Arson 1st Exam Reviewer PDF

ARSON 1ST EXAM REVIEWER: If one or more of these elements in the fire triangle is removed, the correct combination is disturbed, the triangle CHAPTER I: THE SCIENCE OF FIRE...

ARSON 1ST EXAM REVIEWER: If one or more of these elements in the fire triangle is removed, the correct combination is disturbed, the triangle CHAPTER I: THE SCIENCE OF FIRE falls apart and the fire is extinguished. Fire Behaviour the manner in which the fuel ignites, flame There are also products that can interfere with the chemical develops, and fire spreads. Used to distinguish reaction of the flame: characteristics of one particular fire from typical fire characteristics. Halon a dry chemical powder cloud or used as an effective way of extinguishing a fire. COMBUSTION a chemical process caused by the combination of one or more substances with oxygen. Theories of Combustion Combustion is a complex sequence of exothermic chemical 1. Fire Triangle Theory reactions between a fuel and an oxidant. - Three elements necessary to create/produced fire in equal proportion; (H.O.F) Fire is a rapid, self-sustaining oxidization process accompanied by the release of heat and light of different 2. Fire Tetrahedron Theory intensities. - The fourth element of fire known as the BG "Chemical chain reaction." A fire can be started and sustained only when fuel and oxygen are available in the correct ratios. 3. Life Cycle of Fire Theory \ The only fuel that can burn is the fuel in a vapour or - Stages/steps wherein fire is created. gaseous state. Fire Triangle: Oxygen, Heat, and Fuel A heat source is required to produce these vapours at the surface of the solid or liquids. The quantity of heat required A. Heat - a form of energy measured in degree of to initiate the process depends on the combustibility of the temperature, the product of combustion that caused the materials. spread of fire. For a fire to start there must be a source of ignition, usually heat or a spark. In solids and liquids, the process of combustion takes place in two stages, the two stages happen almost Heat sources include: Open flame, Hot surfaces, Electrical simultaneously. circuit, Friction, Sparks, All sources of ignition The required fuel: oxygen for burning vary and are Common Sources of Heat (Types of Energy) determined by the specific fuel. - Chemical Energy - Most liquids cease to burn if the oxygen content is reduced - Electrical Energy to 10%. - Nuclear Energy - Solid materials may continue to burn or at least smoulder - Heat until the oxygen content in the air is reduced to 6% - Light - Gases and dust clouds ignite in relation to air supply in the same way as flammable vapours. 1. Chemical Energy - the most common source of heat in combustion reactions. A source of ignition/heat, which starts the chemical process When any combustibles is in contact with oxygen oxidation of combustion, requires sufficient energy. (100 degrees) occurs. Conditions for a Fire: Examples: - heat generated from a burning match - self-heating (spontaneous heating) 2. Electrical Energy - when electrons flow through a conductor. - Heat is produced when the new molecules are formed. Factors involving Electrical Heating: The resultant products of combustion are heat, smoke and - current flow through a resistance toxic gas.. - arcing - sparking Fire Triangle: H.O.F - static - Heat, Oxygen, Fuel - lightning 3. Nuclear Energy - when atoms either split apart (fission) or combine (fusion). Common types of solids: Nuclear power plants generate power as a result of the fission of Uranium-235. Examples: - fission heats water to drive steam turbines and produce electricity - Bib 10- the solar energy is a product of a fusion aisidilanoma reaction (a form of nuclear energy) 4. Mechanical Energy - An energy created by friction and compression. Fire Tetrahedron a new theory that explains combustion Heat of Friction - the movement of two surfaces against and extinguishment (W.M. HAESSLER). each other. This movement produced sparks being generated. The combustion reaction can be characterized by four components: Heat of Compression - heat is generated when a gas is - fuel compressed in a container or cylinder. - oxidizing agent - heat Energy exists in two types: - an uninhibited chemical chain reaction. Potential Energy an energy possessed by an object that These four components have been classically symbolized can be released in the future. by a four-sided solid geometric form called a tetrahedron. Fires can be prevented or suppressed by controlling or Kinetic Energy - an energy possessed by a moving object. removing one or more of the sides of the tetrahedron. 5. Heat Four Ways to Extinguish Fire - an energy that is transferred between two objects of - Starving the fire or fuel : Isolate the fuel supply differing temperature such as sun and the earth. - Removing the heat source : Cooling - Reducing the oxygen content : Inert (Suffocation) 6. Light - Uninhibited Chemical Reaction : Inhibition/Interruption - a visible radiation created at the atomic level such as flame produced during combustion. Removal of any side of the fire tetrahedron, that is: fuel, heat, oxygen or the chain reaction. results in extinguishment B. Oxygen a colorless and odorless gas and one of the of the fire. composition of air that supports fire which is approximately 21% by volume. Elements of Fire Tetrahedron - Approximately 16% is required. Normal air contains 21% oxygen. Some fuels contain enough oxygen within their 1. Oxidizing agent (oxygen) material/substance that yield make-up to support burning. or provides oxygen or oxidizing gases - Oxidizers are not themselves combustible, but they Oxygen Sources: support combustion when combined with fuel. 1. 21% of normal oxygen 2. 78% of nitrogen d Common Oxidizing Agents: 3. 1% of other gases 1. Bromates 2. Fluorine Oxygen Requirements: 3. Nitrites 1. 12% no fire 4. Bromine 2. 14% flash point 5. Iodine 3. 21% fire point 6. Perchlorates 7. Chlorates C. Fuel - any substance/combustibles which reacts 8. Nitrates chemically with oxygen and produces flames. For a fire to 9. Permanganetes start there must be something to burn. 10. Chlorine 11. Nitric acid Fuel Sources (Physical State): 12. Peroxides Solid molecules are closely packed together Liquid molecules are loosely packed Gas molecules are free to move 2. Reducing agent (Fuel) material or substance being Transmission of Heat the transfer of heat from the initial burned in the combustion process. source to other fuels in and beyond the area of fire origin. - the fuel in a combustion reaction Types: 3. Temperature (Heat) the energy component of the fire tetrahedron. Conduction - a fire heated object is in direct contact with another, cooler object and heated. Temperature is an indicator of heat and is measure the warmth or coldness of an object based on some standard. Convection - heat transfer that occurs when the fire heats - freezing (32 degrees F and 0 degrees C) the air near it, causing the heated air to rise. - boiling points (212 degrees F and 100 degrees C) of water. Radiation - transfer of heat through light/heat waves. Temperature is measured using degrees Celsius in SI and degrees Fahrenheit in the Customary System. Direct Flame Contact - fire spreads along or through a burning material by flame contact. 4. Self-Sustained Chemical Reaction - (the fourth element) - This process is necessary for continuous combustion. This Burning will continue until: sustained combustion process is what referred to as chain - fuel is removed or burned away;. reaction. - oxygen is removed or its level is lowered to a point where burning will stop; Life Cycle of Fire Theory (Stages of Combustion) - heat is decreased to a point where molecular activity can wherein fire is created. no longer sustain a fire; - uninhibited chain reactions are interrupted. Combustion Reaction/Process: - Causes pyrolysis or vaporization of solid and liquid fuels and the production of ignitable vapours or gases; - Provides the energy necessary for ignition; - Causes the continuous production and ignition of fuel vapours or gases to continue the combustion reaction. Ignition Source The Nature of Fire Pyrolysis the chemical process whereby fire consumes the FIRE CHARACTERISTICS AND CLASSIFICATIONS: most solid part of the fuel. It is the thermal decomposition of a solid fuel through the action of heat. What Makes a Fire Burn: fuel, heat, oxygen, and the chemical reaction (fire The Process of Pyrolysis: tetrahedron). Removing any of the four elements fire will not - The fuel is heated until its temperature reaches its fire occur. point; - Decomposition takes place - moisture in the fuel is What Makes a Fire Grow converted into vapour; undergoes through three phases of burning; - Decomposition produces combustible vapours that rise to the growth phase (Incipient stage), the surface of the fuel. These combustible vapours are the fully developed phase (Free-burning stage) in which technically termed as free-radicals; all of the materials involved in the fire - Free-radicals undergo combustion if proper amount of the decay phase (Smouldering stage) in which the oxygen is present. amount of available fuel is reduced as the fire consumes the material. It takes place for most fires involve in an outdoor The Most Common Type of Free-radicals (combustible area that is free of any confinement. vapours): flashover - smoke and heated gases combine with the right 1. Hydrogen gas amount of heat and oxygen ignite. 2. Carbon Monoxide 3. Carbon Dioxide Propagation of Fire - Propagation of fire simply means the 4. Nitrogen spread of fire. Products of Combustion: Based on Smoothness: Thermal: Heat, Flame 1. Laminar flame - (smooth flame) flame is laminar when a Non- Thermal: Smoke, Gases particle follows a smooth path through a gaseous flame. 1. Fire gases the chemical composition of the fuel, 2. Turbulent flame (rough flame) those having unsteady, percentage of oxygen present, and the temperature of the irregular swirls and eddies. fire Carbon Monoxide, which is also produced by slow 3. Heat a form of energy generated by the transmission of oxidation, is found in sewers, caves, wells, mines, stove some other form of energy. furnaces, and automobile exhaust. Heat - a form of energy measured in degree of temperature Types of Poisonous Gases: it is the product of combustion that spread the fire. Hydrogen Sulfide (H2S) a fire gas formed during fires 4. Smoke a visible product of incomplete combustion, a involving organic material containing sulfur, such as: mixture of oxygen, nitrogen, CO, CO2 and finely divided Rubber, hair, wood, meat and hides. particles released from the burning material - toxic gas with strong odor of rotten eggs. Lesson 1.2 Hydrogen Cyanide (HCN) - a toxic fire gas found in oxygen-starve fires involving nitrogen-containing materials PROPERTIES FIRE such as: Wool, silk, urethane, polymides, and acrylics. - also used as a fumigant which can pose serious danger to A. Physical Properties firefighters - smells like bitter almonds which may not be easily Fire Point detected. - the lowest temperature at which a product produces sufficient flammable vapour to produce sustained Hydrogen Chloride (HCL) - a gas which can be fatal after combustion after the removal of the primary source. only a is produced in fires involving chloride-containing plastic. Flash Point - The lowest temperature at which a product produces 2. Flame - The luminous body of a burning gas which gets enough vapour to produce a flash through the application of hotter and less luminous when mixed with more oxygen. a small ignition source near the surface of the product. Specially to liquids, but it can also apply to some solid Flame is the visible (light-emitting) part of a fire. It is caused materials. by a highly exothermic reaction taking place in a thin zone. - If a fire is hot enough to ionize the gaseous components, it Ignition Temperature can become a plasma. - The temperature at which the material is heated to initiate sustained combustion, once ignited. Types of Flame: Auto-Ignition Temperature A. According to Color and Completeness of - the temperature at which the heat evolved by a material Combustions. decomposing under the influence of heat is sufficient to bring about combustion without the application of an external 1. Luminous flame source of ignition. - a reddish-orange in color; - this temperature is normally higher than the ignition - a product of incomplete combustion; temperature. -it has lower temperature. Flammable Limits 2. Non-luminous flame - are the minimum and maximum concentrations of a gas or - bluish in color; vapour in air which can be ignited and sustain a - a product of complete combustion; self-propagating flame. - it has a higher temperature than luminous flame Flammable Range B. According to Burning Fuel and Air Mixture: - the range of flammable vapour or gas/air mixture between the lower and upper flammable (explosive) limits. 1. Premixed flame example of a Bunsen burner Specific Gravity 2. Diffusion flame example of flame of the oxyacetylene - Is the ratio of the weight of the material to the weight of the torch (diffused-dispersed; widely spread). same volume of water. Vapour Density - When more than one single component is present in the - term used to explain the weight of vapours liquid fuel, e.g. crude oil, the temperature will rise to the - if a substance has a vapour density of 1.5 it is boiling point of the lighted product. The temperature is called one-and-a-half times as heavy as air under the same the Initial Boiling Point (IBP). conditions of pressure and temperature. If a substance has a vapour density of 7 it is lighter than air, weighing only 7/10 as B. Gases much as an equal volume of air. - Gases are vapours and ignite in one single stage without - Is the weight of a volume of pure gas preliminary warning. - If the gas is stored under refrigerated conditions, the liquid Boiling Point has to be warmed up/heated before gases/vapours are Petroleum products do not have a specific boiling point, but produced. have a boiling range. - initial boiling point (IBP) the lowest temperature in the C. Solids boiling range - Solids can be destroyed by the slow process of thermal - final boiling point (FBP) maximum temperature when a decomposition, which produces an increasing amount of liquid is evaporated vapours at higher temperatures that the material is gradually becoming ready for ignition. Solids need an external source Catalyst of heat to raise the temperature at which they will produce - when added to a system, will control the spread of reaction. flammable vapours. Vapour Pressure CONCLUSION - the lowest pressure at which a liquid at a given temperature - In case of fire, the effective method of suppression is to in a closed container will remain in the liquid phase without bring the products back into a state that combustion will stop. evaporation. Lesson 1.3 B. Chemical Properties: MATERIAL CLASSIFICATION 1. Endothermic reaction are changes whereby energy (heat) is absorbed Combustible Materials - All materials, such as solids, gases and liquids are 2. Exothermic reaction changes that release or give off combustibles, depending on the temperature the product is energy (heat) thus they produce substances with less energy called combustible when its flashpoint is 38 degrees or than the reactants. higher. 3. Oxidation a chemical change in which combustible Flammable Material material (fuel) and an oxidizing agent react. - Most materials are flammable; when ignited, the product will immediately catch fire, without raising the temperature of 4. Combustion/flame the manifestation of fire when the material. the fire is in its gas-phased combustion. A matter that is produced by fire. EUROPEAN CLASSIFICATION OF FUELS: Class A - Carbonaceous substances (solids) Oxidation Class B - Liquids - at the very slow end of the time spectrum where the Class C - Gaseous Products reaction is too slow to be observed. Flammability Limits and Class D - Light Metals Density of Vapours and Gases U.S. CLASSIFICATION OF FUELS: – Class A - Carbonaceous substances (solids) Class B - Liquids and Gases Behaviour of Fuel in Combustion Class C - Electrical Material Class D - Metals A. Liquids - A combustible liquid does not combine directly with oxygen Classification of Fire: in the burning process. This is because the liquid has to be first turned into a flammable vapour before ignition can A. Based on Cause: occur. 1. Natural fire - Other combustible products such as fuel oil may require 2. Accidental fire considerable heating before sufficient vapours are produced 3. Intentional fire to make ignition possible. Each product has a specific temperature at which it can be ignited called FLASHPOINT. B. Based on Burning Fuel - Five (5) Classes of Fire 1. Class A CHARACTERISTICS OF FLAMMABLE MATERIALS - vegetable fibres, wood, paper straw, grain, and grass; combustible minerals such as coal and coke. Nearly all thrash fires are considered as Class A. Petroleum products are those which are manufactured from crude oil. CLASS A FUELS: Wood, Paper, Rubber, Plastic All matter, including flammable materials will exist in at least 2. Class B one of three states: - petroleum products such as gasoline, fuel oils, lubricating 1. Liquids oils, and greases; animal fats such as butter, lard, and tallow; 2. Gases vegetable extracts such as alcohol, linseed oil, and 3. Solids turpentine; vegetable compounds such as shortenings and oleomargarines; natural gases and compressed gases such Liquids as butane, propane, hydrogen, and acetylene - do not generate more than 40 psia when heated to 100 degrees F (psia is pound-per-square inch absolute). 3. Class C - electrical motors, electrical appliances and apparatus. To determine whether a fluid should be classed as a gas or a Actually Class C fire is composed usually of Class A and liquid, it is tested. Procedures in testing: READ BOOK Class B materials or a combination of both. Use of water is usually dangerous because of the risk of electrical shock. identify the fluid as a gas. (over 40 psia). If the gauge reading is 25 psi and the atmospheric pressure is 14.7, the 4. Class D sum would be 39. 7. The fluid would be just within the liquid - combustible metals, alloys, or metal compounds either in a class. solid, semi-solid or liquid state. Types of Liquids 5. They may further reduce in shavings, grindings, granules, or dust. Some liquid metals are kept in a liquid state under Flammable Liquids pressure. Usually these liquid metals are extremely - liquids with a flashpoint below 100 degrees F and a vapor dangerous.- sodium (NA), magnesium, titanium, sodium pressure sure not over 40 psia at 100 F. potassium, and uranium as well as pyrophoric organometallic reagents such as alkylithiums, grignards and CLASS I LIQUIDS diethylzinc. These type of materials burn at high - Having a flashpoint below 37.8 degrees C (100 degrees F) temperatures and will react violently with water, air, and/or and subdivided into the following classes: other chemicals. Class IA 6. Class K - any liquid that has a flashpoint below 73 degrees F (22.8 - materials involved in the kitchen fires. This classification degrees C, and a boiling point (BP) below 100 degrees F was added to the NFPA portable extinguishers Standard in (37.8 degrees C). 1998. Class IB The classification of electrical fires is an indication of - any liquid that has a flashpoint below 73 degrees F (22.8 possibly high voltage; The fire as such in electrical degrees C), and a boiling point at or above 100 degrees F equipment involves a carbonaceous material. It is (37.8 degrees C). appreciated that the presence of live electrical conductors may determine a specific response. Class IC In the U.S. system there is one class for "gas and liquids" - any liquid that has a flashpoint below 100 degrees F (37.8 which require in most cases a different response. C) but not below 73 degrees F (22.8 C). flammable liquid Combustible Liquids - any liquid having a flashpoint below 37.8 degrees C (100 - liquids that have a flashpoint at or above 100 degrees F degrees F) and having a vapour pressure not exceeding 276 (37.8 C) and subdivided into the following categories: kpa (40 psig) at 37.8 degrees C (100 degrees F) Class II - - any liquid having a flashpoint at or above 100 degrees F (37.8 C) and below 140 degrees F degrees C). (60 Class IIA - any liquid having a flashpoint at or above 60 degrees C (100 degrees F) and below 93.3 degrees C (200 degrees F) Lesson 1.4 MATERIALS Class IIIA 1. Chemical Properties chemical properties of gases are of - any liquid having a flashpoint at or above 140 degrees F prime interest to firefighters, as they reflect the ability of the (60 degrees C) and below 200 degrees F (93.3 degrees C). gas to react within it or with other materials. Class IIIB The chemical properties of gases may be broken down as - any liquid having a flashpoint at or above 93.3 degrees C follows: (200 degrees F). Flammable gases Types of Flammable Liquids: - any gas that which burn in normal concentrations of oxygen in the air. These gases are subjected to the same conditions Hydrocarbons as flammable vapors. a) alkanes b) alkenes Non-flammable gases c) alkynes - gases that will not burn in air. d) aromatics - oxidizers - support combustion. - inert gases - do not support combustion Halogenated Carbon a) alcohol Reactive gases b aldehydes - any gases that will react within itself or with other materials c) amines under conditions other than fire, i.e. shock, heat, and etc. d) ethers e) ketones Toxic gases f) esters - any gases that may complicate firefighting efforts due to its serious life hazards. Hazards of Flammable Liquids: Produce Vapours that: 2. Physical Properties is the physical behaviour of a gas burn both outside and inside its container and when accidentally corrosive released, these are of prime interest to firefighters. oxidizers toxic The Physical Classification are the following: narcotic unstable Compressed gases - matter which is solely in a gaseous state in its container Slopover - a reaction wherein water trapped at bottom of with a lower pressure limit of 25 psig (pounds per square storage tanks vaporizes from heat expanding and expelling inch gauge) at normal temperature berature of 70 degrees F contents above it. to 100 degrees F. BLEVE (BOILING LIQUID EXPANDING VAPOUR EXPLOSION) BLEVE - a rupture of a vessel containing a liquid above its Liquefied gases normal atmospheric-pressure boiling point may result in - matter which exist partly as a gas and partly as a liquid at explosive evaporation of a large part of its contents. normal temperatures inside the container and remain under pressure as long as any liquid is in the container. If the material is flammable and an ignition source is present, the consequence will be a "fire ball" with a blast Cryogenic gases effect in the total area. - gas which remains as liquefied gas in its container at temperature far below normal temperature. CAUSES OF BLEVE: Usage Classification of gases: a. Fuel gases - gases which burn with air to produce heat, power, or light. b. Industrial gases - gases used in industrial processes such as: water treatment, welding and cutting, refrigeration, and etc. Gases c. Medical gases - gases used for medical purposes such - classified by their chemical, physical properties, and usage. as therapy and anesthesia. Flammable Compressed Gas: 2. Titanium 3. Uranium 1. Natural GasThe most common flammable gas 4. Zirconium 5. Magnesium 2. Methane lighter than the air and not toxic 6. Potassium 7. Lithium 3. Propane and Butane colorless, tasteless, odorless, and 8. Sodium-potassium alloys not toxic, heavier than air Combustible Solids 4. Acetylene colorless, tasteless, odorless, shock sensitive, 1. Wood burns ethylene 4217 degrees F 2. Carbon a) Coal & charcoal 5. Hydrogen difficult to keep in container lighter than air - b) Carbon monoxide extremely flammable c) Carbon dioxide 6. Ethylene Oxide gas at room temperature extremely wide carbon monoxide is flammable, burns very hot explosive range - 3.0 to 100% 3. Phosporous 7. Oxidizer can burn inside its own container a) Pyrophoric - reacts violently when it contacts air b) Bombs, pyrotechnic devices Non-Flammable Gas: 4. Sulfur 1. Oxygen most common does not burn supports - non-toxic in elemental form, sulfur dioxide formed when combustion burn, toxic 2. Ammonia non-flammable - but does burn, flammable 5. Metals range is less than 10% water soluble 6. Cellulose Nitrate common, flammable, toxic, clear plastic 3. Refrigerants may be toxic when heated materials, oxidizing agent 4. Halogens: 7. Ammonium Nitrate explosive, oxidizing agent fertilizer, explosive when contaminated with fuel a) Fluorine most powerful oxidizer, extremely toxic, extremely reactive, water reactive 8. Other Nitrates must be considered flammable and/or explosive liberates toxic nitrogen oxides b) Chlorine toxic, corrosive, irritating 9. Solids with Flashpoints 5. Acid Gases turn to acids when dissolved in water toxic, corrosive, irritating a) Naphthalene Does not burn, gives off flammable vapors at 174 degrees F. 6. Inert Gases: a) Helium Lesson 1.5 HAZARDOUS MATERIAL IDENTIFICATION b) Nitrogen c) Argon Hazard Classification d) Carbon dioxide e) Krypton f) Neon 7. Other Gases UNO Classes of Dangerous Materials: Solids Class 1 Explosives divided into four divisions which indicate Combustible solids the type of hazards expected.: - those which ignite burn and change chemically when subjected to heat or fire. A. Class Division 1.1 - heat must be approximately 350 degrees F or higher. - Mass detonating explosives comparable to Quantity- Distance (Q-D) Class 7 and M designated items. Combustible Metals most of combustible metals are - Assigned to this class are principally blast hazards. They chemical elements which are part of earth's composition. may be expected to mass detonate when a small portion is Some of the combustible metals are the following: initiated by any means, such as fire, severe concussion or 1. Sodium impact impulse of an initiating agent.  STAGES/PHASES OF FIRE B. Class Division 1.2 - Non-mass detonating, fragment producing explosives. Factors to be considered in determining phases of These items for which the principal hazards may be burning: fragments, toxicity, or blast. 1. The amount of time the fire has burned; 2. The ventilation characteristics of the confining structure; C. Class Division 1.3 3. The amount and type of combustibles present - Items assigned to this class usually burn vigorously with little or no possibility of extinguishing fires that have gained Chapter II: Stages/Phases of Fire headway in storage situations. 1. Incipient/Ignition Phase D. Class Division 1.4 - Ignition describes the period when the four elements of the - It includes explosives with a moderate fire hazard, but no fire tetrahedron come together and combustion begins. blast hazard. Items assigned to this class primarily present When fuel and oxygen are present in the correct ratio, an fire hazards producing no blast and virtually no initial source of heat present causing ignition by any of the fragmentation or toxic hazards beyond the normal fire hazard following: (clearance) distance. Characteristics: Class 2 - Gases: Compressed, liquefied or dissolved under Point at which fire starts. pressure. Ignition source available. Plenty of oxygen, approximately 20%. Class 3 Flammable Liquids Temperature is slightly over 38 degrees. Little heat and smoke. Class 4 - Flammable Solids There are rising hot gases. Fire is small and generally confined to the fuel first ignited. Class 5 - Oxidizing Substances and Organic Peroxides Plume Forming Class 6 - Poisonous (toxic) and Infectious Substances PLUME DEVELOPMENT - Initially, the temperature of the fire gases decreases as they A. Class Division 6.1 substances: Poisonous (toxic) gas, move away from the centerline of the plume. vapors As the fire grows, the overall temperature in the These materials are comparable to Q-D Class 8, which compartment increases as does the temperature of the gas includes those CB agents and items not normally assembled layer at the ceiling level. with explosive components, or where explosive components present little or no blast or fragment hazards. No quantity- 2. Free-burning/Growth Phase distances separations have been specifically established for - Once a reaction between the fuel and oxygen has started, this class as a whole. Special safety criteria or instructions the combustion can be rapid. A gas explosion or dust have not been provided with the stock involved and safety explosion can develop in seconds. Fires of solid material separation appears necessary because of agent persistency, develop "slowly" compared to fires of combustible liquid volatility, toxicity, or other particular feature, requests for products. information should be made to higher headquarters. - In free-burning fire smoke and superheated gases collect at the ceiling level. B. Class Division 6.2 Substances containing disease- - A condition where flames move through or across the producing micro-organisms. This class division category is unburned gases during the fire's progression. included for information only. Characteristics: Class 7 Radioactive Substances Fire has involved more fuel Oxygen supply is depleted Class 8 Corrosives Heat accumulates at upper area Temperature exceeds 1,300 degrees F (705 degrees C) Class 9 - Miscellaneous dangerous substances (substances Area is fully involved which present a danger not covered by the other classes). PRE-FLASHOVER CONDITION EMERGENCY ACTION GUIDE FOR HAZARDOUS - The radiant heat (red arrows) from the hot gas layer at the MATERIALS (book) ceiling heats combustible materials which produces vapours (green arrows) CHAPTER II Flashover: Characteristics  ​ Heat build-up. ​ Room contents heated to ignition temperatures. applying water to the upper level of the thermal layer ​ Simultaneous ignition of all combustibles in room. creates a thermal imbalance. ​ Transition between growth and fully developed stages and is not a specific event. Pulsation Cycle ​ Conditions change very rapidly as the fire changes - an indication of the presence of unburned fuel vapours from one that is dominated by burning the first within a compartment with the potential for pre-mixing and a material involved to one that involves all of the potential explosion. exposed combustible surfaces within the compartment. ​ A warning sign for backdraft as smoke 'pulses' ​ Plenty of heat and smoke, which indicate rapidly intermittently in and out at a ventilation/entry point changing conditions. ​ Blueflames a warning sign preceding a backdraft ​ May involve all exposed combustibles. as noted by Grimwood. ​ Increasing levels of smoke with decreased visibility. Backdraft/Backdraught ​ High heat level (480-650 degrees Celsius) from - A smoke explosion caused by a sudden introduction of floor to ceiling. oxygen into a confined building or area. ​ Gases generated are heated by radiant energy from the gas layer at the ceiling. FIRE INTENSITY Rollover Characteristics The temperature in a solid fuel is 800 degrees centigrade, the temperature in a liquid or gas fire is 1200 degrees C ​ An eruption of flames following the ignition of gas plus. that has collected at the top of an enclosed space or structure. Intensity of Fire - means simply "how hot the fire is burning. ​ Rollover is the extension of the fire plume or tongues of flame that have become detached Factors to determine the intensity of fire: ahead of the plume at ceiling level signalling the 1. Type of fuel effect of 'rollover' a recognised warning sign that 2. Percentage of oxygen present the compartment fire is rapidly progressing towards "flashover". FIRE SPREAD (book) 3. Smouldering Phase/Decay the final phase of burning wherein flame ceases but dense smoke and heat completely fill confined the room. Characteristics: ​ Flames may die and leave only glowing embers or super heated fuel under pressure with little oxygen. Intensity of fire decreases due to lack of available fuel. ​ Intense heat will vaporize lighter fuel components, such as hydrogen and methane, increasing the hazard ​ Temperature throughout the building is very high and normal breathing is not possible. ​ Remaining mass of glowing embers can result in moderately high temperatures in the room for some time. ​ Oxygen deficiency may cause backdraft Thermal Layering of Gases (thermal balance) - is the tendency of gases to form into layers according to temperature. - the hot gases tend to be in the top layer, while the cooler gases form the lower layers. under normal fire conditions in a closed structure, the highest levels of heat will be found at ceiling level and the lowest level of heat will be found at the floor level.