The effect of fire fighting foams on the environment and fire extinguishing (original) (raw)
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The Environmental Impacts of Fire-Fighting Foams
Research Papers Faculty of Materials Science and Technology Slovak University of Technology, 2010
The Environmental Impacts of Fire-Fighting Foams Extinguishing foams are commonly used for extinguishing the fire of flammable liquids, whereby their insulating, choking and quenching effects are exploited. The purpose of the paper is to consider and compare the foams currently used in fire departments, regarding mainly their high extinguishing effect (capability of faster aborted burning on the large surface at low foam consumption), but also their impact on the environment in each stage of their life cycle.
Safety & Fire Technology, 2020
Aim: The purpose of this article is to evaluate the extinguishing efficiency of water, compressed air foam and gel forming agents in solid materials fires. Project and methods: Comparison of the efficiency of extinguishing water, gel forming agents and compressed air foam was performed by conducting an experimental study to determine the appropriate indicator. An experimental device of the compressed air foam system was used for the study. The model fire of class 1A was selected as the fire. Comparison of extinguishing compounds was evaluated by extinguishing efficiency indicator I e.e. There were two experiments, with three series in each. Results: Extinguishing efficiency indicator I e.e took into account the time, and the mass of extinguishing agents needed to extinguish the model fire. Therefore, it was established that the mass of the compressed air foam used for extinguishing is 6.1 kg, which is 47% less than the mass of water used for extinguishing the test fire. With respect to the gel forming agent, the mass required for quenching was equal to 6.53 kg. This is 45% less than the weight of water and 2% less than the mass of compressed air foam. With respect to the quenching time, the greatest amount of time was observed for water. Time required for extinguishing (τ) amounted to 99 seconds. This value is 39% greater than the time it took to quench the flames using gel forming compounds, which was equal to 60 seconds. The minimum time required to extinguish the model fire (τ) was observed for compressed air foam, and was found to be 55 seconds. This is 45% less than that for water and 10% less than the time recorded for gel forming agent. Therefore, it was found that the fire extinguishing efficiency of compressed air foam is more than 80% higher than the water's, and 15% higher in relation to gel forming agents. Conclusions: The authors analysed fire extinguishing agents that can be used to extinguish solid combustible substances. Experimental studies with standard model A fires let them to determine a quenching efficiency indicator I e.e. Compressed air foam was found to have the highest fire extinguishing efficiency compared to water and gel forming agents. The advantages of compressed foam are due to the technology of its formation. Such foam has a high cooling and insulating ability, which is well reflected in its fire extinguishing efficiency compared to other extinguishing agents. Keywords: extinguishing efficiency, class A fire, water, CAF, gel Type of article: original scientific article
Advances in forest fire research, 2014
Introduction: The effectiveness of the foams used in fighting against forest fire depends on common effect of some coefficients. Cooling and isolation effects as main extinguishing effects as well as side extinguishing effects, like evaporation, blanket and separation effects are also included. Under the same conditions, the more extinguisher remains on the surface, the more extinguishing effect it has. Methods: A product for the test was randomly chosen out of the ones on the market. Spruce was chosen for the test due to its high flammability. The goal was to determine the amount of extinguisher at the end of the branches in the foliage. Groups of the same size were created in the selected foliage. To start with, the weight of the untreated foliage was measured, followed by the groups of foliage dipped in water and foaming agents. Results and discussion: According to the findings of research, the amount of foam remaining on the foliage is remarkably higher than that of water. Its rate is 3.36-3.76 compared to water. The research also revealed that this rate does not significantly depend on expansion rate. As a result, the fire intensity which can be extinguished by using foams expands as well.
The basic characteristics of foam concentrates application rate and their flow rates for fire fighting to extinguish tank fire are briefed. It is pointed out that the present fire fighting systems of large scale crude oil storage depots cannot meet the need to extinguish tank fires. In petroleum refinery, various hydrocarbons, both liquid and gaseous are handled. These hydrocarbons are flammable and explosive in nature and volatile to varying degrees depending upon their operating conditions. As the process operations are carried out at elevated temperatures and pressures, they offer high risk of fire and explosions and therefore it is imperative that proper safety precautions are taken in carrying out operations safely and prevent incidence of fires and explosions. This paper covers the application rate and flow rates of foam onto a fire is normally expressed as the amount of foam solution, in litres per minute, to be applied to every square metre of the total area to be covered with foam.
2014
III ACKNOWLEDGEMENTS V TABLE OF CONTENTS VII LIST OF FIGURES X LIST OF TABLES XII NOMENCLATURE XIII ACRONYMS XV CHAPTER ONE: INTRODUCTION 1 1.1 POLYURETHANE FOAMS AND FIRES 1 1.2 MOTIVATION 5 1.3 RESEARCH OBJECTIVES 7 CHAPTER TWO: LITERATURE REVIEW 10 2.1 POLYURETHANE FOAM PRODUCTION 10 2.2 FLAME RETARDANTS MECHANISMS IN RIGID POLYURETHANE FOAMS 11 2.2.1 Brominated Flame Retardants 14 2.2.2 Phosphorus Flame Retardants 20 2.2.3 Intumescent Flame Retardants 23 2.3 SUMMARY OF WORK TO DATE ON FLAME RETARDED RIGID POLYURETHANE FOAMS 25 2.4 STAGES OF FIRE DEVELOPMENT 28 2.4.1 Stage I: Thermo-oxidative pyrolysis 31 2.4.2 Stage II: Fully Developed Fires 38 2.4.3 Stage III: Post Flashover Fires 40 2.5 FIRE PERFORMANCE CHARACTERISTICS 41 2.6 COMBUSTION PRODUCTS 45 2.6.1 Smoke Products 47 2.6.2 Principal Fire Gases 50 2.6.2.1 Reduced Oxygen Concentration (O2) 53 2.6.2.2 Carbon dioxide (CO2) 53 2.6.2.3 Carbon monoxide yield (CO) 54 2.6.2.4 Smoke Toxicity Index (CO/CO2) 54 2.6.2.5 Nitrogen Oxide...
Fire Behaviors of Polyurethane Foams
2015
The effect of using flame retardant (FR) additives in polyurethane (PU) foam has been investigated using a cone calorimeter at 30 kW/m. Peak heat release rate was found to increase for normal foam as compared to FR foam. Carbon dioxide was found lower for FR PU foam, whereas carbon monoxide yield was found to be very high as compared to PU foam. Smoke toxicity, as indicated by the index of combustion completeness, was found to be higher for PU FR as compared to PU foam.
Advances in forest fire research, 2014
Introduction: Aerial firefighting is a very expensive solution; however bombing just pure water is not always enough to suppress the fires. In many cases retardants or special agents are added to water to increase efficiency, wetting it or creating foam. Methods: This research used dried pine wood pieces as samples. Samples were divided into different groups: not treated samples for giving the reference data or treated samples to ensure data for calculating the isolation effect of foam. During the experiment with a randomly chosen foam agent product a 3% foam solution was mixed. From this solution 6-9-12 expansion rate foams were generated. Samples were also provided with a metal ring to ensure the exact depth of water or foam blanket. Each sample was put in a special heat oven which ensured the permanent 35 kWm-2 heat fluxes and measured the different ignition time. Results and discussion: Experiment demonstrated that the ignition times in case of foams are longer than in case of same equivalent pure water. The longer ignition time of foams can be expressed by the pure water amount. Results say that the maximum rate of isolation effect in value of water equivalent is more than 2.3 but always significantly more than just pure water.
Phenomenological Model and Experimental Comparisons on Static Foam Drainage for Fire Fighting Foams
Fire Science and Technology, 2016
This paper is concerned with the development of a phenomenological model for drainage from static foams used in standard fire-foam qualification tests for low expansion ratio commercially available foams. The fact that operational foam heights (30 mm) are much smaller than foam drainage apparatus heights (200 mm) has been the inspiration to determine the height dependence of static drainage. This is done by constructing a model of foam drainage based on momentum flux balance and conducting experiments with an apparatus with foam drainage through a fuel layer. The results show a linear relationship of quarter drainage time with the height consistent with the theoretical expectations. The constants are related to viscosity and liquid film thickness. Microscopic examination on bubble movement and the pictures are used to infer that the bubble size distributions between three commercial foams are not distinctively different and so are the film thicknesses. It is argued that the strong dependence on quarter drainage time on the film thickness can be consistent with the experimental results only if the variation of these thicknesses between different foams is not significantly large. Assuming a constant film thickness, the constants of the relationship between quarter drainage time and height are obtained from the experimental data. The constants derived from the experimental data show dependences in which lower concentration foams have a behavior different from those with higher concentrations beyond known influences of viscosity and surface tension. The need for longer duration drainage as a qualifying measure is argued to be important to correlate with fire extinction behavior.
Chemical Engineering and Science, 2014
Aqueous film-forming foams (AFFFs) are among the most popular fire-fighting foams used in liquid fuel fires because of their film forming and fast knock down property. One key ingredient of AFFFs, the fluorocarbon surfactant i.e. perfluorooctane sulfonate (PFOS) which is used to reduce surface tension and positive spreading coefficient, is toxic to aquatic life and is a persistent chemical that accumulates in the blood of humans and other animals. Surfactants are not found naturally in the environment and are man-made. In the year 2000 unexpectedly announcement of phasing out fluorocarbon surfactant's manufacturing and its storage which effected a number of product lines, including the firefighting foams. Internationally the manufacturing and release of PFOS to the environment will be suspended by 2015. New fluorosurfactants have been introduced into the market with reformulation and used to form aqueous fire-fighting foam concentrates. The toxicity of the new fluorosurfactants and their persistence in the environment are not well established and still are under investigation. Their presence in the future market is unsure. The continuous research and development to find out the substitute for perfluorooctane sulfonate derivative (C8) has brought two choices i.e. Fluorine-free foams or Fluorotelomer (C6)-based Foams. These foams which may fulfill requirement of different international standards of fire fighting but still contain small amounts of fluorochemicals and are thus not truly fluorine-free. There is every possibility that even after 2015 new regulation may come in to effect to restrict the use of these new formulations (C6) of fire fighting foam. Therefore, the fire-fighting industry has an urgent need for new, environmental friendly foaming agents and foam stabilizers to replace fluorosurfactants in aqueous fire-fighting foams with enhanced drain time, low bubble coarsening, and faster knockdown and excellent burn back resistance properties.