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Labws 5C - Coggle Diagram

- - - - splashes flammable liquid, spreads fire instead
    - - ● Rate of heat generation is faster than rate of heat removal --cannot use water to reduce temp. to below ignition temp.
      - ● Water expand 1700x as vapor ; it can cause explosion if vaporised too fast
- - - - Liquids: Petrol, LPG, gasoline, acetone (C3H6O), pentane (C5H12)
      - Solids: Plastics, wood dust, fibers, metal particles, living tissues
      - Gases: Acetylene (C2H2), propane (C3H8), carbon monoxide (CO), hydrogen (H2)
    - - air (containing 21% O2).
        
        Other oxidising agents
        
        Liquids Hydrogen peroxide (H2O2), nitric acid (HNO3), perchloric acid (HClO4)
        
        Solids Metals peroxides, ammonium nitrite (NH4NO3)
        
        Gases Air (21% O2), oxygen, fluorine, chlorine
    - - Auto-ignition temperature (AIT) is the lowest temperature that the substance will ignite (due to the heat from the surrounding) even if ignition source is absent
      - Sources of ignition includes electric sparks, smoking hot surfaces, static discharge
      - heat from the fire will maintain the temperature
- - - - a) Water
        
        a)Hose delivery (a solid stream or a spray).
        b) Sprinkler system. c) Hose reel. d) Water bucket system.
        
        reduces temp to below ignition temp
        
        water extinguish fire through cooling and smothering
        
        Advantages and Disadvantages
        
        Advantages of water :
        
        a) At room temp., water is heavy and stable liquid.
        
        c) High latent heat of vaporization
        
        d) Boiled into steam, its volume increases. displaces air around the fire and reduce the O2 available for combustion.
        
        e) Cheap
        
        f) Easily available
        
        con't
        
        g)Very effective on substance that have specific gravity higher than H2O
        
        2 more items...
        
        b) high specific heat capacity
        
        Disadvantages
        
        a) Conductive ,electrical shock can occur.
        
        3 more items...
      - b) Carbon Dioxide
        
        How it stops the fire
        
        1) CO2 is used for flammable liquids, gas /electrical fire and even on ordinary combustible such as paper and clothes.
        
        breaking fire triangle
        
        2) CO2 function by : • reducing O2 content by dilution or displacement to a point where it cannot sustain combustion.
        
        Advantages and disadvantages
        
        Advantages of CO2 :
        
        a) Non-combustible.
        
        b) Non-conductive.
        
        c) Not reactive to most substance.
        
        f) As a gas, it can penetrate and spread to all fire area.
        
        d) non-toxic nor corrosive
        
        e)no residue
        
        g)easily liquified and bottled under pressure
        
        h) stable even after being stored for a long time
        
        i)provide cooling effect
        
        Disadvantages
        
        a) Low cooling capacity and short period of extinguishing atmosphere.
        
        b) For deep fire, a high concentration of CO2 and a longer holding time are required.
        
        d) Cannot be used in area with high human density unless evacuation is done before discharge of CO2.
        
        c)CO2 is not visible, leaks can result in asphyxiating(deprivation of air) environment
        
        e)ineffective against large area of fire
        
        f) cause freezing which damages materials
        
        heavy, sit on the fire for a longer period of time
      - c) Powder (dry agents)
        
        Dry powders are small particles of inert chemicals.
        
        They formed a physical barrier to reduce the O2 to the fire.
        
        Moreover, a crust will be formed over the burning material by the action of heat on the powder.( Heat trapped within crust)
        
        Advantages and Disadvantages
        
        Advantages of powder :
        
        4 more items...
        
        Disadvantages
        
        a) Messy and not suitable for electronic equipment.
        b) Inhaling the powders may cause health problems.
- - - - Ventilation: Good ventilation will rapidly disperse vapours given off from spill, leak, or release from any process.
      - reduces vap. conc. from reaching the explosive range
      - C
        
        Containment
        
        Suitably contained the flammable substances or its spill. Use of lidded containers and spillage catchments trays can help to prevent spillages spreading, limit fire to a certain area
        
        Secondary containment
      - E
        
        Exchange
        
        Exchange for a less flammable one.
        
        Eliminate from the process altogether.
        
        Consider other ways of carrying out the job more safely. e.g use steam to heat up the process
      - S
        
        Separation
        
        Stored and use flammable substance away from other processes and general storage areas with flammable substances.
        
        Separate the flammable substance or process by a physical barrier, wall or partition. Eg. flame-proof cabinet fitted with ventilation, spillage sump at bottom of cabinet-separate flammable materials from non-flammable materials
      - Ignition
        
        Ignition
        Remove all ignition sources from the storage and handling areas.
        Ignition sources can be sparks (electrical equipment or welding and cutting tools), hot surfaces, open flames from heating equipment, smoking materials etc.