature near the floor and 150°C below the ceiling before mist activation). On the contrary opacity measurements revealed remaining discrepancies, in soot and droplet concentrations. Transmissivity decreases after mist activation, but significant variations are still seen in the smoke layer. As a consequence, characterization of the smoke layer with one single technique or the other (namely: opacity measurement or temperature measurement) would lead to different conclusions on the smoke homogeneity. It appears that both measurements should be involved simultaneously for a complete characterization of the environment. [ABSTRACT FROM AUTHOR]

In fire safety engineering, when codes and standards do not provide a good solution performance-based design appears the most effective approach to design protection systems for civil buildings and infrastructure. This circumstance often occurs for historical buildings under renovation, for large or complex buildings and for tunnels. In particular, numerical simulations of fire scenarios including evaporating sprays are very interesting due to the fact they have a great potential to assess the effectiveness of sprinklers, mist systems and fire fighting strategies that aim to control or suppress combustion. To do that, a fundamental knowledge of the sprays used and behavior is needed to obtain a good understanding of the effects on fire and smoke. Spray parameters seem different for every model and, besides, results are grid dependent, so comparisons with experimental data are needed to assure consistency of the conclusions. In this paper, the main focus is on the validation and assessment of a high-pressure single fluid water mist nozzle upon droplet dispersion and evaporation rates in different ambient air conditions in terms of temperatures and air humidity. Through the validation of a numerical set-up in OpenFOAM, it is possible to minimize the uncertainty that affect the description of the scenario when predicting its effectiveness in fire simulations. [ABSTRACT FROM AUTHOR]

The paper deals with interaction between water mist and hot gases in a longitudinally ventilated tunnel. The work aims at understanding the interaction of mist, smoke and ventilation.The study is based on one intermediate tunnel test and an extensive use of the computational code Fire Dynamics Simulator (FDS, NIST). The approach consists first of reconstructing the test with the CFD code by defining the relevant numerical parameters to accurately model the involved water mist system. Then, it consists of handling from the local data the complicated flows generated by the water mist flooding on the one hand and by fire and ventilation on the other hand. The last stage consists in quantifying each mechanism involved in interaction between water mist and hot gases. There are three main results in this study. Firstly, the CFD code prediction is also evaluated in this configuration, with and without water mist. Before the mist system activation, the agreement is satisfactory for gas temperatures and heat flux. After the activation time, the CFD code predicts well the thermal environment and in particular its stratification. Secondly, water mist plays a strong thermal role since in the test studied, roughly half of the heat released by fire is absorbed by water droplets. Thirdly, heat transfer from gaseous phase to droplets is the main mechanism involved (73%). The remaining heat absorbed by droplets results from tunnel surface cooling which represents (9%) and radiative attenuation (18%). [ABSTRACT FROM AUTHOR]

This paper describes work done to improve and validate the capability of fire dynamics simulator (FDS) to predict the dynamics of water mist sprays. Three single orifice and five multi-orifice spray heads are modeled with FDS based on information on the flow-rate, spray angle, operating pressure and experimentally determined particle size distribution. The capability of FDS to predict the drop size, velocity, mist flux and number concentration profiles within the spray cone is assessed. The effects of turbulence modeling on the predictions of the spray dynamics is investigated. The capability of FDS to predict the air entrainment by high-speed water sprays is validated using experiments in rectangular channels with open ends. [ABSTRACT FROM AUTHOR]

Fire protection practices for highway tunnels have been undergoing significant changes in the last decade, largely in response to a number of catastrophic fires that caused tunnel authorities to thoroughly review their fire safety assumptions. One of the fire safety issues currently receiving much attention includes the installation of 'active' fire protection systems in addition to the 'passive' fire protection features that were until recently considered to be sufficient to mitigate fire risk in tunnels. Passive fire protection measures include the use of fire resistive construction materials which help protect the critical structural elements from damage due to high temperatures. Active fire protection systems include fixed piping systems to deliver water sprays, such as deluge sprinklers and water mist, or other water-based agents such as compressed air or high expansion foam (CAF or Hi-Ex respectively). Active fire protection systems for tunnels are currently referred to as water based fixed fire fighting systems, or FFFS for short. Fire research suggests that measures based solely on passive protection are not likely to be sufficient to protect life and property to the degree warranted by the high monetary and strategic value of modern tunnel infrastructure. Full-scale fire testing and engineering analysis indicate that FFFS have the potential to reduce the impact of a severe fire on the tunnel structure from catastrophic to manageable at an affordable cost. Fire testing with CAF and Hi-Ex foam systems has shown them capable of actually extinguishing very large fires, including hydrocarbon pool fires. Systems based on water sprays on the other hand are not expected to extinguish fires, but rather to control the fire, limit fire growth and heat release rate, prevent fire propagation and provide thermal management. Although there are a few years of experience internationally that have proven sprinkler and deluge sprinkler system to be effective in mitigating tunnel fires, recent testing of FFFS in Europe has concentrated on water mist. One reason is the perception that water mist systems may involve less complex piping and agent storage than CAF or Hi-Ex foam, and may provide equivalent or superior performance with less water and smaller pipes than conventional sprinkler deluge systems. However, many engineering challenges remain to be resolved, such as how much credit to grant to the FFFS in terms of reduced criteria for passive protection, and how exactly to integrate active protection systems with traditional fire safety measures such as the ventilation systems. This article examines some recent developments in understanding how active fire-fighting systems might alter the impact of fires in tunnels. [ABSTRACT FROM AUTHOR]

A computational, multi-phase, model has been developed to study the interactions between water droplets and radial expansion of a gas cloud in a spherical chamber. Initial conditions for the gas cloud are specified based on chemical equilibrium calculations for the detonation of a high explosive (RDX). Mono-dispersed water droplets are injected at uniform concentration into the chamber prior to the expansion. A Lagrangian model is used to track the breakup of the parent drops near the shock front to form child drops, which are extremely small. The Navier-Stokes solutions show that the child droplets accumulate near the shock front and evaporate at 100 times higher rate than the parent droplets. Latent heat absorption is the dominant mechanism followed by the sensible heat absorption by the water vapor (and droplets), and momentum absorption from the high velocity gases by the child droplets. The simulations also show that the water vapor formed by the evaporation increases the gas density at the shock front. The increased density and reduced gas temperature (cooling) have opposite effects on the pressure at the shock front. This leads to only a modest suppression in the pressure. At realistic droplet concentrations (0.08 kg droplets/m of air), the water mist is shown to evaporate completely in a short time (2.42 ms) prior to shock reflection at the chamber wall mainly due to the breakup at the shock front. High concentrations of mist may be desirable, but are difficult to achieve in practice at the total flooding conditions. [ABSTRACT FROM AUTHOR]

The high cost of conducting large, full-scale fire tests for the evaluation of suppression systems in tunnels tends to limit both the extent of the instrumentation provided and the number of tests that are conducted. Because of the variability of the large fires, performance criteria based on single point measurements derived from experience with smaller test fires were not reliable indicators of performance. Yet decisions about the acceptability of suppression systems must be based on the limited amount of performance information available. A means was sought to reduce the reliance on single point instrumentation readings, and to augment the value of the limited amount of test data by integrating the field testing with CFD modeling. In this study a computational fluid dynamic (CFD) model was used to simulate a series of full-scale fire tests of water mist systems conducted in 2006 in a highway test tunnel. The NIST Fire Dynamics Simulator version 4 (FDS4) was used to simulate five of the tunnel fire tests. The task was to confirm that the simulations could achieve a reasonable degree of agreement with the conditions measured in the tests. The model could then be used to evaluate the performance of the water mist system over a broader range of performance indicators than were measured. This paper illustrates what is unique about very large fire tests and presents highlights of the modeling. The level of agreement between simulation and test results is demonstrated for one test. Agreement was deemed to be good enough to establish confidence in applying the model to examine the conditions that would occur with an unsuppressed fire, which had not been tested. CFD modeling can be used to improve the understanding of the performance of the suppression system, and to augment the value of the test results. A second, complementary paper has been submitted to the SFPE Journal of Fire Protection Engineering to provide more detailed information about the FDS4 modeling than can be covered in this paper. [ABSTRACT FROM AUTHOR]

Water-mist technology provides efficient fire suppression for compartments while minimizing water usage. Even with the many advantages of water mist systems, there is still room for improvement. Water mist systems have demonstrated effectiveness at suppressing flammable liquids (Class B) fires in compartments. However, an especially challenging fire suppression scenario for water mist systems is the small Class B fire. This scenario is often realized after a large fire has been reduced in size or ‘controlled’ by water mist. The small fire scenario is challenging because a small fire may not be able to generate enough vaporized water to displace sufficient oxygen for complete extinction. It should also be noted that even if the Class B fire is extinguished with a water mist system, re-ignition from the hot surrounding surfaces may occur at any time. In the present work, an additive is introduced into the water supply and its effect on the water mist suppression performance is studied. This ForafacTM additive is a specific formulation, which includes fluorinated surfactants for creating a robust fire suppression foam. The enhanced suppressant exiting the mist nozzle is dispersed in the form of small droplets (not as a continuous foam) similar to a pure water mist spray. However, these droplets create a foam blanket on the surface of the fire, which acts to isolate the fuel from the air. With this formulation, the efficiency of the water mist system is improved even on small fires and most importantly the re-ignition of class B fires is prevented. [ABSTRACT FROM AUTHOR]