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UNIT 9 FIRE

UNIT 9 FIRE. FIRE. When a substance enters into a chemical reaction with oxygen, oxidization occurs. Fire is a case of oxidization. Three things are required for a fire: combustible substance (fuel), heat oxygen. heat. oxygen. FIRE. combustible substance.

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UNIT 9 FIRE

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  1. UNIT 9FIRE FIRE

  2. When a substance enters into a chemical reaction with oxygen, oxidization occurs. • Fire is a case of oxidization.

  3. Three things are required for a fire: • combustible substance (fuel), • heat • oxygen.

  4. heat oxygen FIRE combustible substance • This is called fire triangle.

  5. Fire extinguishing is achieved by removing one of these items.

  6. CLASSIFICATION OF FIRE • Fires are classified as class A, B, C, and D according to the nature of the combustibles involved

  7. Class A fires occur in ordinary combustible materials such as wood, cloth, paper, and similar materials. • Class A fires are usually extinguished with water, using high or low velocity fog or solid streams.

  8. Class B fires are those that occur in the vapour-air mixture over the surface of flammable liquids, such as gasoline, diesel oil, paints, thinners, solvents, and lubricating oils. • Dry chemical, aqueous film forming foam (AFFF), HaIon 1301, carbon dioxide (CO2), or water fog can be used to extinguish class B fires.

  9. Class C fires are those which occur in electrical equipment. • Non-conducting extinguishing agents, such as CO2 and Halon 1301 are used to extinguish class C fires. • Carbon dioxide and Halon 1301 are preferred because they leave no residue.

  10. Class D fires occur in combustible metals, such as magnesium, titanium, and sodium. • Most class D fires are fought by applying large amounts of water on the burning material to cool it down below its ignition temperature. • Magnesium fires can be smothered by covering the magnesium with lots of dry sand.

  11. FIRE EXTINGUISHING Basic fire extinguishing methods are: • Smothering • Cooling • Breaking the chain reaction • Removing the combustible material

  12. Smothering is preventing oxygen supply by • mixing, • separation, • emulsification • dilution.

  13. Mixing is done by providing a non-combustible or inert gas to reduce the level of oxygen to support a fire.

  14. Separation is done by preventing the contact between the burning substance and oxygen by means of an agent

  15. Emulsification is whipping water droplets into the burning surface of liquid to create an emulsion

  16. Dilution is mixing the combustible liquid with water to decrease the combustibility.

  17. Cooling is to eliminate the heat side of the fire triangle. • The fire is cooled by applying something that will absorb the heat.

  18. Some substances have the effect of preventing and reducing the chemical reaction which causes a fire. • These substances are called inhibitors.

  19. Dry chemical fire extinguishing agents and Halon 1301 do not extinguish fires by cooling or smothering. • Instead, they interrupt the chemical reaction of the fuel and oxygen.

  20. Removing the combustible material may be done if it is possible to cut off leakage or source of combustible substance.

  21. FIRE EXTINGUISHING AGENTS • An extinguishing agent is a substance that will put out a fire. Fire extinguishing agents are three types according to their effect: • Smothering agents –carbon dioxide, foam, light water , steam • Cooling agents - water • Agents to break the chain reaction.- dry chemical, halon (halogenated hydrocarbon

  22. Cooling is the most common method of fire extinguishment, and water is the most effective cooling agent.

  23. Foam is a highly effective extinguishing agent for smothering large fires. AFFF is synthetic, film-forming foam designed for use in shipboard fire fighting systems.

  24. Dry chemicals are; sodium bicarbonate, ammonium phosphate, potassium bicarbonate.

  25. Gases are carbon dioxide (CO2) and halogenated hydrocarbons. It extinguishes a fire by displacing oxygen, making it unavailable for the combustion process. Halon 1301 is stored in compressed gas cylinders for shipboard use.

  26. 1- What happens when a substance enters into a chemical reaction with oxygen?

  27. 2- What forms a fire triangle?

  28. 3-What is generally used to extinguish class A fires?

  29. 4- What are the main fire extinction methods?

  30. 5- What are the techniques of smothering?

  31. 6- Is foam the most common cooling agent?

  32. 7-What are the gas fire extinguishing agents?

  33. SOME WORDS Aqueous (adj)-Relating to water, watery.

  34. Combustible (adj.)-That burns easily, flammable. Combustion (n)-The process of burning.

  35. Dilution (n) -Reducing the concentration by adding water.

  36. Emulsion (n)-Suspension a liquid within another.

  37. Extinguish (v) -To put out a fire.

  38. Smother (v) -To deprive of oxygen or prevent from breathing.

  39. Find the adjective forms of following words in the text. combustion …………………… danger …………………… explosion …………………… flame ……………………

  40. Underline the correct word or phrase in bold. 1- Fires that occur in wood, paper or cloth are class A / class B fires.

  41. 2- AFFF is a gas / foam fire extinguishing agent.

  42. 3- Smothering / Oxidization is a fire extinguishing method.

  43. 4- Mixing the combustible liquid with water to reduce the combustibility is dilution / emulsification.

  44. 5- Cooling eliminates the oxygen / heat side of fire triangle.

  45. 6- Water is a cooling / smothering agent.

  46. 7- Water is not used for fires that occur in electrical equipment because it is a conducting / non-conducting agent.

  47. 8- Halon 1301 / Foam is an inhibitor.

  48. 1-What is the major extinguishing agent for class A fires? a. sand b. dry chemical c. Halon d. water e. CO2

  49. 1-What is the major extinguishing agent for class A fires? d. water

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