Western Canada Mine Rescue, Chapter 10 PDF

Western Canada Mine Rescue Manual Chapter 10 Fire 10-1 OBJECTIVES Fire poses major hazards in the rescue and treatment of casualties. Burning structures and equipment must be addressed efficiently to rescue trapped and injured people, as well as to mitigate damage to infrastructure. Upon completion...

Western Canada Mine Rescue Manual Chapter 10 Fire 10-1 OBJECTIVES Fire poses major hazards in the rescue and treatment of casualties. Burning structures and equipment must be addressed efficiently to rescue trapped and injured people, as well as to mitigate damage to infrastructure. Upon completion of this chapter, the trainee shall be able to demonstrate competency in:  Components of personal protective equipment used in fire rescue  Fundamental characteristics of fire behaviour  Fire classes, phases, and hazards  Fire extinguisher classifications, types, and agents  Special conditions such as ventilation, equipment fires, and BLEVEs The information contained within this chapter in no way prepares or certifies the rescuer to perform interior structural firefighting. Always operate within your scope. PERSONAL PROTECTIVE EQUIPMENT Bunker gear (turnout gear) is the protective clothing that is required to perform fire rescue. This gear needs to be researched prior to the purchase to ensure that it meets the current applicable standards and site requirements. Fire-rated rescue clothing consists of:  Helmet: Protects the head from injury.  Protective Hood (balaclava): Protects parts of the face that are not covered by the collar or helmet.  Bunker pants and coat: Will protect the body from heat, cuts, and abrasions.  Gloves: Protect the hands from heat, cuts, and abrasions.  Bunker boots: Protect the feet from cuts and abrasions from the top and from the bottom.  Eye protection: Protects the wearer’s eyes from foreign matter.  Hearing Protection: Protects the ears from excessive noises.  Respiratory Protection: Protects against heated gases as well as toxic and oxygen-deficient atmospheres.  Personal Alert Safety System (PASS): Built into a breathing apparatus or attached to a rescuer. Care, Cleaning, and Storage of PPE  Manufacturer’s guidelines must be followed to ensure proper use, storage, and handling. All equipment used must meet relevant health and safety legislation, standards, and regulations. During an incident, rescuers may be exposed to biological, chemical, electrical, and fire hazards. Care should be taken to reduce exposure from contaminated PPE during and after an incident. 10-2 FIRE BEHAVIOUR Fundamental to a mine rescuer’s safety is a basic grasp of the physics and chemistry of a fire. States of Matter There are three states of matter: solid, liquid, and gas/ vapour. Two factors that can change the state of matter are heat and pressure. When substances are heated, they tend to change from the solid to the liquid state and then to the gas or vapour state. When substances are subjected to pressure, they tend to change from gas or vapour to liquid and then to solid. Materials as a rule will not burn while in their solid or liquid states. Materials must first change to gas or vapour and then burn. Factors Affecting Fire Behaviour Solid fuels have definite size and shape. The surface area of a solid fuel in relation to its mass is a primary consideration for the mine rescuer. The larger the surface area for a given mass, the more rapid the heating of the fuel and the process of pyrolysis will be. The physical position of a solid fuel is also important. If a solid fuel is in a vertical position, the fire will spread more rapidly than if it is in a horizontal position. Pyrolysis refers to the decomposition of organic material at high temperatures in the absence of oxygen. During pyrolysis, the material is heated to a point that both its physical state (e.g., solid) and chemical composition change at the same time. It usually produces gases, vapours, and particulates. 10-3 Liquid Fuels Liquid fuels have physical properties that increase both the difficulty of extinguishment and the hazards to personnel. Liquids will assume the shape of their container. When a spill occurs, the liquid will assume the shape of the ground and will flow and accumulate in low areas. The density of liquids in relation to water is often referred to as specific gravity (water = 1). Liquids with a specific gravity less than one are lighter than water. Those with a specific gravity greater than one are heavier than water. Most flammable liquids have a specific gravity of less than one. Hydrocarbon liquids, as a rule, will not mix with water. Gases and Vapours Gases and vapours tend to assume the shape of their container but have no specific volume. If the vapour density of a gas or vapour is less than that of air (air = 1), it will rise and tend to dissipate. If a gas or vapour is heavier than air, it tends to hug the ground. Fire Triangle Requirements for Burning Fire is a chemical reaction known as combustion. It is defined as the rapid oxidation of combustible material accompanied by a release of energy in the form of heat and light. Oxygen Fuel Fire Triangle The three-sided figure of the fire triangle describes the necessary components to create a fire. When oxygen, heat, and fuel in proper proportions combine they create a fire. If any one of the three elements is removed a fire cannot exist. Heat Fire Tetrahedron Some chemicals and materials will ignite and burn in a manner that cannot be explained completely by the use of the fire triangle. Some questions that defy explanation under this theory are:  Why will calcium and aluminium burn in a nitrogen atmosphere, in the absence of oxygen?  Why do some fuels burn more rapidly when subjected to radioactive emanations (gas)?  Why do flames react with certain sonic vibrations and electrically charged particles? Fire Tetrahedron Heat Uninhibited Chemical Chain Reaction Oxidizing Agent Reducing Agent (Fuel) 10-4 These questions can be answered by using the Fire Tetrahedron. One of the four components serves as the base and represents the chemical chain reaction. The removal of one or more of the four components will make this tetrahedron incomplete and result in extinguishment of the fire. This theory has not done away with the fire triangle. It has simply added a fourth condition. The four components of the tetrahedron are: Reducing Agent (Fuel): In the tetrahedron, fuel is defined as “a material that can be oxidized”. The term “reducing agent” references the fact that fuel reduces an oxidizing agent. Oxidizing Agent (Oxygen): The term “Oxidizing agent” explains how some materials, such as sodium nitrate and potassium chlorate (which release their own oxygen under certain conditions), can burn in an atmosphere free of any outside source of oxygen. For example, zirconium dust can be ignited in carbon dioxide without oxygen being involved. Examples of oxidizing agents are: Oxygen Nitric Acid Chlorates Hydrogen Peroxide Sulphuric Acid Chromates Fluorine Manganese Dioxide Nitrates Chlorine Lead Dioxide Bromine Temperature (Heat): Temperature refers to heat as a quantity of energy. Heat is energy in disorder and temperature is the measure of the degree of that disorder. Uninhibited Chemical Chain Reaction: This chain reaction refers to self-sustaining combustion that continues when heat from the fire radiates back to the fuel, even if the original ignition source is no longer present. In the burning of either liquid or solid fuels, the vapours, which are distilled off and carried into the flame, contain atoms or molecules that have not been consumed in the initial burning process. These liberated particles may have an electrical charge that either attracts other particles or repels them. This area, between vapour or gases and the visible flame, is called flame interface. Immediately above this area, oxygen molecules exist in sufficient number to produce energy reactions, which create light in the form of flames. This area is fed by the oxygen drawn into the fire as air currents move into the void created by the rising heated vapours or gases. This process continues throughout the flame. The molecular structure of the material is broken down, and the released atoms combine with other radicals and elements which are drawn into the process to form new compounds, which are again broken down by the heat. The final by-products then escape the flame in the form of smoke and steam. Since carbon is one of the elements most difficult to ignite, most of the visible smoke consists of unburned carbon particles. This is not a step-by-step process. All of the steps occur simultaneously in varying degrees of intensity throughout the flame. 10-5 Extinguishment Based on the fire tetrahedron, there are four methods of fire suppression:  Remove the reducing agent  Exclude the oxidizing agent  Reduce the temperature  Interrupt the chemical chain reaction Interrupting the Chemical Chain Reaction Vapourizing liquid and dry chemical agents extinguish fire more rapidly than the same quantity of other smothering agents. When these extinguishing agents are added to a fire, they release atoms that combine with the molecules involved in the chemical chain reaction. The new molecules formed by this process do not combine with the oxygen in the air that keeps the fire burning, thereby interrupting the chain reaction. CONCEPTS AND DEFINITIONS Ignition Temperatures Auto-ignition Temperature is the temperature at which a material will ignite spontaneously, independent of an external ignition source. Flash Point is the lowest temperature at which fuel will give off enough vapours to ignite when exposed to an external ignition source. Fire Point is the temperature at which a liquid fuel will produce vapours sufficient to support combustion once ignited. The fire point is usually a few degrees above the flash point. Ignition Temperature refers to the minimum temperature to which the material must be heated to initiate self-sustained combustion independent of an outside heating source. 10-6 Sources of Ignition Adiabatic compression involves compressing a liquid or gas to produce heat. This heat is generated by molecules running into one another and against the sides of the container. A flammable substance compressed quickly enough can raise the temperature to the substance’s ignition point. Spontaneous heating occurs when the temperature of a given substance rises without any external heat source present. Heat is given off by oxidation, but in most circumstances it dissipates harmlessly. However, if three conditions are present, spontaneous heating can lead to ignition:  The material in question insulates more heat than is being dissipated  Heat production is great enough to reach the ignition temperature  Enough air is present to support combustion Examples of such circumstances are bunched-up oily rags and charcoal piles. Hypergolic mixtures are normally fuels used to propel missiles or rockets. These liquids are designed to ignite once in contact with another hypergolic mixture and do not require an external ignition source. Friction sparks are created when two hard surfaces touch one another with sufficient force. One of the surfaces is usually metal. These sparks can ignite any flammable gases and vapours present. Sources of Heat As the temperature of a substance rises, the motion of the molecules increases and becomes more rapid. Heat, as energy, is a measure of molecular motion in a material. Because molecules are constantly moving, all matter contains some heat regardless of how low the temperature is. The speed of the molecules increases when a body of matter is heated. Anything that sets the molecules of a substance in motion produces heat in that material. The sources of heat energy generally encountered in mine rescue are:  Chemical heat energy  Electrical heat energy  Mechanical heat energy Chemical heat energy is generated when combustible material absorbs heat from a source of ignition. It is the most common source of heat energy in combustion. Electrical energy can lead to combustion by releasing heat through arcing, induction, or resistance to the flow of an electrical current. Static electricity can also produce a spark that is capable of igniting flammable vapours and gases. Mechanical heat energy is produced by either compression or friction. Two materials moving against one another create friction, which releases heat and/or sparks. Compression creates heat when pressurizing gas in a container. 10-7 Transmission of Heat Heat can travel throughout a burning building by one or more of three methods: conduction, convection, and radiation. Heat tends to move from a hot substance to a cold substance. Conduction involves transfer of heat from one body to another by direct contact or by an intervening heat-conduction medium. Speed of transfer is dependent on the conductivity of the material. Good heat conductors include copper, aluminum, and iron. Poor heat conductors include masonry, wood, fibrous materials, and air, liquids, and gases. Convection is the transfer of heat by the movement of air or liquid. When liquids and gases are heated they begin to move within themselves. As heated air expands and rises, cooler air takes its place at the lower levels. Convection heat currents are generally the cause of heat movement from floor to floor, from room to room, and from area to area. The spread of fire by convection influences the positions for fire attack and ventilation more than any other method of heat transmission. Radiation is the transmission of energy as an electromagnetic wave without an intervening medium. Heat waves (infrared rays) are similar to light waves in nature but they differ in length and energy. As an object is exposed to radiant heat waves, it will absorb or reflect the heat depending on its properties. Radiated heat is one of the major sources of fire spread and its importance demands an immediate defensive attack at points where radiation exposure is severe. Products of Combustion When a fuel burns there are three products of combustion: 1. Thermal Energy is released as heat and flame. 2. Smoke (Particulate) is solid matter made up of unburned, partially, and completely burned substances. 3. Toxic Smoke (fire gases) is made up of the various gases produced during the combustion process. A few examples are carbon monoxide, hydrogen cyanide, and chlorine. 10-8 CLASSIFICATION OF FIRES Fires are classified into five categories of fire based on important properties, such as the materials combusting and the means of extinguishment. Identifying the correct class of fire is integral to any firefighting response. Class “A” - Fires involve ordinary combustible materials, such as paper, wood, and cloth. These fires require a cooling, blanketing, or wetting extinguishing agent such as water or multi-purpose dry chemical. Class “B” – Fires involve flammable liquids such as gasoline, kerosene and greases. Extinguishing agents for this type of fire include carbon dioxide, dry chemical and foam that can interrupt the chemical chain reaction, exclude oxygen, and inhibit the release of combustible vapours. Class “C” – Fires involve energized electrical equipment. A typical extinguishing agent is carbon dioxide. High value areas are protected with “clean agents” that leave no residue on electrical equipment. If the electricity can be de-energized (turned off), the underlying fuel is often class A or B. Class “D” - Fires involve combustible metals such as magnesium, potassium, lithium, titanium, and aluminum. Special dry powder extinguishing agents are required for this class of fire, and must be designed for the specific hazardous metal. If not available, dry sand can be used. Do not use water. Class “K” - Fires involve commercial kitchen appliances with vegetable oils, animal oils, or fats at high temperatures. A wet potassium acetate, low pHbased extinguishing agent is used for this class of fire. 10-9 PHASES OF FIRE When fire is confined to a building or room, a situation develops that requires carefully calculated and executed ventilation procedure to prevent further damage and reduce danger. This type of fire can be best understood by an investigation of its four progressive phases:  Incipient  Growth  Fully Developed  Decay Incipient (Ignition) Phase The incipient phase starts when the elements of the fire tetrahedron come together and combustion begins. The oxygen content in the air has not been significantly reduced and the fire is producing some gases. The temperature in the room during this phase will only be slightly increased. Growth Phase During the growth phase, oxygen-rich air is drawn into the flame as convection (the rise of heated gases) carries the heat to the uppermost regions of the confinement area. The heated gases spread out laterally from the top downward, forcing the cooler air to seek lower levels and eventually igniting all the combustible material in the upper levels of the room. This process is known as thermal layering. Additional fuel is ignited and the fire grows in size. Flashover can occur spontaneously and rapidly with a release of dangerous amounts of heat and into the next phase of the fire. Fully Developed Phase During the fully developed phase, oxygen is consumed rapidly and the heat produced is at its maximum. All combustible materials in the compartment are burning and producing large volumes of fire gases. The fire will continue to burn as long as fuel and oxygen remain. 10-10 Decay Phase In the decay phase, flame may cease to exist and the fuel and/or oxygen are nearly exhausted. Burning is reduced to glowing embers. The fire will continue to smoulder and the room will completely fill with dense smoke and gases of combustion. Eventually the fire will go out. HAZARDS OF FIRE DEVELOPMENT Rollover occurs when unburned combustible gases that were released during the ignition or growth phase of a fire accumulate at the ceiling. When they mix with oxygen and reach their flammable range, they ignite and a fire front (licks of flame igniting in upper layers of smoke) develops, expanding very rapidly and rolling across the ceiling. Flashover is the transition from the growth phase to the fully developed phase of a fire. It occurs when the surfaces and contents involved in the fire have been heated and gases given off by pyrolysis have ignited. Flame breaks out almost at once over the surface of the contents involved in the space. Signs of flashover are:  Dense black smoke  Fire gases begin to fill the fire area  Rollover is visible 10-11 Backdraft usually occurs during the decay phase when a fire is smouldering. If there is insufficient oxygen, the unburned gases may collect in pockets throughout the structure or fill the entire building. Such a condition needs only the admission of sufficient fresh air (oxygen) to cause a very rapid burning of these gases, the expansion of which may be sufficient to cause an explosion. The degree of intensity of the back draft depends upon the degree of confinement, the amount of heated gases, and the rate and volume of fresh air (oxygen) admitted. This type of condition can be made less dangerous by proper ventilation. Signs of impending backdraft:  Little or no visible flame  Smoke emanating under pressure from cracks, i.e., around windows or doors  Smoke may be drawn back in  Smoke is exiting in puffs or intervals  Black smoke becoming dense grey yellow  Smoke-stained or blackened windows 10-12 Thermal Layering is caused by convection and is the tendency for gases to form into layers according to their temperatures. It is also known as heat stratification or heat balance. The hottest gases tend to accumulate at upper levels, a phenomenon known as mushrooming. Cooler gases accumulate at lower levels. Thermal layering is disrupted when water is applied directly into the layer without proper ventilation. This results in steam, smoke, higher temperatures and decreased visibility at the lower level which are detrimental to a rescuer. FIRE EXTINGUISHERS Fire Extinguisher Classification Fire extinguisher classification is based on physical fire extinguishing potential. Extinguishers are designated as Class “A”, Class “B”, Class “C”, Class “D”, and Class “K”, with some types having a dual or triple classification. The classification consists of a number and a letter. It appears on the label affixed to the appliance by the Underwriters’ Laboratories of Canada (ULC) or another recognized agency. The numeral indicates the approximate relative fire extinguishing potential of the extinguisher. In addition, it is an approximation of the number of square feet (1ft² = 0.09 m²) of appreciable depth flammable liquid that may be extinguished. Appreciable depth is defined as a depth of liquid greater than ¼ inch (6 mm). The letter refers to the class of fire. The number indicates “units” of fire extinguishing potential and does not refer to the size, capacity or quantity of extinguishing agent used. These ratings are based on an untrained operator. An expert can be expected to extinguish up to 2.5 times as much fire as a novice with the same quantity of agent. 1A = agent contained is equivalent to 1.25 U.S. gallons (4.7 L) of water B = rated to extinguish the square footage of Class B fire C = non-conductive agent Examples:  4A 60B C = agent contained is equivalent to 5 U.S. gallons (18.8 L) of water, rated to extinguish 60 ft² (5.6 m2) of Class B fire. Agent is non-conductive.  10A 80B C = agent contained is equivalent to 12.5 U.S. gallons (47 L) of water, rated to extinguish 80 ft2 (7.4 m2) of a Class B fire. Agent is non-conductive. 10-13 Types of Fire Extinguishers Note: Operating instructions must be clearly understood. Extinguishers must be fully charged, in their designated place, and ready for use. Hand-Operated Pump Normally used for water-type agents only. It has a built-in hand-operated double-action pump that discharges water on a continuous up/down or in/out stroke. These extinguishers are normally rated Class “A” only. Stored pressure The expellant and the extinguishing agent are stored within a single cylindrical container. extinguisher will include:  Pressure gauge  Carrying handle  Discharge lever with pin/tamper seal  May or may not have a hose The This type of extinguisher can contain most agents including:  Water  AFFF  Dry powder  Dry chemical (including multipurpose) These extinguishers may be rated for a combination of Class “A”, “B” and/or “C” fires as well as Class “D”. Check the label. Gas Cartridge The expellant is contained in a separate cartridge. This cartridge is normally attached to the outside of the cylinder but it can also be found inside with the agent. This type of extinguisher primarily contains:  Dry powder  Dry chemical (including multipurpose) These extinguishers can be rated for Class “A”, “B”, “C”, “D” fires, or a combination thereof. 10-14 Self-Expellant In this type the expellant is the extinguishing agent. The agent has enough vapour pressure to expel themselves when the extinguisher is activated. These extinguishers can be rated for Class “A”, “B”, “C”, “D” fires, or a combination thereof. Large Wheeled and Stationary Units These units are located by fire protection specialists to cover specific risks in most cases, such as fuel and lube stations. These extinguishers can be rated for Class “A”, “B”, “C”, “D” fires, or a combination thereof. 10-15 Extinguishing Agents Mine rescuers must be familiar with the different extinguishing agents available and the corresponding classes of fire. Extinguishing Agent Water Classes A Advantages      Carbon Dioxide B, C   Non-toxic, plentiful, efficient Converts from liquid to steam, absorbing heat in the process Can be pressurized Good range and penetration Absorbs more heat per volume than any other agent Does not leave a residue Non-freezing Limitations       Limited range Affected by the wind Can be hazardous if used in a confined or unventilated space Cold shock to electrical equipment Leaves a residue Can be corrosive Limited range Limited cooling effect  Non-freezing Can be used with water stream or fog Can be used in the wind     Multi-Purpose Dry A, B, C Chemical  Non-freezing Foam A, B (Two classes: Class A and B)  Class A foam has excellent wetting and penetrating properties due to low surface tension Class B foam can make water float on fuels that are lighter than water Class A/B create a vapour seal on fuels       Leaves a residue Limited range Limited cooling effect Leaves a residue Will freeze Requires selection of correct foam for the fire application  Incorrect application can spread the fire Not widely available Specific to only one type of metal Only rated for Class K fires Dry Chemical B, C (standard ordinary base)   Generally safe for only Class A fires Electrically conductive   Dry Powder D  Specific agents used for Class D fires   Wet Agents K    Saponification turns oils and fats into soap/foam Creates thick blanket to smother the fire Effective, easy to clean up  10-16 Portable Fire Extinguishers The basic components of portable fire extinguishers are:  Cylinder or Container: Holds the extinguishing agent. Some extinguishers also contain expellant, which can be stored internally (stored pressure) or externally (cartridge type).  Handle: Used to carry an extinguisher and to be held during use.  Nozzle/Horn: Expels agent. Attached to the valve assembly or at the end of a hose.  Activation Mechanisms: Discharges agent when activated.  Locking Mechanism/Tamper Seal/Pin: Prevents accidental discharge.  Pressure Indicator: On stored-pressure extinguishers, the gauge shows pressure of extinguishing agent stored. Some cartridge extinguishers have a pin that indicates whether it has been pressurized. Other extinguishers may not have any indicator.  Label: Indicates classification, agent, as well as maintenance and use instructions. VENTILATION Ventilation is an important firefighting tactic that involves the expulsion of heat, gases, and smoke from a fire building, permitting the mine rescuers to safely find trapped individuals and attack the fire. If not properly ventilated (e.g., poorly timed or located), a fire can:  Be much harder to control  Produce enough heat to create a flashover  Result in conditions conducive to backdrafts  Increase the fire’s air supply, causing it to grow and spread rapidly. Natural  Open doors/windows, wind, etc.  Can be vertical or horizontal Mechanical  Positive Pressure Ventilation (PPV) – PPV fans  Negative Pressure Ventilation (NPV) – Smoke ejectors Hydraulic Water fog spray – Nozzle at 60 degree fog pattern covering 90% of an opening Advantages of ventilation  Aids life-saving and rescue  Speeds attack and extinguishment  Controls fire spread  Reduces danger of backdraft  Reduces mushrooming  Reduces hazard to rescuers  Permits prompt salvage operations by reducing smoke, heat, water, and fire damage Considerations for Safely Performing Ventilation  Location, duration, and extent of fire  The age and type of structure involved  Escape routes for rescuers and casualties    Need, type, and location of ventilation Whether ventilation can be performed safely Trained personnel, tools, and equipment available 10-17 EQUIPMENT FIRES Mine rescuers should not attempt to fight equipment fires unless they can do so competently and have the necessary equipment. Mine rescuers must be aware of the numerous hazards present in equipment fires. These include but are not limited to:  Fuel and lubricant volumes  Batteries and electrical  Stored energies, e.g., hydraulic components, airbags, and tires  Unidentified cargo BLEVE (BOILING LIQUID EXPANDING VAPOUR EXPLOSION) The information contained within this section in no way prepares the rescuer to actively respond to potential BLEVEs. Always operate within your scope. A confined gas or liquid is potentially dangerous, regardless of whether the content is flammable. BLEVEs can be caused by a fire near or impinging the storage vessel, heating the contents and increasing the pressure inside. Storage vessels are designed to withstand the stored pressure, but impinging flame can cause the metal to weaken and eventually fail. If the storage vessel is being heated in an area where there is no liquid, it may rupture faster without the liquid to absorb the heat. Pressurized vessels are equipped with relief valves that vent off excess pressure, but the vessel can still fail if the pressure is not released quickly enough. Relief valves are sized to release pressure fast enough to prevent the pressure from increasing beyond the strength of the vessel, but not so fast as to be the cause of an explosion. An appropriately sized relief valve will allow the liquid inside to boil slowly, maintaining a constant pressure in the vessel until all the liquid has boiled and the vessel empties. If the substance being stored is flammable, once the vessel fails the liquid immediately turns into a rapidly expanding cloud of vapour that ignites into a huge fireball. Mine rescuers must keep in mind that a BLEVE can send solid projectiles flying for great distances. 10-18