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Chapter 11

Chapter 11






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    Chapter 11 Chapter 11 Presentation Transcript

    • Portable Fire Extinguishers Chapter 11
    • Learning Objectives
      • Discuss the fire extinguisher classification system
      • Discuss the fire extinguisher rating system and to which classification of extinguishers it applies
      • Explain why a certain extinguisher classification requires a conductivity test
      • Explain the acronym PASS in relation to fire extinguisher operation
    • Learning Objectives (continued)
      • Describe the different types of fire extinguishers and their operation
      • List the different extinguishing agents and their applications
      • Discuss the inspection, testing, and maintenance procedures for portable fire extinguishers
    • Introduction
      • Portable fire extinguishers are intended for use in incipient stage where water is ineffective
        • Useful if there is quick access, the correct type is available, and person is trained
        • Has fixed amount of suppression agent
        • Are clearly labeled and require little training
      • Rapid access to the extinguisher is critical
    • Requirements for Fire Extinguishers
      • Code requirements exist in all of the model codes for fire extinguishers
        • Requirements center on use and occupancy conditions and processes
      • IFC requires extinguishers installed in almost every new and existing occupancy classification
      • NFPA 10 lists the requirements for fire extinguishers
    • Fire Extinguisher Classification
      • Through the classification system, extinguishing agents matched to fire hazards
      • Classification designated with letters
        • Class A fires: ordinary combustibles
        • Class B fires. flammable and combustible liquids and gases
        • Class C fires: energized electrical equipment
        • Class D fires: combustible metals
        • Class K fires: cooking media
    • Fire Extinguisher Ratings
      • Class A and B have a number rating to indicate performance capability of the extinguisher
        • Expresses how much fire the extinguisher can handle
      • Class A extinguishers are tested using a wood crib on fire, allowing it to burn for a time
      • Class B extinguishers are tested with a flammable liquid fire in a pan
        • Flammable liquid is usually heptane
      • Class C extinguishers do not receive a rating
    • Figure 11-1 Wood cribbing for Class A extinguisher test
    • Figure 11-3 Class C test for conductivity
    • Types of Fire Extinguishers
      • Pumped, stored pressure, and cartridge pressure categories
      • Many suppression agents:
        • Water, foam, carbon dioxide, dry chemical, wet chemical, dry powder, halon, clean agents
      • Some agents will not work well with a particular category of extinguisher
    • Pump Extinguishers
      • Require manual operation of a pump mechanism
        • Creates pressure in the tank to expel extinguishing agent
      • Extinguishing agent is either water or antifreeze solution
      • Easy to operate and fill
      • Backpack type extinguisher has external pump
        • Mechanism similar to hand-held
    • Stored Pressure Extinguishers
      • Mix pressurized gas and extinguishing agent in the same tank
      • Gas is above the agent and keeps constant pressure on the agent
      • When operated, the pressure of the gas forces the extinguishing agent out of the tank
      • Air or nitrogen frequently used as expelling gas
      • Pressure gauge indicates if pressure is sufficient
    • Cartridge Pressure Extinguishers
      • Similar to stored pressure type, but pressurized gas is in a separate cartridge
        • Attached to the side of the extinguishing tank
      • Activating the extinguisher punctures the cartridge that expels the gas into the tank
      • Allows for easy maintenance of certain types of agents
        • Top removes without dumping the agent or losing the gas pressure
      • Good for agents that settle and need stirring
    • Common Fire Extinguisher Agents
      • Same agents used in sprinkler and suppression systems are common in fire extinguishers
        • Present in smaller amounts
    • Water
      • One of the best agents because it absorbs more heat per pound than any other material
      • Most effective on Class A fires
      • Not effective on some fuels; dangerous to use on others
      • When used in an extinguisher, extinguisher must not be exposed to cold
    • Foam
      • Good agent for Class A but better for Class B fires
      • Foam forms a vapor barrier between the fuel and the atmosphere
      • Agent must discharge through special aspirating nozzle so that air can mix with the agent
      • Two types of foam:
        • Aqueous film-forming foam
        • Film-forming fluoroprotein
    • Carbon Dioxide
      • Carbon dioxide gas effective in Class B and C fires; limited use on Class A fires
      • In extinguisher tank, carbon dioxide is a high-pressure liquid state
        • Expands to a gas when released
      • Depletes the oxygen supply
      • Must be discharged at close range to the fire because air movement carries the gas away
      • Operator must have oxygen supply available to avoid asphyxiation
    • Dry Chemicals
      • Small solid particles propelled by pressurized gas
      • When discharged, chemical smothers the burning material
      • Not considered dangerous or toxic; do not react with flammable liquids or gases; not conductive
      • Once discharged, create a cloud that limits visibility; may cause respiratory problems
      • May leave a corrosive residue
    • Wet Chemicals
      • Wet chemical agents most effective with Class K fires
      • Water-based solutions that mix with potassium carbonate, potassium acetate, potassium citrate
      • React with fat in the cooking medium or food to develop a soapy foam blanket on the surface
        • Smothers, cools, and extinguishes the fire
      • Liquid in the agent cools the cooking media adequately to maintain the foam blanket
    • Dry Powders
      • Class D fires present a challenge
        • Water is not a good choice because it can react with metals to liberate oxygen and fuel the fire
      • Dry powders are one of the most effective agents
        • No one powder effective on all metals
      • Some agents do not work in an extinguisher
        • Applied by shovel, scoop or by hand
    • Halon and Other Clean Agents
      • Halon still in use but less available
        • Gradual fade-out for environmental concerns
      • Leaves no residue; not conductive; more effective than the same amount of CO 2
      • Halons are somewhat toxic and exposure can cause physical problems
        • Vertigo, loss of agility, loss of coordination
      • Two types still in use: 1211, 1301
      • Inert gases generally safe for humans
    • Figure 11-7 Extinguishing agents matched to a fire classification
    • Obsolete Types of Fire Extinguishers
      • Obsolete extinguisher types are not safe to operate and may cause injury
        • Some have corrosive or conductive products
      • Types of extinguishers and products requiring removal from service:
        • Soda acid
        • Chemical foam
        • Vaporizing liquid
        • Cartridge-operated water
    • Obsolete Types of Fire Extinguishers (continued)
        • Cartridge-operated loaded stream
        • Copper or brass shell joined by soft solder on rivets
        • Carbon dioxide extinguishers with metal horns
        • Sold charge-type AFFF extinguishers
        • Pressurized water manufactured prior to 1971
        • Any extinguisher that must be inverted
        • Any stored pressure manufactured before 1955
        • Any extinguishers with 4B, 6B, 8B, 12B, 16B ratings
        • Stored-pressure with fiberglass shells
    • Fire Extinguisher Operation
      • Most portable fire extinguishers operate in a similar manner
      • Some small enough to carry by hand; others have a cart on wheels
      • PASS for hand-held extinguishers
        • Requires little or no training
        • Pictographs depict instructions
      • Any person who might use an extinguisher should know their operation and location
        • Notify other occupants to evacuate
    • Figure 11-10 Portable extinguisher pictograph
    • Portable Fire Extinguisher Inspection, Maintenance, and Testing
      • Inspection, testing, maintenance are the keys to ensuring that extinguishers work
        • Involve a number of different activities that can be conducted by anyone
      • Annual maintenance requires specialized training
      • Hydrostatic testing requires further training
    • Visual Inspections
      • Valuable fire prevention activity
        • General condition of the extinguisher can be determined in a short amount of time
      • Inspections should take place every 30 days
      • Check the location, verify it is of the proper type, check for physical damage, etc.
      • Determine if pressure gauge within normal range
      • Note deficiencies found in prior inspections
    • Maintenance
      • Follow manufacturer’s requirements
        • Involves more thorough inspection
      • Usually yearly, but could be sooner
      • All extinguishers require disassembling and internal examination at regular intervals
        • Look for conditions that could impair the extinguisher
      • Some maintenance activities can be dangerous
        • Personnel require proper training and tools
    • Testing
      • Hydrostatic test critical on all refillable extinguishers
        • Ensure extinguisher will not fail due to unnoticed conditions
      • Test intervals range from five to ten years or on discovery of physical damage or corrosion
      • Typical procedure:
        • Disassemble and fill with water
        • Immerse component in water
        • Pressurize component for desired amount of time
    • Summary
      • Portable fire extinguishers
        • Are intended to suppress small incipient fires
        • Hold a fixed amount of suppression agent, so access should be quick
        • Must have knowledgeable operator
      • Extinguishing agent must be suitable for the type of fire
      • Three categories of extinguishers: pumped, stored-pressure, cartridge pressure