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  • 1. THE CHEMISTRY OF FIRE
  • 2. Fire Triangle Fires Require Air (oxygen)FuelHeat
  • 3. AirAir is required as a catalystCan be oxygen from the air OR From the Fuel itself
  • 4. Fuel For a fire to start there must besomething to Burn
  • 5. Heat For a Fire to Start,there must be a heat or ignition source
  • 6. TOGETHER, THEY PRODUCE A CHEMICAL CHAIN REACTION THAT IS FIRE, which produces heat and light.
  • 7. Types of FiresFires Are Classifiedby the type FUELthey burn.The 4 Types are A B C D
  • 8. Class A Fires (Carbonaceous) Wood, Paper, Plastic, Rags, etc CombustibleMaterial burn andash is left behind
  • 9. Class B Fires (Oil) Gasoline, Oil, Grease, Paint, etcWater not to be used as oil islighter and will float
  • 10. Class C FiresElectrical Fires and Gases under fire Office Equipment, Motors, Switchgear, Heaters, Gases ELECTRICITY ITSELF DOES NOT BURN.IT PROVIDES THE IGNITION TO START A FIRE
  • 11. Class D Fires Metals Potassium Sodium Aluminum Magnesium
  • 12. PRODUCTS OF FIRE SMOKE HEAT GASES FLAME
  • 13. BY- PRODUCTS OF FIRE1. Smoke • Carbon Di Oxide • Carbon Mono Oxide • Hydrogen Cyanide • Hydrogen Chloride • Unburnt Carbon Particles2. Heat - Burn and other physical effects3. Flames4. Sound5. Pressure • Effect on ears and other limbs}During Explosion
  • 14. TERMS & DIFINITIONS
  • 15. ATOMS AND MOLECULES SMALLEST PART OF A SUBSTANCE WHICH CAN TAKE PART IN A CHEMICAL REACTION IS CALLED AN ATOM SMALLEST PART OS A SUBSTANCE WHICH CAN EXIST FREELY IS CALLED A MOLECULE
  • 16. CHEMICAL REACTIONWHEN TWO OR MORE SUBSTANCES COMBINE TOGETHER TO FORM A NEW SUBSTANCE OR SUBSTANCES, IT IS CALLED A CHEMICAL REACTION
  • 17. EXOTHERM REACTIONA REACTION PRODUCES ENERGY, IEHEAT IS CALLED EXOTHERMREACTIONFIRE IS AN EXOTHERM REATION BETWEENFUEL AND OXYGEN.NEXT TO HEAT, A FIRE GENERALLYPRODUCES LIGHT, COMBUSTION GASES ANDSOOT.
  • 18. ACTIVATION ENERGYTO INITIATE A FIRE A CERTAIN AMOUNT OFENERGY IS NEEDED.TAKE A EXAMPLE OF A SIMPLE TEST WITH GASOLINEAND DIESEL FUEL. A MATCH HAS ENOUGH ENERGY TOLIGHT THE GASOLINE BUT IN THE DIESEL FUEL THEMATCH EXTINGUISHES.IN CHEMISTRY THE ENERGY NEEDED TOSTART A REACTION IS CALLED THEACTIVATION ENERGY.
  • 19. CHAIN REACTIONCHEMICAL REACTIONS NEEDS TO SURMOUNTACTIVATION ENERGY BEFORE THE REACTION CANTAKE PLACE .IN A FIRE, THE INITIAL ENERGY SOURCES THATCAUSE THE FIRE CAN BE MULTIPLE, E.G. A SPARK,AN OPEN FLAME, ELECTRICITY, SUNLIGHT, ETCONCE THE REACTION IS STARTED, HOWEVER, ITGENERATES MORE THAN ENOUGH ENERGY TO BESELF-SUSTAINING, A CHAIN REACTION OCCURS.THE ENERGY GIVEN OFF IN EXCESS CAN BE SEENAS LIGHT AND HEAT GENERATED BY THE FIRE.
  • 20. PYROLYSISTHE ENERGY LIBERATED IN THECOMBUSTION PROCESS CAUSES THECHEMICAL COMPOSITION OF THE FUEL TOBREAK DOWN INTO SMALL MOLECULES THIS PROCESS IS CALLED PYROLYSISTHE PYROLYSIS PROCESS CAUSES THEEVAPORATION OF THE FUEL
  • 21. COMPLETE REACTIONMOLECULES EVAPORATE AND REACT WITHTHE OXYGEN IN THE AIR.COMPLETE COMBUSTION MEANS THATJUST ENOUGH OXYGEN MOLECULESARE PRESENT, TO OXIDISE THE FUELMOLECULES.
  • 22. REACTION SURFACENEXT TO FUEL, OXYGEN AND ENERGY ONESHOULD ALSO NOTE THE MIXING RATIO BETWEENOXYGEN AND FUEL.EXAMPLE, A LOG OF WOOD WILL NOT SUSTAIN AFIRE IF IT IS LIT WITH A MATCH. AN AMOUNT OFWOOD SHAVINGS WILL BECAUSE THIS CAUSES ABETTER MIXTURE BETWEEN FUEL AND AIR,WHICH FAVORS COMBUSTION. LARGER SURFACE OF THE FUEL IN CONTACTWITH THE AIR CAUSES A GREATER REACTIONSURFACE , WHICH FACOURS COMBUSTION
  • 23. INHIBITORIN A FIRE A CHEMICAL CHAIN REACTION OCCURS,RADICALS OF FUEL REACT WITH RADICALS OFOXYGEN HEAT AND COMBUSTION PRODUCTS AREFORMED. ADDING A CHEMICAL MOLECULE, WHICH REACTSWITH THOSE RADICALS WITHOUT SUSTAINING THECOMBUSTION PROCESS CAN STOP THE FIRE. THISCHEMICAL IS CALLED INHIBITORTHIS PRINCIPLE IS USED IN DRY CHEMICALEXTINGUISHERS WICH CONTAIN E.G. POTASSIUM ORSODIUM BICARBONATE OR IN THE NOW BANNEDHALON EXTINGUISHERS
  • 24. CATALYSTCATALYST HAS THE OPPOSITE EFFECT OF ANINHIBITORCATALYST IS A SUBSTANCE, WHICH PROMOTESTHE REACTION (WITHOUT BEING ALTERED ORUSED IN THE REACTION)E.G. ADDING METAL SHAVINGS TO OIL RAGS AIDSTHEIR COMBUSTION
  • 25. IGNITION TEMPERATURETHE IGNITION TEMPERATURE OF ASUBSTANCE (SOLID, LIQUID OR GASEOUS)IS THE MINIMUM TEMPERATURE TO WHICHTHE SUBSTANCE EXPOSED TO AIR MUST BEHEATED IN ORDER TO CAUSE COMBUSTIONOR FIRE
  • 26. FIRE OR FLASH POINTTHE LOWEST TEMPERATURE AT WHICH ASUBSTANCE CONTINUES TO BURN IS(USUALLY A FEW DEGREES ABOVE ITSFLASHPOINT) AND IS CALLED FIRE POINTOR FLASH POINTA SPECIFIC IGNITION TEMPERATURE FOR SOLIDSIS DIFFICULT TO DETERMINE BECAUSE THISEPENDS UPON MULTIPLE ASPECTS SUCH ASHUMIDITY (WET WOOD VERSUS DRY WOOD),COMPOSITION (TREATED OR NON-TREATEDWOOD) AND PHYSICAL FORM
  • 27. AUTO IGNITION TEMPERATURE AUTO-IGNITION TEMPERATURE IS THE LOWESTTEMPERATURE AT WHICH POINT A SOLID, LIQUIDOR GAS WILL SELF-IGNITE WITHOUT AN IGNITIONSOURCE.AUTO IGNITION TEMPERATURE OF SUBSTANCESEXCEEDS ITS FLASHPOINT.SUCH CONDITIONS CAN OCCUR DUE TO EXTERNAL HEATING -A FRYING PAN THAT OVERHEATS CAUSING THE OIL TOAUTOIGNITE, AN EXHAUST-PIPE FROM A CAR DRIVING OVERDRY GRASS OR STRAW CAN CAUSE IT TO AUTO-IGNITE- ORTHEY CAN OCCUR DUE TO CHEMICAL OR BIOLOGICALPROCESSES - A SILO FIRE CAN OCCUR BECAUSE OF THEBIOLOGICAL PROCESSES IN HUMID ORGANIC MATERIAL.
  • 28. VOLATILITYVOLATILITY IS HOW READILY A LIQUIDWILL EVAPORATE.THE VOLATILITY OF A SUBSTANCE ISCLOSELY LINKED TO ITS BOILING POINT.THE HIGHER THE BOILING POINT OF ALIQUID THE HARDER IT WILL BE FOR THELIQUID TO EVAPORATE.THE LOWER THE BOILING POINT, THEGREATER THE FIRE RISK.
  • 29. DEFLAGRATIONN & DETONATIONTHE FEROCITY OF AN EXPLOSIONDEPENDS ON THE SPEED OF THE FLAMEIF THE FLAME SPREAD REMAINS LOWERTHAN 340 M/S THE EXPLOSION IS CALLED ADEFLAGRATION.IF THIS SPEED EXCEEDS 340 M/S -AND THEYCAN REACH UP TO 1800 TO 2000 M/S- IT ISCALLED DETONATION.THE DIFFERENCE IS BEING FASTER OR SLOWERTHAN THE SPEED OF SOUND, SUPERSONIC ANDSUBSONIC.
  • 30. FLASHOVERIN A COMPARTMENT FIRE THERE CAN COME ASTAGE WHERE THE TOTAL THERMAL RADIATIONFROM THE FIRE PLUME, HOT GASES AND HOTCOMPARTMENT BOUNDARIES CAUSES THEGENERATION OF FLAMMABLE PRODUCTS OFPYROLYSIS FROM ALL EXPOSED COMBUSTIBLESURFACES WITHIN THE COMPARTMENT.GIVEN A SOURCE OF IGNITION, THIS WILL RESULT INTHE SUDDEN AND SUSTAINED TRANSITION OF AGROWING FIRE TO A FULLY DEVELOPED FIRE.......THIS IS CALLED FLASHOVER......MAIN FEATURE OF A FLASHOVER IS THAT THERE ISTRANSITION TO A STATE OF TOTAL FIRE
  • 31. A TIME COMES WHEN THE FLAMESCEASE TO BE LOCALISED ANDSPREADS TO THE WHOLECOMPARTMENT VOLUME.FIRE CHANGES FROM A SURFACEPHENOMENON TO A VOLUMEPROCESS
  • 32. BACKDRAFTLIMITED VENTILATION CAN LEAD TO A FIRE IN ACOMPARTMENT PRODUCING FIRE GASES,CONTAINING SIGNIFICANT PROPORTIONS OFPARTIAL COMBUSTION PRODUCTS AND UNBURNTPYRO LYSIS PRODUCTS (UNDER-VENTILATED FIRE).IF THESE ACCUMULATE, THEN THE ADMISSION OFAIR WHEN AN OPENING IS MADE TO THECOMPARTMENT CAN LEAD TO A SUDDEN INCREASEOF THE FIRE.THIS INCREASE IN FIRE, MOVING THROUGH THECOMPARTMENT AND OUT OF THE OPENING, ISCALLED BACKDRAFT
  • 33. FIRE SPREAD
  • 34. FIRE SPREAD• FIRE SPREADS QUICKLY &GEOMETRICALLY• RELEASED HEAT INCREASESTEMPERATURE IN THE VICINITY• HIGH TEMPERATURE CAUSESSELF IGNITION IN OTHER FUELS
  • 35. FIRE SPREADTHE HEAT LIBERATED BY THE FIRE ALSO CAUSESTHE SURROUNDING MATERIALS TO WARM UP. THEHEAT TRANSFER IS ACCOMPLISHED BY THREEMEANS, USUALLY SIMULTANEOUSLY:CONDUCTIONCONVECTIONRADIATION
  • 36. CONDUCTION• DIRECT THERMAL ENERGY TRANSFER DUE TO CONTACT.• MATERIALS CONDUCT HEAT AT VARYING RATES. METALS ARE VERY GOOD CONDUCTORS WHILE CONCRETE AND PLASTICS ARE VERY POOR CONDUCTORS, HENCE GOOD INSULATORS• NEVERTHELESS A FIRE IN ONE SIDEWALL OF A COMPARTMENT WILL RESULT IN THE TRANSFER OF HEAT TO THE OTHER SIDE OF THE WALL.
  • 37. CONVECTION• HEAT. TRANSFER THROUGH A LIQUID OR GAS• CAUSED BY DENSITY DIFFERENCE OF THE HOT MOLECULES COMPARED TO THE COLD ONES (eg. BOILING WATER)• HOT AIR, GASES EXPAND AND RISE.• CONVECTION NORMALLY DETERMINES THE GENERAL DIRECTION OF THE FIRESPREAD.• CONVECTION CAUSES FIRES TO RISE AS HEAT RISES
  • 38. RADIATION• ELECTROMAGNETIC WAVE TRANSFER OF HEAT TO AN OBJECT.• WAVES TRAVEL IN ALL DIRECTIONS FROM THE FIRE AND MAY BE REFLECTED OR ABSORBED BY A SURFACE.• ABSORBED HEAT RAISES THE TEMPERATURE OF THE MATERIAL BEYOND ITS IGNITION POINT, CAUSING IT TO IGNITE.
  • 39. FIRE SPREAD- CUBE MODEL HIGHEST DANGERLESS LESSDANGER DANGER LEAST DANGER
  • 40. STAGES OF COMBUSTION
  • 41. FACTORS AFFECTING FIRE DEVELOPMENT PROVIDING THAT THERE IS SUFFICIENT FUELAND OXYGEN AVAILABLE THE FIRE MAY TOTALLYINVOLVE THE COMPARTMENT. THE ITEMS FIRST IGNITED IS SUFFICIENTLYFLAMMABLE TO ALLOW FLAME SPREAD OVER ITSSURFACES. THE HEAT FLUX FROM THE FIRST FUELPACKAGE.IS SUFFICIENT TO IRRADIATE ADJACENT FUELPACKAGES WHICH IN TURN WILL BEGIN TO BURN. SUFFICIENT FUEL EXISTS. OPEN OR WELL-SEALED COMPARTMENT.
  • 42. FLASH OVERA TIME COMES WHEN THE FLAMESCEASE TO BE LOCALISED ANDSPREADS TO THE WHOLECOMPARTMENT VOLUME.FIRE CHANGES FROM A SURFACEPHEMENON TO A VOLUME PROCESS
  • 43. FLASHOVER FLASH OVER