PSMZA Course Note (Chapter 2)

2.0 AND PREVENTION SYSTEM Fire is the rapid oxidation of a material in the exothermic chemical process of combustion, releasing heat, light, and various reaction products. Slower oxidative processes like rusting or digestion are not included by this definition.

The flame is the visible portion of the fire. If hot enough, the gases may become ionized to produce plasma. Depending on the substances alight, and any impurities outside, the color of the flame and the fire's intensity will be different.

Fire in its most common foam can result in conflagration, which has the potential to cause physical damage through burning. Fire is an important process that affects ecological systems across the globe. The positive effects of fire include stimulating growth and maintaining various ecological systems. Fire has been used by humans for cooking, generating heat, signaling, and propulsion purposes. The negative effects of fire include water contamination, soil erosion, atmospheric pollution and hazard to life and property.

2.1 Source of Fire The fire triangle or combustion triangle is a simple model for understanding the necessary ingredients for most fires. The triangle illustrates the three elements a fire needs to ignite: heat, fuel, and an oxidizing agent (usually oxygen). A fire naturally occurs when the elements are present and combined in the right mixture, and a fire can be prevented or extinguished by removing any one of the elements in the fire triangle. For example, covering a fire with a removes the "oxygen" part of the triangle and can extinguish a fire.

Figure 2.1: Fire triangle Figure 2.2: Fire tetrahedron

Fires start when a flammable a combustible material, in combination with a sufficient quantity of an oxidizer such as oxygen gas or another oxygen-rich compound, is exposed to a source of heat or ambient temperature above the flash point for the fuel mix, and is able to sustain a rate of rapid oxidation that produces a chain reaction. This is commonly called the fire tetrahedron.

Fire cannot exist without all of these elements in place and in the right proportions. For example, a flammable liquid will start burning only if the fuel and oxygen are in the right proportions. Some fuel-oxygen mixes may require a catalyst, a substance that is not directly involved in any chemical reaction during combustion, but which enables the reactants to combust more readily.

Once ignited, a chain reaction must take place whereby fires can sustain their own heat by the further release of heat energy in the process of combustion and may propagate, provided there is a continuous supply of an oxidizer and fuel.

If the oxidizer is oxygen from the surrounding air, the presence of a force of gravity, or of some similar force caused by acceleration, is necessary to produce convection, which removes combustion products and brings a supply of oxygen to the fire. Without gravity, a fire rapidly surrounds itself with its own combustion products and non-oxidizing gases from the air, which exclude oxygen and extinguish it. Because of this, the risk of fire in a spacecraft is

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small when it is coasting in inertial flight. Of course, this does not apply if oxygen is supplied to the fire by some process other than thermal convection.

Fire can be extinguished by removing any one of the elements of the fire tetrahedron. Consider a natural gas flame, such as from a stovetop burner. The fire can be extinguished by any of the following: i. Turning off the gas supply, which removes the fuel source. ii. Covering the flame completely, which smothers the flame as the combustion both uses the available oxidizer (the oxygen in the air) and displaces it from the area around the flame with CO2. iii. Application of water, which removes heat from the fire faster than the fire can produce it. iv. Application of a retardant chemical such as Halon to the flame, which retards the chemical reaction itself until the rate of combustion is too slow to maintain the chain reaction.

2.1.1 Stages of Fire Development

i. Pre-flashover Stage Fire remains limited in size initially, and can be easily extinguished using a portable at first. Detection may not occur until flames become visible or when heat is produced.

ii. Flashover Stage Heat becomes intense and high enough to ignite common combustible materials within the room, leading to a fully developed fire. This can happen within minutes of the pre-flashover stage when the proper conditions are in place.

iii. Post-flashover Stage Fully developed phase of a fire, whereby all exposed combustibles in the room are involved. This may result in total loss of collections within the room; the entire building is threatened. Flames may spread to other rooms through hallways and ceiling voids. Fire will eventually burn out when all combustibles are consumed. Because fire can grow and spread rapidly, it is important to detect and extinguish it at the earliest stage possible in order to reduce the risk of serious damage, injury or loss.

Figure 2.3: Fire development stages

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2.1.2 Source of Fire Fuel Anything that burns is fuel for a fire. To look for the things that will burn reasonably easily and are in enough quantity to provide fuel for a fire or cause it to spread to another fuel source.

Some of the most common 'fuels' found in factories and warehouses are: i. Flammable liquid-based products, such as paints and varnishes ii. Flammable chemicals, such as certain cleaning products and photocopier chemicals iii. Flammable gases such as liquefied petroleum gas (LPG) and flammable refrigerants iv. Stored goods and high piled or racked storage v. Foodstuffs containing sugar and oils, such as sugar-coated cereal and butter vi. Plastics and rubber, such as video tapes, polyurethane foam-filled furniture vii. Paper products, such as stationery, advertising material and decorations; viii. Packaging materials ix. Plastic and timber storage aids both in use and idle, such as pallets and palletizers x. Combustible insulation, such as panels constructed with combustible cores; xi. Textiles and soft furnishings, such as hanging curtains and clothing displays xii. Waste products, particularly finely divided items such as shredded paper and wood shavings, offcuts, dust and litter/rubbish.

2.1.3 Source of Fire Ignition/Heat Some typical sources of ignition include: i. Exterior and natural sources such as lightning ii. Electrical sources such as faulty or overloaded wiring, electrical panels, electrical equipment and appliances, and HVAC (heating/ventilation/air conditioning) systems iii. Proximity of combustible materials to a heat source such as portable heaters iv. Open flames such as candles and food warmers used during catered events v. "interpretive fires" such as fireplaces, cook stoves, candles, blacksmith shops vi. Construction and renovation activities such as hot work example welding and paint removal vii. Improper use, storage, and/or disposal of flammable liquids such as paint thinners viii. Smoking materials ix. Gas leaks

2.2 The Spreading of The Fire Most fires start in the contents of a building. But if the flames are not quickly extinguished while in the content phase; they will extend to, and throughout the structure. It spreads throughout concealed spaces, poke through walls, common roof or attic spaces. Sometimes even along the outside of the building. Its cause of heat transfer.

Heat transfer is a major factor in the ignition, growth, spread, decay and extinction of a fire. It is important to note that heat is always transferred from the hotter object to the cooler object - heat energy transferred to and object increases the object's temperature, and heat energy transferred Figure 2.4: Fire spreading from and object decreases the object's temperature

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Fires can spread by four method:

i. Direct ignition The ignition system for the fire combustion creates such as a lightning spark that ignites the fuel. Example of direct ignition was open flames, lightning, lighted cigarette butts and hot ashes.

Figure 2.5: The fire ignition

ii. Radiation Radiation is heat transfer by electromagnetic waves. It is the type of heat one feels when sitting in front of a fireplace or around a campfire. It travels in straight lines at the speed of light. This is the reason that when facing the fire, only the front is warmed. The backside is not warmed until the person turns around. The earth is heated by the sun through radiation. Sunburns are a “fact of life” when people are exposed to the sun very long. Most of the preheating of fuels ahead of a fire is by radiation of heat from the fire. As the fire front gets closer, the amount of radiant heat received is increased.

Figure 2.6: The fire radiation

iii. Convection Convection is heat transfer by the movement of liquids or gasses. Convection is the transfer of heat by the physical movement of hot masses of air. As air is heated, it expands (as do all objects). As it expands, it becomes lighter than the surrounding air and it rises. This is why the air near the ceiling of a heated room is warmer than that near the floor. The cooler air rushes in from the sides. It is heated in turn and it also rises. Soon a convection column is foamed above the fire which can be seen by the smoke that is carried aloft in it. This “in-draft” of cooler air from the side helps to supply additional oxygen for the combustion process to continue.

Figure 2.7: The fire convection

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iv. Conduction Conduction is heat transfer within solids material or between contacting solids. Most metals are good heat conductors. Wood is a very poor conductor so it transmits heat very slowly. This can be illustrated by the fact that a wooden handle on a hot frying pan remains cool enough to be held by the bare hands. Conduction is not an important factor in the spread of forest fires. Example situation of that were heating elements, hot metals

Figure 2.8: The fire conduction

2.2.1 The Basic Concept of Fire Control The triangle illustrates the three elements a fire needs to ignite: heat, fuel, and an oxidizing agent (usually oxygen). A fire naturally occurs when the elements are present and combined in the right mixture and a fire can be prevented or extinguished by removing any one of the elements in the fire triangle.

To stop a combustion reaction, one of the three elements of the fire-triangle has to be removed. There are a few basic concepts used for fire control, it’s: i. Removing Heat Heat can be removed by the application of a substance which reduces the amount of heat available to the fire reaction. This is often water, which requires heat for phase change from water to steam. Introducing sufficient quantities and types of powder or gas in the flame reduces the amount of heat available for the fire reaction in the same manner. Scraping embers from a burning structure also removes the heat source. Water can be used to lower the temperature of the fuel below the ignition point or to remove or disperse the fuel.

ii. Removing Fuel Without fuel, a fire will stop. Fuel can be removed naturally, as where the fire has consumed all the burnable fuel, or manually, by mechanically or chemically removing the fuel from the fire. Fuel separation is an important factor in fire suppression, and is the basis for most major tactics, such as controlled burns. The fire stops because a lower concentration of fuel vapor in the flame leads to a decrease in energy release and a lower temperature. Removing the fuel thereby decreases the heat.

iii. Reducing Oxygen Without sufficient oxygen, a fire cannot begin, and it cannot continue. With a decreased oxygen concentration, the combustion process slows. Oxygen can be denied to a fire using a carbon dioxide fire extinguisher or a fire blanket. For example, covering a fire with a fire blanket removes the "oxygen" part of the triangle and can extinguish a fire.

iv. Cut-off The Chain Reaction The fire tetrahedron represents the addition of a component, the chemical chain reaction, to the three already present in the fire triangle. Once a fire has started, the resulting exothermic chain reaction sustains the fire and allows it to continue until or unless at least one of the elements of the fire is blocked. Combustion is the chemical reaction that feeds a fire more heat and allows it to continue. Inert agents must be used to break the chain reaction. In the same way, as soon as one of the four elements of the tetrahedron is removed, combustion stops.

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2.3 Fire Prevention System In A Building The objective of fire prevention system in the building has to take precautions to prevent potentially harmful fires, and be educated about surviving them. It is a proactive method of reducing emergencies and the damage caused by them. There are two types of preventing system, it’s: i. Active ii.

2.3.1 (AFP) Active fire protection (AFP) is an integral part of fire protection. AFP is characterized by items and/or systems, which require a certain amount of motion and response in order to work, contrary to passive fire protection.

There are four categories of AFP, it’s: i. Fire Suppression Fire can be controlled or extinguished, either manually (firefighting) or automatically. Manual includes the use of a fire extinguisher or a standpipe system. Automatic means can include a system, a gaseous clean agent, or firefighting foam system. Automatic suppression systems would usually be found in large commercial kitchens or other high-risk area. Types of fire suppression were: a. Fire Extinguisher b. Flame Extinguisher c. Fire Hydrant d. Fire Hose reel e. Fire Bucket f. Firefighting Foam System g. Standpipe (Dry and Wet) h. Fire Blanket

ii. Sprinkler Systems Fire sprinkler systems are installed in all types of buildings, commercial and residential. They are usually located at ceiling level and are connected to a reliable water source, most commonly city water. A typical sprinkler system operates when heat at the site of a fire causes a glass component in the sprinkler head to fail, thereby releasing the water from the sprinkler head. This means that only the sprinkler head at the fire location operates - not all the sprinklers on a floor or in a building. Sprinkler systems help to reduce the growth of a fire, thereby increasing life safety and limiting structural damage. The types of sprinkler system were: a. Quick Response b. Standard Response c. Control Mode Specific application (CMSA) d. Early Suppression Fast Response (ESFR)

iii. Fire Detection Fire is detected either by locating the smoke, flame or heat, and an alarm is sounded to enable emergency evacuation as well as to dispatch the local fire department. An introduction to fire detection and suppression can be found here. Where a detection system is activated, it can be programmed to carry out other actions. These include de-energizing magnetic hold open devices on fire doors and opening servo-actuated vents in stairways. Types of fire detection were: a. System b. System c. d. Smash Glass

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iv. Hypoxic Air Fire Prevention Fire can be prevented by hypoxic air. Hypoxic air fire prevention systems, also known as oxygen reduction systems are new automatic fire prevention systems that reduce permanently the oxygen concentration inside the protected volumes so that ignition or fire spreading cannot occur. Unlike traditional fire suppression systems that usually extinguish fire after it is detected, hypoxic air is able to prevent fires. a. Carbon Dioxide Gas System

2.3.2 Passive Fire Protection (PFP) Passive fire protection (PFP) is an integral component of the three components of structural fire protection and fire safety in a building. PFP attempts to contain fires or slow the spread, through use of fire-resistant walls, floors, and doors (amongst other examples). PFP systems must comply with the associated Listing and approval use and compliance in order to provide the effectiveness expected by building codes. Examples of PFP component were: i. Fire-Resistance Rated Wall/Door ii. Firewall iii. Fire-resistant glass iv. Fire-resistance rated floors v. Occupancy separations vi. Closures vii. Fire stops viii. Grease ducts ix. Cable coating x. Spray fireproofing xi. Fireproofing xii. Enclosures

2.4 Classes of The Fire In firefighting, fires are identified according to one or more fire classes. Each class designates the fuel involved in the fire, and thus the most appropriate extinguishing agent. The classifications allow selection of extinguishing agents along lines of effectiveness at putting the type of fire out, as well as avoiding unwanted side-effects. For example, non- conductive extinguishing agents are rated for electrical fires, so to avoid electrocuting the firefighter. There are six classes of fire to refer in Asian country, it’s seeing on table 2.1.

Table 2.1: Class and types of fuel source No. Classes Fuel/Heat source 1 A Ordinary combustibles 2 B Flammable liquids 3 C Flammable gases 4 D Combustible metals 5 E Electrical equipment 6 F Cooking oil or fat

2.5 The Fire Extinguisher A fire extinguisher, flame extinguisher, or simply an extinguisher, is an active fire protection device used to extinguish or control small fires, often in emergency situations. It is not intended for use on an out-of-control fire, such as one which has reached the ceiling, endangers the user example no escape route, smoke and explosion hazard or otherwise requires the expertise of a fire department. Typically, a fire extinguisher consists of a hand- held cylindrical pressure vessel containing an agent which can be discharged to extinguish a fire. Portable fire extinguishers apply an extinguishing agent that will cool burning fuel, displace or remove oxygen, or stop the chemical reaction so a fire cannot continue to burn. When the handle of an extinguisher is compressed, agent is expelled out the nozzle. A fire extinguisher works much like a can of hair spray.

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Figure 2.9: The fire extinguisher component and operation

There are two operation types of fire extinguishers: i. Stored pressure ii. Cartridge-operated

2.5.1 Stored Pressure In stored pressure units, the expellant is stored in the same chamber as the firefighting agent itself. Depending on the agent used, different propellants are used. With dry chemical extinguishers, nitrogen is typically used; water and foam extinguishers typically use air. Stored pressure fire extinguishers are the most common type. These extinguishers use compressed carbon dioxide instead of nitrogen, although nitrogen cartridges are used on low temperature (-60 rated) models.

2.5.2 Cartridge-operated Cartridge-operated extinguishers contain the expellant gas in a separate cartridge that is punctured prior to discharge, exposing the propellant to the extinguishing agent. This type is not as common, used primarily in areas such as industrial facilities, where they receive higher-than-average use. They have the advantage of simple and prompt recharge, allowing an operator to discharge the extinguisher, recharge it, and return to the fire in a reasonable amount of time. Cartridge operated extinguishers are available in dry chemical and dry powder types in the U.S. and in water, wetting agent, foam, dry chemical (classes ABC and B.C.), and dry powder (class D) types in the rest of the world.

2.5.3 Types of Agent Fire Extinguishers Handheld extinguishers, which are commonly sold at hardware stores for use in the kitchen or garage, are pressurized with nitrogen or carbon dioxide (CO2) to propel a stream of fire-squelching agent to the fire. The active material may be a powder such as potassium bicarbonate (KHCO3), liquid water, an evaporating fluorocarbon or the propelling agent itself.

Different types of fire extinguishers are designed to fight different types of fire. The three most common types of fire extinguishers are: air pressurized water, CO2 (carbon dioxide), and dry chemical. It’s is:

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i. Water Fire Extinguisher APW (Air pressurized water) cools burning material by absorbing heat from burning material. Effective on class A fires, it has the advantage of being inexpensive, harmless, and relatively easy to clean up. APW units contain from 6 to 9 liters of water in a tall, stainless steel cylinder. Water mist uses a fine misting nozzle to break up a stream of deionized water to the point of not conducting electricity back to the operator. Class A and C rated. It is used widely in hospitals for the reason that, unlike other clean-agent suppressants, it is harmless and non-contaminant.

ii. Foam Fire Extinguisher Applied to fuel fires as either an aspirated (mixed & expanded with air in a branch pipe) or non-aspirated foam to foam a frothy blanket or seal over the fuel, preventing oxygen reaching it. Unlike powder, foam can be used to progressively extinguish fires without flashback. More expensive than water, but more versatile. Use for class A and B fires. Foam spray extinguishers are not recommended for fires involving electricity, but are safer than water if inadvertently sprayed onto live electrical apparatus. There are four types of foam used:

a. Aqueous Film Foaming Foam (AFFF) Used on A and B fires and for vapor suppression. The most common type in portable foam extinguishers. It contains fluoro tensides which can be accumulated in the human body. The long-term effects of this on the human body and environment are unclear at this time.

b. Alcohol-resistant Aqueous Film Foaming Foam ( AR-AFFF) Used on fuel fires containing alcohol. Foams a membrane between the fuel and the foam preventing the alcohol from breaking down the foam blanket.

c. Film Foaming Fluoro Protein (FFFP) Contains naturally occurring proteins from animal by-products and synthetic film- foaming agents to create a foam blanket that is more heat resistant than the strictly synthetic AFFF foams. FFFP works well on alcohol-based liquids and is used widely in motorsports.

d. Compressed Air Foam System (CAFS) Extinguisher that is charged with a foam solution and pressurized with compressed air. Generally used to extend a water supply in wild land operations. Used on class A fires and with very dry foam on class B for vapor suppression.

iii. Dry Powder Fire Extinguisher This is a powder based agent that extinguishes by separating the four parts of the fire tetrahedron. It prevents the chemical reactions involving heat, fuel, and oxygen and halts the production of fire sustaining "free-radicals", thus extinguishing the fire. There are seven types or dry powder agent:

a. Mono-ammonium Phosphate Also known as "tri-class", "multipurpose" or "ABC" dry chemical, used on class A, B, and C fires. It receives its class A rating from the agent's ability to melt and flow at 177 °C (350 °F) to smother the fire. More corrosive than other dry chemical agents. Pale yellow in color.

b. Sodium Bicarbonate "regular" or "ordinary" used on class B and C fires, was the first of the dry chemical agents developed. In the heat of a fire, it releases a cloud of carbon dioxide that smothers the fire. That is, the gas drives oxygen away from the fire, thus stopping the chemical reaction. This agent is not generally effective on class A fires because the agent is expended and the cloud of gas dissipates quickly, and if the fuel is still sufficiently hot, the fire starts up again. While liquid and gas fires don't usually store much heat in their fuel source, solid fires do.

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c. Potassium Bicarbonate (Purple-K) Used on class B and C fires. About two times as effective on class B fires as sodium bicarbonate, it is the preferred dry chemical agent of the oil and gas industry. The only dry chemical agent certified for use in ARFF by the NFPA. Violet in color.

d. Potassium Bicarbonate & Urea Complex (Monnex/Powerex) Used on class B and C fires. More effective than all other powders due to its ability to decrepitate (where the powder breaks up into smaller particles) in the flame zone creating a larger surface area for free radical inhibition. Grey in color.

e. Potassium Chloride or Super-K Dry chemical was developed in an effort to create a high efficiency, protein-foam compatible dry chemical. Developed in the 60s, prior to Purple-K, it was never as popular as other agents since, being a salt, it was quite corrosive. For B and C fires, white in color.

f. Foam-Compatible Which is a sodium bicarbonate (BC) based dry chemical, was developed for use with protein foams for fighting class B fires. Most dry chemicals contain metal stearates to waterproof them, but these will tend to destroy the foam blanket created by protein (animal) based foams. Foam compatible type uses silicone as a waterproofing agent, which does not harm foam. Effectiveness is identical to regular dry chemical, and it is light green in color. This agent is generally no longer used since most modern dry chemicals are considered compatible with synthetic foams such as AFFF.

g. MET-L-KYL / PYROKYL Specialty variation of sodium bicarbonate for fighting pyrophoric liquid fires (ignite on contact with air). In addition to sodium bicarbonate, it also contains silica gel particles. The sodium bicarbonate interrupts the chain reaction of the fuel and the silica soaks up any unburned fuel, preventing contact with air. It is effective on other class B fuels as well. Blue/Red in color.

iv. Carbon Dioxide (CO2) Fire Extinguisher A clean gaseous agent which displaces oxygen. Not intended for class A fires, as the high-pressure cloud of gas can scatter burning materials. CO2 is not suitable for use on fires containing their own oxygen source, metals or cooking media. Although it can be rather successful on a person on fire, its use should be avoided where possible as it can cause frostbite and is dangerous to use as it may displace the oxygen needed for breathing, causing suffocation.

The following table provides information regarding the type of fire and which fire extinguisher should be used.

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