INBR 1835 Vol I (FF) PDF - Chemistry of Fire

RESTRICTED INBR 1835 (I) TABLE OF CONTENTS CHAPTER 1 CHEMISTRY OF FIRE CHAPTER 2 THEORY OF FIRE EXTINGUISHER CHAPTER 3 GENERAL SAFETY AND FIRE PREVENTION CHAPTER 4 FIRE ALARM AND DETECTION SYSTEM CHAPTER 5 FIRE HAZARDS...

RESTRICTED INBR 1835 (I) TABLE OF CONTENTS CHAPTER 1 CHEMISTRY OF FIRE CHAPTER 2 THEORY OF FIRE EXTINGUISHER CHAPTER 3 GENERAL SAFETY AND FIRE PREVENTION CHAPTER 4 FIRE ALARM AND DETECTION SYSTEM CHAPTER 5 FIRE HAZARDS AND CONTROL CHAPTER 6 METHODS AND TACTICS OF FIRE FIGHTING CHAPTER 7 PERSONAL PROTECTION CHAPTER 8 FIRST AID FIRE FIGHTING APPLIANCES CHAPTER 9 MAJOR FIRE FIGHTING SYSTEMS CHAPTER 10 THE FIREMAIN AND ASSOCIATED FIRE FIGHTING EQUIPMENT CHAPTER 11 AIRCRAFT FIRES CHAPTER 12 FIRE FIGHTING AND FIRE PREVENTION IN SHIPS REFIT CHAPTER 13 FIRST AID RESTRICTED 1-1  RESTRICTED INBR 1835 (I) CHAPTER 1 CHEMISTRY OF FIRE CONTENTS TOPICS ARTICLE NO. Fire Introduction 0101 Classes of Fire 0102 Flame Temperature 0103 Fire Tetrahedron 0105 Oxygen 0106 Fuel 0107 Flash Point 0108 Fire Point 0109 Spontaneous Ignition Temperature 0110 Spontaneous Combustion 0111-0112 Heat 0113-0114 Transfer of Heat 0115 Heat of Combustion 0116 Specific Heat 0117 Free Radicals 0119 Chain Reaction 0120 Phases of Chain Reaction 0121 Combustion 0123 Combustion of Gases 0124-0126 Combustion in Liquids 0127 Combustion in Solids 0128 Types of Combustion 0129 Miscellaneous 0131-0137 Fire Growth in a Compartment 0138 Growth Stage 0139 Rollover 0140 Flashover Stage 0141 Fully Developed Fire Stage 0142 Decay Stage 0143 Effect of Fire in a Compartment 0144 RESTRICTED 1-2  RESTRICTED INBR 1835 (I) CHAPTER 1 CHEMISTRY OF FIRE Fire 0101. Fire is defined as a rapid self-sustaining oxidation process accompanied by the evolution of heat and light. Alternatively, fire is a chemical reaction between fuel and oxygen, in the presence of heat. 0102. Classes of Fire. There are five classes of fire based on the type of fuel that is burning. These are :- (a) Class A. In this class of fire, the fuel is a solid material, normally of an organic nature (compounds of carbon) eg. Wood, paper, cloth etc. In this class of fire, the combustion generally occurs with a formation of glowing members. This is the most common class of fire. (b) Class B. In this class of fire, the fuel is a liquid or liquefiable solid eg. Diesel, Petrol, Avcat etc. These liquids can be divided into two groups :- (i) Those that are miscible with water. (ii) Those that are immiscible with water. (c) Class C. In this class of fire, the fuel is a gas or a liquefied gas which include LPG, Methane, Propane, Butane, Acetylene, Chlorine, Ammonia, etc. This gas is produced as a result of a liquid spillage, liquid or gas leak. (d) Class D. In this class of fire, the fuel is a metal eg, Aluminium, Steel etc. (e) Class E. In this class of fire, there is an involvement of live electricity. Generally this type of fire gets converted in to Class-A fire, once the power supply gets switched off. 0103 - 0104. Spare Fire Tetrahedron 0105. The four components of any fire are Fuel, Oxygen, Heat and Free Radicals. These four components can be schematically represented by a Fire Tetrahedron (Fig 1.1). The significance of this tetrahedron is, that no fire is possible without the involvement of each of these four components. The removal of any one component, will extinguish the fire. RESTRICTED 1-3  RESTRICTED INBR 1835 (I) Fig. 1.1: The Fire Tetrahedron Oxygen 0106. Oxygen is a diatomic gas, which is freely available in atmosphere at a concentration of 21 %. Oxygen is a good supporter of combustion and reacts with almost all kinds of fuels, except inert gases. For the combustion to take place, a minimum oxygen concentration of 16 % is essential. Fuel 0107. Any material that can be burnt is termed as a fuel. The fuel can be in a solid, liquid or gaseous state. All the fuels are fire hazards because all of them will burn, provided the right conditions are generated. The degree of hazard of the fuel, is dependent on certain temperatures, which are defined in succeeding paragraphs. Flash Point 0108. It is the lowest temperature at which the fuel/liquid produces sufficient vapours to produce a flash, on the application of a naked flame. A flash is therefore caused by the ignition of the vapours only. However, this flash or the combustion reaction is not self sustaining and extinguishes on its own. Flash points of some of the commonly used gases and liquids are as given in Table 1.2 :- Ser Gas/ Liquid Flash Point (°C) (a) Gasoline - 45 (b) Kerosene 38 to 47 (c) Jet fuel 43 to 65 (d) Diesel 61 (e) Furnace fuel oil 90 (f) Vegetable oil 282 (g) Lubricating oil 232 RESTRICTED 1-4  RESTRICTED INBR 1835 (I) Table 1.2: Flash Points of Common Gases and Liquids Fire Point 0109. It is defined as the lowest temperature at which a liquid produces sufficient vapours to produce a self-sustaining fire, on the application of a naked flame. Spontaneous Ignition Temperature 0110. It is the lowest temperature at which the liquid produces vapours that ignite and burn, even without the application of a naked flame. This is also called the Auto Ignition Temperature (AIT). The Auto Ignition temperature of some of the commonly used gases and liquids are given in Table 1.3 :- Ser Gas/Liquid Auto Ignition Temperature (°C) (a) Gasoline 246 to 257 (b) Kerosene 254 to 260 (c) Lubricating oil 371 Table 1.3: Auto Ignition Temperatures of Common Gases and Liquids Spontaneous Combustion 0111. Certain materials, especially carbon based organic materials, react with oxygen at room temperature. Compounds such as linseed oil, which contain carbon-carbon double bonds, are very prone to this type of reaction. If such a material (fuel) is a good thermal insulator, the heat generated during such a reaction cannot escape and the temperature rises further. This further increases the rate of the reaction. Eventually, the auto ignition temperature of the fuel is reached and the combustion commences. Similarly, the action of few bacteria on certain organic materials can also cause a rise in temperature, eventually leading to active combustion. Spontaneous combustion can also take place in finely powdered coal and some metals. Many practical examples of the above phenomenon have been recorded in drying oils, haystacks and coal stores. The thermal insulation factor is of a great importance in this type of combustion. Cross linking of some plastics, may also lead to spontaneous combustion. 0112. The Flash Point, Fire Point and Auto Ignition Temperatures, for all the fuels onboard the ship, are to be known. However, the Flash Point is to be considered as the Danger mark for all fuels, due to the following reasons :- (a) It is the lowest temperature and does not give adequate reaction time. (b) Most fuels on board ships are stored in closed containers. Therefore, in case of a flash in a closed container, there could be an explosion that could cause a severe damage to the ship. RESTRICTED 1-5  RESTRICTED INBR 1835 (I) Heat 0113. Heat is a form of energy. Effects of heat on a material are:- (a) Increases the size. (b) Increases the pressure of the system subjected to heat (c) Changes in the physical state (solid - to liquid - to gas). (d) Produces a glow or luminosity or colour. (e) Generates small electric current (Thermo-electric effect) 0114. The temperature of the body indicates how hot or cold a body is. Whereas, the heat is the energy that can be utilised to work and can always be transformed into another form of energy. Transfer of Heat 0115. Heat travels from a point of high temperature to a point of low temperature. It travels by the following three modes:- (a) Conduction. This mode of heat transfer is seen in solids. The molecules vibrate about their fixed positions and heat transfer is effected from molecule to molecule. (b) Convection. This mode of heat transfer is observed in fluids (liquids and gases). The molecules closer to the heat source get heated, expand, become lighter (decrease of density due to expansion) and float upward and the heavier molecules come down to the source of heat. This mode of heat transfer where in the molecules are moving from one point to another is known as convection and the currents are known as Convection Currents. (c) Radiation. This form of heat transfer is through Electro Magnetic Radiations. These radiations travel through vacuum and there is no matter required. Radiations can be deflected, reflected or absorbed. Heat Of Combustion 0116. It is the amount of heat released during a substance's complete oxidation (combustion, i.e. conversion to carbon dioxide and water). Heat of combustion, commonly referred to as Calorific or Fuel Value, depends on the kind and number of atoms in the molecules, as well as their arrangement within the molecule. Calorific Values are commonly expressed in Joules per gram, but are sometimes reported in British Thermal Unit per pound (Btu/lb) or calories/g. (1 cal/g = 4.18 J/g and 1BTU= 2.326 KJ/Kg). The heat of combustion in KJ/Kg of some of the substances is as given in Table 1.4 :- Ser Fuel Heat of Combustion (KJ/Kg) (a) Wood (Oak) 16700.68 RESTRICTED 1-6  RESTRICTED INBR 1835 (I) (b) Paper 18335.86 (c) Charcoal 30051.92 (d) Alcohol (Ethyl) 29772.8 (e) Aluminium (Metal) 30935.8 (f) Lubricating Oil 47450.4 Table 1.4: Heat of Combustion of Some Common Fuels 0117. Specific Heat. It is the quantity of heat required to raise the temperature of one gram of substance through on degree centigrade. It is interesting to note that the specific heat of all other substances is less than that of water. Organic substances such as petrol, alcohol, etc. have low specific heat. This means that such substances, when exposed to a given quantity of heat, show a much greater rise of temperature than water - a factor of considerable importance from the point of view of fire propagation. Specific heats of some of the substance in calories per gram per degree centigrade are as given in Table 1.5:- Ser Substance Specific Heat (Cal/g/°C) (a) Water 1.0 (b) Lubricating Oil 0.51 (c) Wood 0.42 (d) Air 0.24 (e) Aluminium metal 0.217 (f) Iron metal 0.113 Table 1.5: Specific Heats of Common Substances 0118. Spare Free Radicals 0119. Modern science has accepted that there are `Free Radicals’ which form the fourth component of the Fire Tetrahedron. The details of this concept are enumerated in the succeeding paragraphs. Chain Reaction 0120. Consider the combustion of Octane. Octane is a graded fuel with a reasonably good calorific value and it combines with oxygen to give carbon-dioxide and steam. The chemical reaction is as follows: - C8H16 + 12O2 8CO2 + 8H2O Explaining the reaction by the Collision Theory, it would mean that one molecule of Octane collides with twelve molecules of oxygen and forms eight molecules each of steam and carbon-dioxide. However, studies have proven, that irrespective of the concentration or the energy levels of the fuel, in a reaction, not more than 3-4 molecules can be involved in a collision simultaneously. Therefore, the above reaction cannot take place in a single step, but takes place in several stages. In the first stage, the octane molecule may react with one to three molecules of oxygen as shown :- RESTRICTED 1-7  RESTRICTED INBR 1835 (I) C8H16 + O C8H15 + OH C8H16 + 2O C7H15 + OH + CO C8H16 + 3O C7H15 + OH + CO2 The products of this reaction are highly unstable due to their incomplete molecular structures. Since the activation energy levels of these products are very low, they will react immediately in the next stage i.e. before the next molecule of octane can react. Thus the reaction is completed in stages. This sort of a reaction, which proceeds in stages, with the formation of highly unstable intermediate compounds, that react in the very next stage and take the reaction to completion, is known as a Chain Reaction. All fires are necessarily chain reactions and the intermediate compounds are Free Radicals. Phases of Chain Reactions 0121. All Chain Reactions consist of the following three phases: - (a) Initiation Phase - Formation of Free Radicals (b) Propagation Phase - Reactions involving Free Radicals (c) Termination Phase - Exhausting of all the Free Radicals 0122. Spare Combustion 0123. Combustion is the process of fire. It is the process of chemical reaction of a fuel with oxygen. This process is dependent on the physical state of the fuel. The processes of combustion, for different states of fuels, are outlined in the succeeding paragraphs. Combustion of Gases 0124. Random Brownian Motion. The molecules/atoms of any gas in a container are in a state of constant motion. The direction of the motion is random i.e. it is unpredictable. In the process of motion, the molecules collide with one another and with the walls of the container. These collisions may be elastic (no transfer of energy) or they may be inelastic collisions (transfer of energy). If the molecules are in a state of random motion and the resulting collisions are elastic, such a motion is called Random Brownian Motion. 0125. Combustion Reaction. When a mixture of fuel in a gaseous state and oxygen, are in a container, the molecules are in Random Brownian Motion at low temperatures. When energy is supplied in the form of heat, the Kinetic Energy (velocity) of the molecules increases and the molecules collide with one another, with greater impact. When the velocities of the molecules cross a certain threshold, the collisions are no longer elastic (transfer of energy takes place), which results in the breaking down of existing nuclear bonds and formation of new bonds. This marks the commencement and therefore the propagation of the combustion reaction. Therefore, for any gaseous fuel to react with oxygen, the molecules of the fuel must have inelastic collision with those of oxygen. RESTRICTED 1-8  RESTRICTED INBR 1835 (I) 0126. Activation Energy. Activation Energy for a chemical reaction, is defined as the minimum energy to be possessed by the reactants, for the reaction to take place. Combustion in Liquids 0127. All flammable liquids, on heating, produce vapours. It is the vapour that burns and not the liquid. The combustion of these vapours has been explained in the preceding paragraphs. Combustion in Solids 0128. Solid fuels change into gaseous state, either through liquid state (by melting) or directly by sublimation. These vapours thereafter, follow the process of combustion, as described above. Types of Combustion 0129. Combustion can be classified into two types as: - (a) Type I. In this type of combustion, direct oxidation of combustible gases, liquids or solids takes place. The fuel does not undergo decomposition or pyrolysis in order to oxidize or burn. The temperature of the substance is raised to its ignition temperature and it undergoes oxidation. E.g. Methane (CH 4), Acetylene (C2H2), Alcohol (C2H5OH), Charcoal etc. (b) Type II. In this type of the combustion, the molecules of the substance breakdown or pyrolyse, under the influence of heat, to produce simple combustible gases and solids. These gases /solids unite with the oxygen in the air resulting in combustion. Almost all solids and liquids having Carbon, Hydrogen or both, burn by pyrolysis. Eg, wood, paper, paints, plastic, rubber and cooking oils etc. 0130. Spare Miscellaneous Terms 0131. Thermal Run-Away. When the temperature of the fuel is raised above the auto-ignition temperature, the energy released by the reacting molecules is sufficient to activate even larger number of molecules, which results in an higher rate of production of heat energy. The temperature rises rapidly resulting in a thermal run-away. The thermal run-away thus becomes a Flaming Combustion (a Thermal Explosion). 0132. Flash Over. In a uncontrolled compartment fire, there comes a stage where the total thermal radiation from the fire plume, hot gases and hot compartment boundaries causes the radiative ignition of all exposed combustible material and surfaces within the compartment. This sudden and sustained transition of a growing fire, to a fully developed fire, is called a Flash Over. RESTRICTED 1-9  RESTRICTED INBR 1835 (I) 0133. Lean Flash Over and Combustibility of Smoke. When a fire starts in a compartment, the heat given off decomposes the combustible material faster than it can burn. The smoke, full of fuel, rises to the deck-head and on further increase in the temperature, it reaches its ignition temperature causing combustion. This is known as Lean Flash Over. As the fire runs across the deck-head it radiates heat downwards, decomposing the other combustible substances within the compartment, thereby causing Secondary Fires. 0134. Backdraught. A fire in a compartment, which has limited ventilation, can produce gases containing significant proportions of a partial combustion products and un-burnt pyrolysis products. These gases accumulate within the compartment and on admission of air (by opening of a door/hatch), can lead to a sudden deflagration. This deflagration, which moves through the compartment and out of the opening, is termed a backdraught. This phenomenon is especially hazardous to the initial fire fighting parties trying to enter the compartment. 0135. Delayed Backdraught. In the event of a smouldering deep seated fire, the formation of a carbonised layer on the burning material and the oxygen deficient environment in the compartment causes the fire to be extinguished. When the door/hatch of the compartment is opened for fire fighting, air entering the oxygen deficient environment, alters the fuel ignition limit from the rich mixture towards the ideal mixture, but ignition (backdraught) does not take place not immediately. However, when the carbonized layer of a smouldering fire is disturbed, either by a length of hose or by moving of the smouldering furniture etc, the ignition source gets revealed and causes a backdraught. This is known as the Delayed Backdraught. 0136. Boil Over. It is a phenomenon in liquids with wide boiling range, like Furnace Fuel Oil. During the fire in an oil tank containing such liquids, the fractions which are light (having low density) burn at surface. These become heavy on burning and sink. The heat is thus transferred to the fractions which are present down below and they in turn move up, setting up a circulation. If water is present in the tank or used for fire fighting, it will steam and force the contents of the tank upwards, with an explosive expulsion. This phenomenon is called as the Boil Over. 0137. Slop Over. It is the formation of emulsion of fuel and expanding water (steam) or foam. The froth issues out from the open space in tank, and removes volumes of hot fuel. COMPARTMENT FIRE DYNAMICS Fire Growth in a Compartment 0138. During its life, a compartment fire normally experiences four different stages: growth, flashover, fully developed fire and decay. (Fig 1.2) RESTRICTED 1-10  RESTRICTED INBR 1835 (I) Fig 1.2: Fire Growth in a Compartment Growth Stage 0139. In the growth or a pre-flashover stage the average space temperature is low and the fire is localized in the vicinity of its origin. High local temperatures exist in and around the burning material(s), and smoke from the fire forms a hot upper layer in the space. (Fig 1.3) Fig 1.3: Growth Stage Rollover 0140. Roll over is the formation of a flame front of burning gases across the overhead of a space. Rollover takes place in the growth stage when unburned combustible gases from the fire mix with fresh air in the overhead and burn at some distance from the seat of fire. Rollover differs from flashover in that only the gases are burning and not all the contents of the space. RESTRICTED 1-11  RESTRICTED INBR 1835 (I) Flashover Stage 0141. Flashover is the period of the transition from the growth stage to the fully developed fire stage. Flashover occurs in a short period of time and may be considered as an event, as ignition is an event. It normally occurs when the upper smoke layer temperature reaches 600°C and the radiant heat flux at the deck reaches 20 kW/m2. The most obvious characteristic of flashover is the sudden spread of flame to all remaining combustibles in the fire space. Survival of personnel who have not escaped from the compartment prior to flashover is unlikely. Fully Developed Fire Stage 0142. In the fully developed or post-flashover fire stage, all combustibles in the space have reached their ignition temperature and are burning. During this stage, the burning rate in the compartment is normally limited by the amount of oxygen available in the air for combustion. Flames may emerge from any opening. Un-burnt fuel in the smoke may burn as it meets the fresh air in the adjacent compartments. Structural damage to exposed steel normally occurs as it is heated to extreme temperatures. A fully developed fire will normally be inaccessible by hose teams and require extinguishment by indirect attack. A compartment can reach the fully developed fire stage very quickly in machinery space, flammable liquid fires or enemy weapon induced fires. Decay Stage 0143. Eventually, the fire consumes all available fuel, at which time combustion slows down (decays) and the fire goes out. RESTRICTED 1-12  RESTRICTED INBR 1835 (I) Effect of Fire in a Compartment 0144. The effect of fire spread through metal boundaries on heat tolerance, Ignition Times, Radiant Heat vs Time and temperature vs Time is depicted in Fig 1.4 to 1.7 respectively. 20 MIN DEATH 10 MIN UNCONSCIOUS 7 MIN INCAPICITATION 5 MIN POST FLASHOVER FULLY DEVELOPED FIRE 10 MINS- FAULT 1830 °F + (1000 °C+) ADJACENT SPACE Fig 1.2: Fire Spread Through Metal Boundaries- Ignition Times METAL BULKHEADS AND DECKS 5 MINS- OK FIRE SPACE Fig 1.4: Fire Spread through Metal Boundaries- Heat Tolerance RESTRICTED 1-13  RESTRICTED INBR 1835 (I) CABLES COMPARTMENT ABOVE ADJACENT OMPARTMENT IGNITION TIMES IGNITION TIMES PAPER ON CABINET PAPER ON DECK- 3-4 MIN PAPER 1’ FRM BHD- 20 MIN PAPER 1’ ABOVE- 5 MIN PAPER AGAINST BHD- 7 MIN PAPER ON CABINET-15 MIN PAPER 1’ ABOVE DECK CABLE S 1’ FROM BHD- 40 MIN CABLES AT CEILING-25 MIN PAPER AT CEILING- NO IGNITION PAPER ON DECK ADJACENT SPACE NO IGNITION POST FLASHOVER CABLES 1’ FROM FULLY DEVELOPED FIRE BULKHEAD 1830 °F + (1000 °C+) METAL BULKHEADS AND DECKS PAPER AGAINST BH PAPER 1’ FROM BH Fig 1.5: Fire Spread Through Metal Boundaries- Ignition Times RESTRICTED 1-14  RESTRICTED INBR 1835 (I) RADIANT HEAT 1’ ABOVE DECK 5 MIN- 20 KW/M2 10 MIN- 50 KW/M2 20 MIN- 75 KW/M2 RADIANT HEAT 1’ FROM ADJACENT SPACE BULKHEAD POST FLASHOVER FULLY DEVELOPED FIRE 1830 °F + (1000 °C+) METAL BULKHEADS AND DECKS FIRE SPACE 5 MIN- 2.7 KW/M2 10 MIN- 9.8 KW/M2 20 MIN- 21 KW/M2 Fig 1.6: Fire Spread Through Metal Boundaries- Radiant Heat vs Time RESTRICTED 1-15  RESTRICTED INBR 1835 (I) AIR TEMPERATURE 5 MIN- 190°F (88°C) 10 MIN- 390°F (199°C) 20 MIN-611°F (322°C) DECK TEMPERATURE 5 MIN- 890°F (477°C) 10 MIN- 1285°F (696°C) 20 MIN-1515°F (824°C) AIR TEMPERATURE ADJACENT SPACE 5 MIN- 86°F (30°C) POST FLASHOVER 10 MIN- 118°F (48°C) FULLY DEVELOPED FIRE 1830 °F + (1000 °C+) 20 MIN- 180°F (82°C) METAL BULKHEADS AND DECKS FIRE SPACE BULKHEAD TEMPERATURE 5 MIN- 394°F (201°C) 10 MIN- 714°F (379°C) 20 MIN- 972°F (522°C) Fig 1.7: Fire Spread Through Metal Boundaries- Temperature vs Time RESTRICTED 1-16  RESTRICTED INBR 1835 (I) CHAPTER 2 THEORY OF FIRE EXTINGUISHER CONTENTS TOPICS ARTICLE NO. Principles of Fire Extinguishing 0201 Cooling 0202-0203 Smothering 0204-0205 Starving 0206-0207 Free Radical Quenching 0208 Effective Extinguishing Media for Different Class of Fire 0209-0210 Water as an Extinguishing Agent 0214-0222 Water Reactive Metals 0223 Foam Extinguishing Agents 0225-0228 Extinguishing Features of Foam 0229-0232 Types of Foam 0233 Aqueous Film Forming Foam 0234-0236 High Expansion Foam Compound 0237-0239 Fluoroprotein Foam Compound 0240-0241 Film Forming Fluoroprotein Agents (FFFP) 0242 Protein Foam Compound 0243-0244 Alcohol /Polar Solvent Resistant Foam 0245-0246 Chemical Foam Agents 0247 Comparison of Various Foams 0248-0249 Carbon Dioxide as an Extinguishing Agent 0251-0253 Dry Chemical as an Extinguishing Agent 0255-0265 Halon as an Extinguishing Agent 0267-0272 Halon –Substitutes and Alternatives 0273-0277 Chemical Substitutes for Halon 0278-0284 Non –Chemical Substitutes for Halon 0285-0289 Comparison of Halon Alternatives 0290 Extinguishing Agents for Metal Fire 0293-02105 RESTRICTED 2-1  RESTRICTED INBR 1835 (I) CHAPTER 2 THEORY OF FIRE EXTINGUISHMENT Principles of Fire Extinguishing 0201. Fire safety, at its most basic, is based upon the principle of keeping fuel sources and ignition sources separate. Fire extinction, in principle, consists in breaking any one arm of the Fire Tetrahedron. Methods of extinguishing fire may therefore be classified as Cooling, Smothering, Starving and Free Radical Quenching. In practice, specific methods of fire extinction often embody more than one of these principles. Cooling 0202. Cooling is the process of reducing temperature of the combustible substance (Fig 2.1), to a point, where combustible vapours are no longer evolved or where activation energy is lowered to the extent that no activated atoms or free radicals are produced. This is usually been done by the use of water. The extinguishing medium operates by absorbing heat from the fire, as a consequence of which it may undergo one or more of the following changes :- (a) Its temperature is raised; (b) It is converted to the vapour state; (c) It is decomposed; (d) It reacts chemically with the burning material. FREE RADICALS OXYGEN FUEL COOLING Fig 2.1: Cooling – Removal of Heat 0203. In applying the principle of fire extinction, the first step is to accelerate the speed with which the heat is removed from the fire. This reduces the temperature of the burning mass and consequently reduces the rate at which heat is produced. In due course the rate at which the heat is lost from the fire exceeds the rate of heat production and the fire dies away. The application of a jet or spray of water to a fire is invariably based on this simple but fundamental principle. Another example is the emulsification of the surface of oil, by means of the emulsifying type of sprinkler head, producing an oil-in-water emulsion. RESTRICTED 2-2  RESTRICTED INBR 1835 (I) Smothering 0204. Smothering is the process of removal or dilution of oxygen (air) (Fig 2.2) to a point where combustion ceases. The concentration of oxygen is reduced to below the minimum 16% oxygen required for combustion to sustain. This is achieved usually by using CO2, steam or foam. Small fires, such as those involving a person's clothing, can be smothered with a rug, blankets etc, while the sand or earth can be used on a small metal fire. FREE RADICALS OXYGEN FUEL COOLING Fig 2.2: Smothering – Removal of Oxygen 0205. Foam forms a viscous coating over the burning material and limits the supply of air, when it covers the burning material completely. It also tends to prevent the formation of flammable vapour. Another method of smothering, is by the application of a cloud of finely divided particles of dry powder, usually sodium bicarbonate. A further development is the use of a powdered compound for use on metal fires, such as uranium and plutonium, thorium and magnesium. The vigorous discharge of an inert gas in the vicinity of the fire, reduces the oxygen content of the atmosphere for the time being, so that combustion cannot be maintained. Starving 0206. Physically separating/ removing the combustible material from the neighbourhood of the fire, or sub-dividing the burning material, to a point where there is nothing remaining to oxidize (Fig 2.3). FREE RADICALS OXYGEN FUEL COOLING Fig 2.3: Starving - Removal of Fuel 0207. The extinction of fire by starvation is undertaken in three ways: (a) By removing combustible substance material from the neighbourhood of the fire. Eg, drainage of fuel from burning oil tanks, the removal of cargo from a ship fire, etc. RESTRICTED 2-3  RESTRICTED INBR 1835 (I) (b) By removing the material on fire from the other combustible material present in the vicinity eg, pulling apart a burning haystack or a thatched roof. (c) By sub-dividing the burning material, when the smaller fires produced may be left to burn out or to be extinguished more easily by other means. Eg, the emulsification of the surface of the burning oil, etc Free Radical Quenching. 0208. Interruption of flame chemistry of the chain reaction of combustion, by the injection of compounds capable of quenching free radicals, is called as Free Radical Quenching (Fig 2.4). FREE RADICALS OXYGEN FUEL COOLING Fig 2.4: Free Radical Quenching – Removal of Free Radicals Effective Extinguishing Media for Different Class of Fires. 0209. The extinguishing media for different class of fires are given in Table 2.1. Class of Extinguishers Fire A Pressurised water, Dry Chemical, Ammonium Phosphate B Carbon dioxide, expelled as a gas or Dry Chemical, Ammonium phosphate or Dry chemical, sodium bicarbonate and potassium bicarbonate, urea-based potassium preferred for extinguishing cooking oil fires or Halon expelled as a gas or Water spray, foam, light water, vapourising liquids C Foam or Dry Chemical Powder, Ammonium phosphate. Water in the form of spray is generally used to cool the containers. Halon can also be used D Powdered graphite, powdered talc, soda ash, limestone and dry sand E Carbon dioxide, expelled as a gas or Dry Chemical, Ammonium phosphate or Dry chemical, sodium bicarbonate and potassium bicarbonate, urea-based potassium or Halon expelled as a gas Table 2.1: Extinguishing Media for Different Classes of Fire 0210. Extinguishers for Class D fires are specially formulated to treat organic and alkali metals that cannot be safely extinguished by other fire extinguisher agents. Extinguisher for Class D fires is not to be used for extinguishing Class A, B, or C fires. Class D fires are caused by ignition of organic RESTRICTED 2-4  RESTRICTED INBR 1835 (I) metals such as lithium (an alkali metal), aluminum, or sodium. Class D fires are particularly troublesome to extinguish because of the intensity with which they burn and their ability to react chemically with normal extinguishing agents. Eg, carbon dioxide will not react with cold sodium but accelerates the burning rate of ignited sodium. The two agents that are used to extinguish Class D fires, are sand and sodium chloride. To extinguish Class D fires, water, foam, carbon dioxide are used. Halons , graphite, soda ash, or powdered sodium chloride are used for extinguishing fires involving alkali metals. The extinguishing agent has to be dry as moisture can react with the metal. 0211 - 0213. Spare EXTINGUISHING MEDIA - PROPERTIES Water as an Extinguishing Agent 0214. A great majority of fires are extinguished by use of water from a hose delivering a solid stream or a spray; from a sprinkler system or a water spray system; or from a pump, tank or bucket. The physical properties that make water a good extinguishing agent are :- (a) At ordinary temperature water is a heavy, relatively stable liquid. (b) When water is converted from liquid to vapour, its volume at atmospheric pressure increases about 1600 times. This large volume of water (saturated steam) displaces an equal volume of air surrounding a fire, thus reducing the volume of air (oxygen) available to sustain combustion. (c) High specific heat capacity of water (4.186 KJ/Kg K). (d) High latent heat of vaporization of water (530 K Cal/ mole), causes rapid cooling. 0215. Water based extinguishers are effective against burning paper, cotton and wood fibres, and paper trash. Water's ability to extinguish Class A fires rests on its ability to cool the fuel and exclude oxygen. More specifically, water excludes or dilutes oxygen, by the formation of steam. Its high heat capacity accounts for its cooling ability. Water is not to be used on Class B, C, D or E fires, because it can worsen the fire or accelerate the conditions causing the fire. Water worsens Class B fires because most fuels have a density less than that of water. The fuel will float on top of the water and spread as the water flows to the lower levels. While floating on the water's surface, the fuel's oxygen supply is not disturbed nor is the fuel cooled. Water cannot be used on Class D fires because of the chemical reactions, especially oxidation, which can occur between water and the metal. One is at risk of electric shock if water is used on live electrical equipment. Cooling Action of Water 0216. Surface cooling is not usually effective on gaseous products and flammable liquids that have flash points below the temperature of the applied water. Water is generally not recommended for flammable liquids with a flash point below 100 deg F (37.8 deg C). Water spray cools a fire according to the following principles :- RESTRICTED 2-5  RESTRICTED INBR 1835 (I) (a) The rate of heat transfer is proportional to the exposed surface of the liquid. For a given quantity of water the surface is greatly increased by conversion to droplets. (b) The rate of heat transfer depends on the temperature difference between the water and the surrounding air or burning material. (c) The rate of heat transfer also depends on the vapour content of the air. (d) The heat absorbing capacity of water depends upon the distance it travelled and its velocity near the fire (heat source) and fire plume. 0217. When the heat absorption rate of the water spray approaches the total heat release rate of the fire, fire control begins. Wetting combustible materials is a method often employed to prevent ignition of unburned materials. If combustibles absorb water, it takes longer to ignite them because the water must be evaporated before the materials can get hot enough to burn. Smothering Action of Water 0218. If enough steam is generated, air can be displaced or excluded. Fires in certain materials can be extinguished by this smothering action, which is speedier if the steam generated can be confined to the combustion zone. Water might be used to smother a burning flammable liquid when the liquid has a flash point above 100 degrees Fahrenheit, a specific gravity of 1.1 or heavier, and is not water- soluble. To achieve smothering most effectively, a foaming agent normally is added to the water. The water then must be applied gently to the surface of the liquid. In cases where oxygen is produced while a burning material decomposes, smothering by any agent is not possible. Emulsification Action of Water 0219. An emulsion is formed when immiscible liquids incapable of blending or mixing are agitated together and one of the liquids is dispersed throughout the other. Extinguishment through emulsification can be achieved by applying water to certain viscous flammable liquids, which then cools the surfaces of such liquids and prevents the release of flammable vapours. A relatively strong coarse water spray normally is used for emulsification. Solid stream of water is to be avoided, as it will cause violent frothing. Dilution Action of Water 0220. Fires in water-soluble, flammable materials may, in some instances, be extinguished by dilution. Eg, dilution can be used successfully in a fire involving an ethyl or methyl alcohol spill, if it is possible to get an adequate mixture of water and alcohol. 0221. Other advantages of water as an extinguishing agent are: (a) Cheaply available. (b) No requirement of storage. (c) Can be transported anywhere within the ship in pipelines without any hazards. RESTRICTED 2-6  RESTRICTED INBR 1835 (I) (d) No danger to human on use, so no requirement of evacuation of compartment. (e) Water jet displaces most of the combustible substances. (f) High surface tension and thus can be spread in consolidated streams. 0222. Some of the disadvantages of water as an extinguishing agent are :- (a) Limited use in climates where freezing temperatures are encountered, because water freezes at 32 deg F (0 deg C). (b) The relatively high surface tension of plain water shows its ability to penetrate burning combustibles, and impedes its spread throughout any closely packed, or stacked materials. (c) Water tends to run off surfaces quickly due to the relatively low viscosity and limits its ability to blanket a fire by forming a barrier on the surface of combustible materials. (d) Friction losses in fire hoses. (e) In its natural form it is a good conductor of electricity and can cause an electric shock to the user. (f) High density can cause stability problems onboard ship. (g) Sea water is corrosive in nature, and can damage most of the equipments. (h) Cannot be used to extinguish oil, metal and electrical fires. Water Reactive Metals 0223. The temperature of metal (Magnesium, Aluminium, Sodium, Potassium) fires is very high and if water is used it will produce hydrogen gas, which is highly inflammable can cause a violent explosion. Therefore water cannot be used on metal fires. 0224. Spare Foam Extinguishing Agents 0225. Fire fighting foam is an aggregate of gas filled bubbles made from aqueous solutions of a specially formulated concentration of liquid foaming agents. The gas used is normally air, but in certain applications can be an inert gas. Since foam is lighter than flammable liquids, it floats on all flammable or combustible liquids. This produces air-excluding, cooling, continuous layer of vapour- sealing, water-bearing material that halts or prevents combustion. Foam is produced by mixing a foam concentrate with water in an appropriate quantity, and then aerating and agitating the solution to form the bubble structure. RESTRICTED 2-7  RESTRICTED INBR 1835 (I) 0226. Some foams are thick and viscous and form tough, heat resistant blankets over burning liquid surfaces and vertical areas; other foams are thinner and spread more rapidly. High proportioning may cause foam to be stiff and the concentrate will be wasted, while low proportioning might make foam weak and unstable. 0227. Foam is unstable and may be broken down easily by a physical or mechanical force, such as a water hose stream. Certain chemical vapours or fluids may also destroy foam quickly. Foam solutions are conductive and therefore not recommended for use on electrical fires. 0228. Foam liquid should generate sufficient volume of foam to produce adequate blanketing effect. The expansion capacity depends upon capacity to incorporate air in thin liquid film. This property is achieved by addition of suitable hydrocarbon surfactants alone or in combination. The foam produced should be stable; the liquid should drain out after sufficient time to bring about the cooling and blanketing effect. According to the expansion ratio, (the ratio of final foam volume to original foam solution volume before adding air), the foams are subdivided into three categories: (a) Low expansion foam -- expansion up to 20:1 (b) Medium expansion foam -- expansion up to 20 to 200:1 (c) High expansion foam -- expansion up to 200 to 1000:1 Extinguishing Features of Foam 0229. Low expansion foam is used principally to extinguish burning flammable or combustible liquid spills or tank fires by application to develop a cooling, coherent blanket. Foam is the only permanent extinguishing agent used for fires of this type. A foam blanket covering a tank's liquid surface can prevent vapour transmission for some time, depending on stability and depth of the foam. Fuel spills are rendered safe by foam blanketing. Foams can be used to diminish or halt the generation of flammable vapours from non-burning liquids or solids, and to fill cavities or enclosures where toxic or flammable gases might collect. Sudden large fuel spills resulting from aircraft accidents or malfunctions require rapid foam application. Hangar fire protection is best accomplished by foam -water sprinkler systems and portable foam equipment. 0230. Foams of the medium or high expansion type might be used where fires are difficult or impossible to reach. These are agents for control and extinguishment of class 'A' and 'B' fires, and are particularly suited as a flooding agent for use in confined spaces. The foam is an aggression of bubbles, mechanically generated by aspiration or a blower-fan. Their water content also cools and diminishes oxygen by steam displacement. Foams of this type may be used to control liquefied natural gas spill fires and help to disperse the resulting vapour cloud. 0231. Many foams are generated from solutions with very low surface tension and penetration characteristics. Foam breaks down and vaporizes its water content under attack by heat and flame. It therefore must be applied to a burning liquid surface in sufficient volume and rate to compensate for this loss, with an additional amount applied to guarantee a residual foam layer over the extinguished RESTRICTED 2-8  RESTRICTED INBR 1835 (I) liquid. Foam therefore should have good resistance to heat. This is achieved by incorporating the following surface-active agents: - (a) Fluoro Surfactant. They reduce surface tension of water even at very low concentrations. They form a polymeric film on the fuel surface when the liquid is drained from foam bubbles, which is thin yet strong and prevents the fuel vapours from escaping into the surroundings. (b) Anionic Surfactants. They give additional expansion capacity and provide stability to the foam bubbles. (c) Non Ionics. The stability and the heat resistance of the foam produced by anionic surfactants are improved by incorporating suitable non-ionic surfactants. 0232. Foam works in the following way to extinguish a fire: - (a) Produces a blanket, which isolates fuel from air. (b) Suppresses flammable vapours of the fuel and prevents their release to the atmosphere. (c) Separates flame from fuel surface. (d) Water released from foam absorbs the heat thereby cooling the fuel surface. Types of Foam 0233. The types of foam used for fire extinguishing are: (a) Aqueous Film-Forming Foam Agents (AFFF). (b) Fluoroprotein Foaming Agents (FP). (c) Film-Forming Fluoroprotein Agents (FFFP). (d) Protein Foaming Agents (PF). (e) Alcohol Resistant Foam/ Alcohol Type Concentrate (ATC) (f) High Expansion Foam (HIEX) Compound Aqueous Film Forming Foam (AFFF) 0234. Aqueous Film Forming Foam (AFFF) is a synthetic foam containing fluorocarbons, hydrocarbon surfactants, stabilizers and anti freezing agents. They form air-foams similar to those produced by the protein-based materials. In addition, these foaming agents are capable of forming water solution films on the surface of flammable hydrocarbon liquids. The air foams generated from RESTRICTED 2-9  RESTRICTED INBR 1835 (I) AFFF solutions possess low viscosity, have fast spreading and levelling characteristics and like other foams, act as surface barriers to exclude air and halt fuel vaporisation. These foams also develop a continuous aqueous layer of solution under the foam, maintaining a floating film (of thickness 0.0127 mm) on hydrocarbon fuel surfaces to help suppress combustible vapours and cool the fuel substrate. 0235. AFFF fluidity and film strength on a layer of kerosene makes it particularly suitable for jet aircraft fuel spill fire fighting. It is used 3-6% by volume with water, is non-toxic and biodegradable after dilution. Time required for complete extinguishment of fire is about 90 seconds. This foam can extinguish a flammable liquid fire in less time than conventional foams with minimal chances of reignition. More importantly, an aqueous solution drains from the foam bubbles and forms a vapour sealing film, which floats on the fuel surface. This film is tough, persistent and suppresses formation of volatile vapours. In addition, it has a reforming, self-sealing action, which prevents re-flash, should the foam be disturbed. Quality 'AFFF' nullifies the fire hazard out of fuel spills because it seals and secures non-ignited areas and prevents ignition. It is compatible with all known protein and synthetic foams as well as with foam compatible dry powders. 0236. The ability to form a vapour seal over flammable liquids permits AFFF to extend its performance well beyond that of ordinary foams. This performance is important in a situation where access is limited. The vapour sealing film flows with the fuel and secures as it goes. It can be used either with fresh, brackish or seawater. AFFF concentrate is available for use at 6%, 3% and 1% concentrations, with an expansion factor greater than 6, and can be used with all conventional foam equipments. In addition, its unique properties make it suitable for use in water fog / spray nozzle and monitors, deluge sprinklers and spray systems, closed head sprinklers, sub surface injection (Storage tanks) and hose reel installation. Existing vehicles and systems can be simply converted or refitted to take advantage of the unique AFFF benefits. It is used as a first aid agent in high risk situations such as aircraft crash fires, where quick fire attack and control are essential to protect life or to prevent ignition of a larger fire. High Expansion Foam (HIEX) Compound 0237. High Expansion Foam compound (HIEX) is a special composition of surfactants solubilisers, stabilizers and antifreeze agent designed to produce foam with low drainage time, superior fluidity and fire resistance. Suitable for use with low, medium and high expansion foam equipment for rapid blanketing of large surfaces or total flooding of enclosed volumes. Use with either fresh water or sea water at concentration between 1% and 3% can produce a very stable foam for indoor class A fires involving paper products, plastics and rubber. 0238. 'HIEX' liquid with medium expansion foam making equipment may be used for the control of cryogenic flammable liquid fires (B Class) and for the suppression of vapour release from toxic liquid spillage and offers advantages over low expansion foams for these risks. When used with High Expansion Foam Generator, it produces three dimensional foam which is suitable for fires in high volume areas such as engine or boiler room, aircraft hangers, turbine peaking units, railroad accidents and other inaccessible places, where the application of conventional fire fighting agents is more difficult and where damage must be kept to a minimum. RESTRICTED 2-10  RESTRICTED INBR 1835 (I) 0239. HIEX Foam controls Class ‘A` fires by oxygen exclusion and limiting heat radiation. Effective smoke and heat barriers are quickly created permitting other fire fighting equipment to tackle the seat of the fire. Class B fire fighting is efficient since HIEX foam very quickly covers flammable liquid surface without splashing and helps to cut off flammable vapour release. Its features are: (a) Excellent cooling capacity of surfaces. (b) Easy filling of volumes of any dimension and size. (c) Long Life over wide temperature range. (d) Non-toxic, non-corrosive and easily biodegradable. (e) Compatible with all foams produced with a synthetic or protein base, as well as with all suitable extinguishing powders. Fluoroprotein Foam Compound 0240. The Fluoroprotein foam compound is composed of a combination of selected fluorotensides with a protein base. The concentrates utilised for generating fluoroprotein foams are similar in composition to protein foam concentrates, but, in addition to protein polymers they contain fluorinated surface active agents that confer a "fuel shredding" property to the foam generated. This makes them particularly effective for in-depth crude petroleum or other hydrocarbon fuel fires. Hence fluoroprotein foam is a right choice for storage tank farms protection, oil jetties, refineries and offshore oil platforms. 0241. In addition, these foams demonstrate better compatibility with dry chemical agents than do the regular protein type foams. They have increased extinguishment ability, enhanced fluidity, assure better burn back resistance, sealability, resists hydrocarbon saturation, and are non-toxic and biodegradable after dilution. Recommended rate of application for hydrocarbon fires is 2 - 5 L / Sq. Mtr. To obtain optimum foaming it is recommended that induction of foam compound is 3-4%. For long throw equipment and for adhesive foam, a higher rate of 5-6 % foam induction is recommended. Depending on type of equipment, water pressure and induction, the expansion factor varies from 6 to 10. It is compatible, for use in emergency, with other equivalent ISI marked Fluoroprotein / Protein base foam compound, but they must not be mixed together in storage containers. Film Forming Fluoroprotein Agents (FFFP) 0242. Film Forming Fluoroprotein Agents (FFFP) are composed of protein together with film- forming fluorinated surface-active agents, which make them capable of forming water solution films on the surface of most flammable hydrocarbons and of conferring fuel shredding property to the foam generated. Air foams generated from FFFP solutions have fast spreading and levelling characteristics and, just as other foams, act as surface barriers to exclude air and prevent vaporization. Like AFFF, they generate a self-healing, continuous floating film on hydrocarbon fuel RESTRICTED 2-11  RESTRICTED INBR 1835 (I) surfaces, which helps suppress combustible vapours. FFFP concentrates are available for proportioning to a final concentration of either 3% or 6% by volume, using either fresh water or sea water. Protein Foam Compound 0243. The Protein foam compound is prepared from hydrolyzed animal and vegetable proteins with additives to improve thermal stability, storage and cohesion. Protein-type air-foams utilize liquid concentrates proportioned with water for their generation. It is used to produce low expansion foam and is reliable agent for protection of hazards involving non-polar flammable liquids. Protein foam produces a stable foam which flows over burning surfaces forming a cohesive continuous air- excluding, cooling blanket. Its water content also provides cooling of fuel and surfaces such as hot metal of tank shells. 0244. These concentrates produce dense, viscous foams of high stability, high heat resistance and good resistance to burn back, but they are less resistant to breakdown by fuel saturation than are AFFF and fluoroprotein foams. They are non-toxic and biodegradable after dilution. The recommended rate of application is 2.5 to 8 lpm/m2 by projecting or spraying, and the time required for complete extinguishment of fire is 180 seconds. To obtain optimum foaming, it is recommended that an induction of foam compound is 3 to 4 %. For long throw equipment and for adhesive foam, higher 5-6% foam induction is recommended. Depending on type of equipment, water pressure and induction, the expansion rate varies from 6 to 10. Alcohol / Polar Solvent Resistant Foam 0245. Polysaccharide is added to AFFF formulation, with surface-active substances and polymer additives. The polysaccharide forms a strong film on the surface of polar fuel which provides blanketing effect and prevents the release of vapour into the atmosphere. Alcohol resistant foam compound is used for rapid action on surface fires. It produces a foam carpet having good resistance to contamination of hydrocarbons and dehydration of polar solvents. It is to be used in 3% concentration on hydrocarbons and at 6% concentration on polar solvents. They suppress fires in Class A materials more effectively than plain water. 0246. Polar Solvent, Resistant Foam on Water Soluble Flammable Liquids form a cohesive thin polymeric layer at the interface between foam and fuel. If the protective layer should become disrupted by agitation, more of the polymeric layer is produced by means of regeneration action (known as self-handling). This unique action enables the foam to extinguish and secure effectively, thus providing burn back protection far greater than conventional non AFFF agents. Chemical Foam Agents 0247. Chemical foam agents have become obsolete because of the superior economics and ease of handling of the liquid foam-forming concentrates. Chemical foam is formed from the chemical reaction in aqueous solution between aluminium sulphate and sodium bicarbonate, which also contains proteinaceous foam stabilizers. Foam is generated by the generation of carbon dioxide gas trapped in the bubbles of the foaming solution. RESTRICTED 2-12  RESTRICTED INBR 1835 (I) Comparison of Various Foams 0248. Comparison of properties of various foam agents is as as given in Table 2.2: - Property AFFF ATC PF FP FFFP Speed of spreading Excellent Poor Poor Good Good Burn back resistance & Fair Excellent Excellent Excellent Excellent Re-ignition resistance (12 min) Fuel tolerance Fair Excellent Fair Good Good Shelf life Very Good (10 yrs) Good Poor (2 yrs) Poor Good Table 2.2: Properties of Various Foaming Agents 0249. Application guidelines for various foams are as given in Table 2.3:- Application AFFF ATC PF FP FFFP Hydrocarbon Yes Yes Yes Yes Yes Polar Solvent No Yes No No No Airport Yes No No Yes Yes Marine Yes No No Yes No Refineries No Yes No Yes No Oil & Gas Yes No No No Yes Class A (Forest) Yes Yes Yes Yes Yes LPG/ LNG Yes Yes Yes Yes Yes Table 2.3: Application Guidelines for Various Foams 0250. Spare Carbon Dioxide as an Extinguishing Agent 0251. Carbon dioxide reduces the oxygen content of the atmosphere by dilution to a point where the atmosphere no longer will support combustion (12-15 % down from normal 21 %). Thus, fire is extinguished by smothering. Being heavier than oxygen, it settles on the fuel surface and produces the required blanketing effect. It extinguishes Class B and C fires by depleting oxygen and cooling the fuel. The use of carbon dioxide on general Class A fires is limited mostly by its low cooling capacity and enclosures incapable of retaining an extinguishing atmosphere. It is used in the extinguishment of flammable liquid fires, gas fires, fires involving electrically energized equipment, delicate instruments, optical systems and to a lesser extent in fires in ordinary combustibles such as paper, cloth, and other cellulose materials. Carbon dioxide extinguishers are not to be used against fires caused by lithium aluminium hydride. 0252. Carbon dioxide has a number of properties that make it a desirable fire extinguishing agent. The advantages of using it as an extinguishing agent are: (a) Non-combustible, clean gas which leaves no residue on use. RESTRICTED 2-13  RESTRICTED INBR 1835 (I) (b) Does not react with most substances. (c) Provides its own pressure for discharge from the storage container. It is stored in banks of high cylinder pressure of 5.9 Mpa (d) Can penetrate and spread to all parts of the fire area. (e) It is nonconductive and therefore safe to use on electrical fires. (f) Mildly toxic. But all traces can be removed after thorough ventilation. (g) It has zero ozone depletion potential (ODP) and zero atmospheric life time. (h) Large volumes may be liquefied and maintained in a small container at normal temperature and at not extremely high pressures (850 psi at 15 deg C). (j) Can be used on flammable liquid fires, gas fires, electrical fires and to a lesser extent on solid fires. (k) It is cheap and readily available. (l) It is effective in smothering and cooling burning liquids such as hydrocarbons. 0253. Some of the disadvantages of using carbon dioxide as an extinguishing agent are: (a) It can cause unconsciousness and death when present in fire extinguishing concentrations. The lethal percentage is 16 %. These reactions are due more to suffocation than to any toxic effect of CO2 itself. Therefore, it is not suitable for protection of occupied spaces. (b) It is a greenhouse gas and contributes to global warming. (c) It has a low efficiency in extinguishing fires, because of the high concentrations required. Therefore greater number of cylinders will be required. Space required for the storage of these cylinders is a problem. (d) It has insignificant Cooling Effect, since dry ice (another name for CO2) does not wet the surface to be cooled. (e) Cannot be used on certain metal fires, since it gets decomposed. (f) It has a short target range. (g) It is an asphyxiate (It causes suffocation). (j) It is delivered at an extremely low temperature and can cause thermal shock and create hairline cracks in circuit boards. RESTRICTED 2-14  RESTRICTED INBR 1835 (I) (k) It can cause frostbite on contact with the skin. 0254. Spare Dry Chemical as an Extinguishing Agent 0255. Dry Chemical agents are mixtures of powdered chemical compounds of varying composition used as fire extinguishing agents. Borax and Sodium Bicarbonate based dry chemicals were the first agents developed. The terms "Regular Dry Chemical" generally refer to powders, that are listed for use on Class B and Class C fires. "Multipurpose Dry Chemical” refers to powders listed for use on Class A, B, and C fires. The chief base chemicals used in the production of currently available dry chemical extinguishing agents are Sodium bicarbonate, Potassium Bicarbonate, Urea-Potassium Bicarbonate, Mono-Ammonium Phosphate and Ternary Eutectic Chloride. Various additives are mixed with these base chemicals to improve their storage, flow, and water-repellence characteristics. The most commonly used additives are metallic stearates, Tri-Calcium Phosphate or Silicones, which coat the particles of dry chemical to make them free flowing and resistant to the caking effects of moisture and vibration. Dry Chemical Powder Quality - BC &E Type 0256. The composition of this powder is Sodium Bi Carbonate, Potassium Bi-Carbonate and Potassium Sulphate. All the powders are coated with high grade Silicone hydro-phobien agents. It is a fine easily free flowing powder, suitable for extinguishing flammable liquids (petroleum oil, alcohols, etc.), gases burning under pressure (Methane, Propane, etc.), Plastics, Polyethylene, Polyurethane, Polysterol, etc and on fire in dry electrical installations. The extinguishing action is mainly due to the anti-catalytic action caused by breaking the radical chains present in the flame. It is suitable for hand operated fire extinguishers of all types as well as for mobile extinguishers and fixed installations. Dry propelling agents, such as compressed air, Nitrogen and Carbon dioxide, can be used. All powders are fully foam compatible and contain no constituents, which could cause toxic damage to humans or animals. They can be packed in 5 Kg / 10 Kg / 50 Kgs Polyethylene lined HDPE Bags or Plastic/ Fibre drums with inner Polyethylene bags of 50 Kgs. All B, C powders display outstanding properties when transported through pipes, hoses, etc. under pressure. In a dry state, they do not have corrosive effect on metals. Dry Chemical Powder Quality - D Type 0257. The composition of this powder is based on Ternary Eutectic Chloride with the addition of high melting compounds. On the fires involving metals, the extinguishent need to be applied gently. This special technique is achieved by applying the extinguishent via an applicator, which is screwed on to a dry chemical nozzle. Powder blanket adheres immediately and remains impermeable to air. A dense crust is formed through the influence of the high temperature. Quality D is a special dry chemical powder for metal fires such as Sodium, Potassium, Calcium, Aluminium, Titanium, Zirconium and various alloys. Quality D is a fine grey, easily flowing powder. It contains no toxic constituents and neither are any toxic products of decomposition given off in a fire. The powder can be stored safely without affecting its efficiency for at least 2 years if kept in its original packages, which are hermetically sealed plastic polythene lined of 25 / 50 Kg net capacity containers. RESTRICTED 2-15  RESTRICTED INBR 1835 (I) Dry Chemical Powder Quality - B and C 0258. It is manufactured with a base of a mixture of Ammonium Phosphates and Ammonium Sulphate. It is suitable for extinguishing smouldering fires (wood, textiles, rubber tyres etc.), flammable liquid fires (Petroleum, gasoline, oil etc.), gases burning under pressure (methane, propane and domestic gas) and, for fires in dry electrical installations and also for fires in light metals. It is suitable for hand operated fire extinguishers of all types, as well as for mobile extinguishers and fixed installations. Dry propelling agents such as compressed air, nitrogen, and carbon dioxide can be used. It is non-corrosive and non-abrasive. Dry Chemical Mono-Ammonium Phosphate (MAP) 0259. This agent can be used for Class A, B, C and E fires, but is not to be used on organic metal (Class D) fires. The MAP agents has the same advantage as carbon dioxide, in that they smother the fire and choke off the oxygen supply. This advantage makes the MAP ideal for use on virtually any material except organic metals. However effective, the MAP has the disadvantage of leaving a sticky residue or powder, which is especially troublesome in electronic equipment. It also has no cooling effect on the fuel or other heated equipment. An additional coolant is sometimes needed to prevent flare-up. Dry Chemical Potassium or Sodium Carbonate Agents 0260. These are effective against burning grease and oil. These dry chemical agents are like MAP agents except, that they contain either potassium or sodium carbonate as the extinguishing agent. They can be used on Class B, C and E fires, but not on Class A and Class D fires. These agents smother burning grease much faster and more certainly, than the MAP agents. The Potassium or Sodium Bicarbonate interferes with the clumping of fats and oils. One major disadvantage of these agents, is the sticky residue, which, like the MAP agents, presents the same problems when used on electrical equipment. These agents also require additional coolant. Smothering Action of Dry Chemical 0261. When multipurpose dry chemical is discharged into burning ordinary combustibles, the decomposed Mono-Ammonium Phosphate (NH4 H2 PO4) leaves a sticky residue (Meta-Phosphoric Acid, HPO3) on the burning material. The residue (powder dust cloud) seals glowing material from oxygen, thus helping to extinguish the fire and prevent re-ignition. The chemical reaction is: NH4 H2 PO4 + Heat (350 deg C) = NH3 + H3 PO4 NH3 + H = NH4 NH4 + OH = NH3 + H2O H3 PO4 = H2O + HPO3 Cooling Action of Dry Chemical RESTRICTED 2-16  RESTRICTED INBR 1835 (I) 0262. Dry chemical absorbs heat to become chemically active thereby providing cooling. Discharge of dry chemical produces a cloud of powder between the flame and the fuel. This cloud shields the fuel from some of the heat radiated by the flame thereby providing a cooling action. Chain-Breaking Reaction by Dry Chemical 0263.. The carbonates, bicarbonates and phosphate of alkali and alkaline earth metals decompose at relatively low temperature and consume free radicals thereby reducing fire intensity. Discharge of dry chemicals into the flames prevents reactive particles from coming together and continuing the combustion chain reaction. An example of reaction of Sodium bicarbonate is: 2 Na H CO 3 + Heat = CO2 + H2O + Na2 CO3 Na2CO3 + Heat = CO2 + Na2 O Na2 O + H2O (in flame matrix)= 2 Na OH Na OH + H (active in flame) = Na + H2O (inert) Na OH + OH (active in flame) = NaO + H2O (inert) The reactive compounds Na and NaO regenerate NaOH by reaction in the flame matrix. 0264. The Dry Chemical Agent should have the following properties, to be an effective extinguishing agent :- (a) Free Flow Property. This property enables the agent to spread and cover a large area, in shortest possible time. Free flowing characteristics are achieved by controlling the particle size of the powder and treating these particles with a suitable agent. However very fine particles cannot travel a long distance and results in caking during storage. Free flow and water repellence is achieved by siliconising the powder particles. (b) Long Shelf Life. This is achieved either by siliconisation or by adding anti-caking agents. Powder kept in proper condition can have a shelf life of 3 years. (c) Small Rate of Application. It is the critical rate of application of the agent for extinguishing the fire. It depends on the capacity of the chemical compound to quench the Free Radicals. Faster the quenching, lesser the quantity of powder required to extinguish the fire. Smaller particle size helps in coverage of a larger area. Limitations of Dry Chemical Agents 0265. Dry Chemical Agents do not produce a lasting inert atmosphere above the surface of a flammable liquid. Consequently, it’s use will not result in permanent extinguishment of the fire, if there are re-ignition sources present in the compartment, such as hot metal surfaces or persistent electrical arcing. Dry Chemical Agents should not be used in installations where relays and delicate electrical contacts are located (e.g. in telephone exchanges and computer equipment rooms etc), since the insulating properties of dry chemical might render such equipment inoperative. Since few of the dry chemicals are slightly corrosive, they should be removed from all undamaged surfaces as soon as possible after fire extinguishment. The use of water and dry chemical, should be avoided. RESTRICTED 2-17  RESTRICTED INBR 1835 (I) 0266. Spare Halons as an Extinguishing Agent 0267. Halogenated extinguishing agents are hydrocarbons in which one or more hydrogen atoms are replaced by atoms from the halogen series ie, Fluorine, Chlorine, Bromine or Iodine. This substitution results in the non-flammability as well as flame extinguishment properties, to many of the resulting compounds. The Halons are colourless, odourless, non-toxic, liquefied gases which leave no residue. The unique flame-inhibiting property creates an inert, yet survivable atmosphere, in the compartment. Bromine based Halon is much more effective than Chlorine or Fluorine based Halon. Br CF3 + Heat = Br (active) + CF3 (active) CF3 + Heat = F (active) + other CF compounds If Methane (CH4) is the fuel, then Br and F would attack CH4 molecule. CH4 + Br = HBr + other CH compounds CH4 + F = HF + other CH compounds HBr + OH = Br (active) + H2O (inert) HF + OH = F (active) + H2O (inert) 0268. As per the convention, Halon are identified by a 5 digit number. The first digit of the number represents the number of Carbon atoms in the compound molecule; the second digit, the number of Fluorine atoms; the third digit, the number of Chlorine atoms; the fourth digit the number if Bromine atoms; and the fifth digit the number of Iodine atoms. If the fifth digit is zero, it is not expressed. Eg, BromoTriFluoroMethane (BrCF3) is referred to as Halon 1301 (also known as BTM). The presence of Fluorine in Halon 1301 (BromoTriFluoroMethane) increases its inertness and stability, and the presence of other halogen, particularly Bromine, increases the fire extinguishing effectiveness of the compound. The flame extinguishing properties and the toxicity increases from Fluorine to Iodine. 0269. Some of the advantages of Halons are: (a) They are either gases or liquids that rapidly vaporize in fire, and leave no corrosive or abrasive residue. (b) Rapid and complete extinguishment can be achieved with low concentrations, up to 6 %, of agent. (c) High liquid densities permit use of compact storage containers. (d) They can be used at places where damage to equipment or materials or post fire cleanup must be minimized. (e) It is nonconductive and therefore safe to use on live electronic equipment. RESTRICTED 2-18  RESTRICTED INBR 1835 (I) (f) They are primarily used for the protection of electrical and electronic equipment, petroleum production facilities, engine compartments (e.g., those of ships, military vehicles, and aircraft) and other areas where rapid extinguishment is important. (g) Both Halon 1301 and 1211 are at least 2 ½ times more effective than CO2. (h) Halon 1301 can be discharged into occupied spaces. Toxic effects are experienced only above 10% concentration. (j) It leaves no messy residue. (k) It is not a coolant, and thus causes no temperature stress to sensitive electronic equipment. 0270. Some of the disadvantages of Halons are: (a) Halons at high concentrations have toxic and irritant effects on human beings. (b) Halons decompose to toxic substances when exposed to temperatures above 900 degree Fahrenheit. Hence a naked flame should never be brought near a Halon system. (c) Halons (chemically related to chlorofluorocarbons (CFCs) if released in atmosphere depletes the ozone layer and are global warming gases. (d) The Halons in presence of hydrogen (from water vapor or combustion process), will decompose into Hydrogen Fluoride (HF), Hydrogen Bromide (HBr), free Bromine (Br2), Carbonyl Halides (COF2, COBr2), Hydrogen Chloride and free Chlorine, which are highly toxic. 0271. Halon 2402 (Freon 114 B2) and Halon 1301 are used in major fire fighting systems, while Halon 1211 (BrCClF2) (also known as BCF) are used in portable extinguishers. The flame extinguishing ability of Halon 2402 vapours are very good and quite similar to that for Halon 1301 and Halon 1211. However, it is in liquid form. Halon-gas extinguishers are effective against electrical fires without causing low-temperature stress effects to electronic equipment. They can also be used for Class B, C and E fires. It is somewhat less effective with Class A fires. Halons are not to be used on Class D fires. Halons put out fires by choking off oxygen. The Halon gas is a non- reactive ChloroFluoroCarbon. Nomenclature 0272. The first digit of the number represents number of carbon atoms in the compound molecule, the second digit number of fluorine atoms the third digit number of chlorine atoms the fourth number of bromine atoms, the fifth digit is number of iodine atoms (if any ). hydrogen is not numbered. Eg :- CCl4 - Halon 104, CH3 Br - Halon 1001 Br CCl F2 Halon 1211 AND Br CF3 - Halon 1301. Following is the example of the nomenclature for Halon 1301:- 1 3 0 1 [] RESTRICTED 2-19  RESTRICTED INBR 1835 (I) C F Cl Br I Here, toxicity increases from F to I and the extinguishing properties also increase from F to I. Halon - Substitutes and Alternatives 0273. In the light of unprecedented environmental problems, the international community through the United Nations Environment Program has formulated the Montreal Protocol for the phase out of ozone depleting substances, which include ChloroFluoro-Carbons, Methyl Chloroform, Carbon Tetrachloride, Halons and others. The protocol had prescribed 01 Jan 1995 as the deadline for the phase out in the developed countries, while for the developing countries the phase out deadline is 01 Jan 2010. Keeping in view the Montreal Protocol, following actions are to be ensured by all units :- (a) Create Halon bank in the Navy by creating proper storage facilities. Procure and store the estimated quantity of Halon in the bank to meet the requirements till the year 2010. (b) Strict control is instituted for proper upkeep and maintenance of fire fighting systems to prevent wasteful discharge of Halon to atmosphere due to faulty systems. (c) Discharge for training is discontinued, and in lieu, portable CO2 extinguishers be used for training purposes. (d) The bottle pressure in the case of Halon 1301 and liquid level in the case of Halon 2402 system be monitored on weekly basis and defects are attended to without delay. (e) To avoid any leakage, cylinders should be pressure tested every 10 years. 0274. Following the footsteps of the Montreal Protocol of 16 Sep 1987, which necessitated phasing out of new production; the Kyoto Protocol agreed on the 10 Dec 1997 and committed the parties to specific reductions in the release of Global Warming Gases. The most significant alternative for the fire protection industry is considered Carbon Dioxide and hydrofluorocarbons (HFCs). The new EC Regulation 2037/2000, which came into force on 01 Oct 2000, states that:- (a) New Halons cannot be used for refilling existing systems. (b) Recovered, recycled or reclaimed Halon 1301 / 1211 can only be used in existing systems until 31st Dec 2002. After this date no refilling can take place. (c) Mandatory decommissioning of fire extinguishing systems with Halons must be completed before 31st Dec 2003. 0275. Deciding on a fire protection strategy when replacing Halon fixed-flood extinguishment or inerting systems in existing facilities or for new designs, is challenging. It is manifested, that any Halon replacement (Halon-like) or alternative (everything else) should have the same characteristics as Halon without potential adverse environmental effects. The main characteristics that are looked for in a replacement/alternative include: RESTRICTED 2-20  RESTRICTED INBR 1835 (I) (a) Comparable effectiveness to Halon. (b) No or minimal toxicity as a pure compound and after exposure to fire. (c) Stability of the compound (e.g., thermal, material compatibility). (d) Nil Ozone Depletion Potential (ODP) and Global Warming Potential(GWP), if possible. (e) Impact on the fire fighting system (e.g., weight and volume competitiveness). (f) A clean extinguishment (no residue). (g) Rapid knock-down of flames. (h) Not electrically conductive. (j) Suitable for inerting applications. (k) Compact and long term agent storage. 0276. There are two mechanisms for extinguishment, one mainly chemical and the other mainly physical. Chemical agents extinguish fires primarily by interfering with the chemical reactions of the fire, whilst physical ones operate by removing heat. Generally, chemically acting agents provide much faster extinguishment. Halon 1301 and CF3I are mainly chemically acting agents, whereas HFC-227ea, HFC-23 and C4 F10 are mainly physical acting agents. 0277. It is unlikely that a drop-in replacement agent will be discovered that will exhibit all of the beneficial properties of Halon 1301 and not also exhibit a significant environmental impact. Effective alternative chemical agents identified have weight and volume penalty associated with them. In addition to the chemical replacement agents, promising alternative fire extinguishing systems such as water mist systems and inert gas generators are under consideration by the Navy for some applications. Chemical Substitutes for Halon 0278. The chemical substitutes of Halon are also known as clean agents. They are electrically non- conducting, volatile, or gaseous fire extinguishing agents that do not leave a residue upon evaporation. They all have rapid discharge (approximately 10 seconds) and offer effective fire suppression. Some of the substitutes are mentioned below. 0279. FC-3-1-10 (Chemical name: PerFluoroButane (C4F10); Trade name PFC-410). It has a zero ODP but a high GWP and a very long atmospheric lifetime. It can be used in occupied spaces. 0280. HFC-227ea (Chemical name: HeptaFluoroPropane (CF3CHFCF3); Trade name: FM-200). It is the closest alternative extinguishing agent of Halon. It has the lowest GWP and the shortest atmospheric lifetime. It is non-conductive, clean agent leaving no residue. It achieves effective fire RESTRICTED 2-21  RESTRICTED INBR 1835 (I) extinguishment by physical cooling of the fire (80%) and by interrupting the chemical reaction of fire (20%). It is safe to use on energized electrical equipment. It is stored in cylinders of similar design to those of Halons and have similar discharge pipe work requirements. However, the volume required for its stowage is approximately 1.6 times more than that of Halon 1301. 0281. R-595 Blend. It is a blend of HydroChloroFluoroCarbons: HCFC-123, HCFC-22, HCFC- 124, Isopropenyl-1-Methylcyclohexane, having a Trade name of NAF S-III. It is one of the first commercially available alternatives to Halon 1301. However, because it is a HydroChloroFluoroCarbon (HCFC) and still has significant ODP, it is still classified as a transitional substance. It is stored in cylinders of similar design to those of Halon and has similar discharge pipe work. The amount of agent required to be stored, is marginally more than Halon 1301. 0282. HFC-23. (Chemical name: TriFluoroMethane (CHF3); Trade name: FE-13). A clean, non- conductive agent, which extinguishes fire by physical and chemical means. It requires almost twice the volume, for extinguishing a fire, than Halon 1301 alongwith the associated large storage and pipe work. It has zero ODP, high GWP and a long atmospheric lifetime. It can be used in occupied spaces as it has no adverse effects. It is not as efficient as Halon 1301 because it does not contain ozone-impacting Bromine. 0283. HFC-125. (Chemical name : PentaFluoroEthane (CHF2CF3; Trade name: FE-25). It has a zero ODP, high GWP but a relatively short atmospheric lifetime. Due to adverse toxicological effects, it is used only in unoccupied spaces. 0284. FIC-131 (Triodide). It is the only true replacement for Halon 1301available, in terms of the amount of agent required to achieve extinguishment. It has almost a zero ODP and a GWP comparable to Carbon dioxide. However, it poses a serious risk of cardiac sensitization to personnel exposed to the high levels of design concentrations. Therefore, it is used for unoccupied spaces, only. Non- Chemical Substitutes for Halon 0285. Carbon dioxide. (Discussed earlier). 0286. Nitrogen Based Inert Gases (Inergen and Argonite). Inergen is a mixture of inert gases: Nitrogen (50%), Argon (40%), Carbon dioxide (10%). Argonite is mixture of Nitrogen (50%), Argon (50%). Both these agents are a blend of atmospheric gases, have zero ODP, GWP and atmospheric lifetime. There are therefore no environmental restrictions for their use. They require extinguishing concentration of approximately 34% minimum and work in a similar manner as CO2 ie, by reducing oxygen concentration below the level necessary to support combustion. However, unlike CO2, they are not liquefied and require far more cylinders (8 times more than FM200) and a equally larger storage area. They are high pressure gases stored in excess of 15 to 30 Mpa, and therefore require special high-pressure pipe work. Owing to the long discharge time and the agent volume, inert gases generally are not suitable for rapidly escalating hydrocarbon fires or explosion inertion, in occupied areas of the ship. 0287. Water Mist. Water systems offer an environmentally acceptable solution as they do not contribute to ODP or Global Warming. In addition, there do not form any dangerous decomposition products. Water mist is defined as water having a droplet size of 1000 microns. It combats fires by RESTRICTED 2-22  RESTRICTED INBR 1835 (I) cooling, oxygen displacement and radiant heat attenuation. Because of the small droplet size (and hence high surface area to volume ratio), the efficiency with which they can absorb heat is far more than the water spray produced from conventional sprinklers. As the water mist absorbs heat from the fire, it gets converted to steam expanding up to 1700 times by volume. This rapid expansion of mist into steam momentarily displaces the air around the fire, resulting in oxygen starvation. It also creates a cooling effect on the surrounding objects in the vicinity of a fire, by attenuating the radiant heat. It also cleans, absorbs smoke and irritant gases particulate, which can be more damaging than a fire itself. These systems can be activated instantly and has minimal water loss. However, the complexity of these systems is due to the high pressures required, ranging upto 200 bar and the nozzle design technology for providing fine atomisation, with no clogging. Water Mist fire protection systems find application in Turbine Hoods, Flammable Liquid Storage, Machinery Rooms (such as elevator equipment rooms), Emergency Generator Rooms, Switch Gear Rooms and Engine Rooms. 0288. Traditional Sprinkler Systems. Extremely small droplets have insufficient momentum to reach the fire while large droplets provide a better trajectory and penetration, but do not absorb heat as effectively. Water sprinkling systems demand high water supply rates and are associated with fixed large bore pipe networks around the protected area. They do not have the problems associated with storage, high pressures, fine orifice of sprinklers and piping material. Sea water in marine environment can also be used in these systems. 0289. Powdered Aerosols. These are primarily pyrotechnically generated fire extinguishing aerosols, that chemically interrupt the chain reaction of fire by producing nitrogen, water and potassium compounds. The aerosol does not use the method of smothering nor by cooling, but inhibits a chemical combustion reaction on a molecular basis, without affecting the oxygen content. Chemically, the aerosols are made up of potassium compounds and other small quantities of gas particles, which when in contact with moisture are corrosive on some materials such as aluminium, making them unsuitable for clean environments. The aerosol is composed of micro particles which are suspended in an inert gas, so the ratio between the exposed surface and the reaction mass is extremely high. This, in turn, minimizes the required quantity of active extinguishing material. Particles of potassium compounds, with such minute measurements, remain suspended for a relatively long time, allowing them to flow into the natural convection currents present during combustion. This results in a increased efficiency of the extinguishing agent. Comparison of Halon Alternatives 0290. Table 2.4 lists the relative properties of common Halon alternatives:- Properties CO2 FM200 FE-13 NAFS-III Argonite Triodide Ozone depletion 0 0 0 0.044 0 0 potential Atmospheric 0 31