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FIRE & SAFETY - BASIC

FIRE & SAFETY - BASIC. CHEMISTRY OF COMBUSTION. COMBUSTION – Is a very rapid, continuous chemical reaction known as oxidation , which emits heat and light . The three elements needed for combustion are Oxygen Fuel Heat

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FIRE & SAFETY - BASIC

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  1. FIRE & SAFETY - BASIC

  2. CHEMISTRY OF COMBUSTION • COMBUSTION–Is a very rapid, continuous chemical reaction known as oxidation, which emits heat and light. • The three elements needed for combustion are • Oxygen • Fuel • Heat • If they are in the right proportion there is a continuous chemical reaction resulting in FIRE.

  3. The Fire Triangle Fire Safety, at its most basic, is based upon the principle of keeping fuel sources and ignition sources separate.

  4. The Fire Triangle Three elements must be present at the same time to produce fire: • EnoughOXYGENto sustain combustion • EnoughHEATto reach ignition temperature • SomeFUEL or combustible material Together, they produce theCHEMICAL REACTION that is fire Take away any of these elements and the fire will be extinguished

  5. OXYGEN 1. Oxygen does not burn but supports combustion. 2. Fire needs oxygen. 3. Oxygen in atmosphere. 4. Various materials are oxidizers ( give off oxygen when combined with fuels)

  6. HEAT • All fuels give off vapour. • By adding heat to a fuel, vapourization is increased. • The vapour burns and not the fuel. • Heat is obtained from CHEMICAL, ELECTRICAL, MECHANICAL and NUCLEAR ENERGY.

  7. FUEL • Solids – eg. Wood, Plastics • Liquids – eg. Petrol, Diesel • Gas – eg. LPG, LNG …propane, butane, methane.

  8. PRINCIPLES OF EXTINGUISHMENT-to extinguish a flame, one of the components from the triangle of combustion must be removed. BY : • Cooling • Starvation • Smothering • Inhibition of Chain Re-action

  9. COOLING • All elements burn when enough heat is applied. • Our aim is to lower its temperature to below that needed to produce a flame. • Water in various forms is generally used to reduce temperatures of substances

  10. STARVATION Can be achieved by : • Removal of combustibles close to the fire or • Removal of the fire from other combustibles

  11. SMOTHERING - Removal of Oxygen from the fire area or separating it from the fuel: Accomplished by various means eg. Using CO2, Fire-fighting foam, Dry chemical powder

  12. INHIBITION OF CHAIN RE-ACTION • Is used on gas and liquid fires • Uses dry chemical and halogenated hydro-carbons • Interrupts chemical chain re-action (stops flaming )

  13. FUEL CLASSIFICATIONS Fires are classified according to the type of fuel that is burning. If you use the wrong type of fire extinguisher on the wrong class of fire, you might make matters worse. Its very important to understand the five different fire (fuel) classifications…

  14. CLASSES OF FIRE Class A: Wood, paper, cloth, trash, plastics—common solids that are not metals. Class B: Flammable liquids .—gasoline, oil, grease, acetone. . Class C:Gase-Includes flammable gases Class D: Metals—potassium, sodium, aluminum, magnesium. Requires Metal-X, foam, and other special extinguishing agents.

  15. CLASS “A” FIRES WATER– used to reduce the temperature to below its ignition temperature.

  16. CLASS “B” FIRES FOAM, DRY CHEMICAL POWDER OR INERT GAS– used to smother or blanket the surface of the flammable liquid.

  17. CLASS “C” FIRES NON ELECTRICAL CONDUCTIVE EXTINGUISHING AGENTS– used eg. CO2, Halons or Dry Chemical Powder to knockdown or smother the fire. De-energize electricity then fight fire as CLASS “A” or CLASS“B”.

  18. CLASS “D” FIRES SPECIAL DRY POWDER eg. Graphite, Talc or Limestone used to gently cover and smother the fire.

  19. TRANSMISSION OF HEAT • Heat travels from regions of high temperature to regions of low temperature in one of four ways : - conduction - convection - radiation - direct burning

  20. CONDUCTION • The transfer of heat through solids eg. Metals.

  21. CONVECTION The transfer of heat through liquids and gasses. • HOT AIR RISES

  22. RADIATION Transfer of heat through space eg. The sun heats the earth by means of RADIATION

  23. DIRECT BURNING Transfer of heat directly by bringing a flame to a combustible material.

  24. FIRE EXTINGUISHERSFALL INTO TWO CATEGORIES“STORED PRESSURE” and “GAS CARTRIDGE” Most fire extinguishers will have a pictograph label telling you which types of fire the extinguisher is designed to fight. For example, a simple water extinguisher might have a label like this… …which means it should only be used on Class A fires.

  25. STORED PRESSURE VERSUS GAS CARTRIDGE The following slide shows a DRY CHEMICAL TYPE extinguisher in both STORED PRESSURE AND GAS CARTRIDGE

  26. Types of Fire Extinguishers Different types of fire extinguishers are designed to fight different classes of fire. The 4 most common types of fire extinguishers are: • Water • Carbon Dioxide (CO2) • Dry Chemical / Powder • Foam

  27. 1. Water Extinguishers Large red colour coded fire extinguishers that stand about 2 feet tall and weigh about 25 pounds when full. APW stands for “Air-Pressurized Water.” Filled with ordinary tap water and pressurized air, they are essentially large squirt guns.

  28. extinguish fire by taking away the “heat” element of the Fire Triangle. Water Fire Extinguishers

  29. are designed for Class A fires only: Wood, paper, cloth. Water Fire Extinguishers • Using water on a flammable liquid fire could cause the fire to spread. • Using water on an electrical fire increases the risk of electrocution. If you have no choice but to use an APW on an electrical fire, make sure the electrical equipment is un-plugged or de-energized.

  30. 2.Carbon Dioxide Fire Extinguishers The pressure in a CO2 extinguisher is so great, bits of dry ice may shoot out of the horn! CO2 extinguishers are colour coded black. They range in size from 5 lbs to 100 lbs or larger. On larger sizes, the horn will be at the end of a long, flexible hose.

  31. are designed for Class B and C (Flammable Liquids and Electrical Sources)fires only! Carbon Dioxide Fire Extinguishers CO2s will frequently be found in laboratories, mechanical rooms, kitchens, and flammable liquid storage areas. In accordance with FFA CODE regulations (and manufacturers’ recommendations), all CO2 extinguishers Should undergo hydrostatic testing and recharge every 5 years.

  32. Carbon dioxide is a non-flammable gas that takes away the oxygen element of the fire triangle. Without oxygen, there is no fire. Carbon Dioxide Fire Extinguishers CO2 is very cold as it comes out of the extinguisher, so it cools the fuel as well.

  33. May be ineffective in extinguishing a Class A fire because it may not be able to displace enough oxygen to successfully put the fire out. Carbon Dioxide Fire Extinguishers Class A materials may also re-ignite.

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