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Essentials of Fire Fighting , 5 th Edition

Essentials of Fire Fighting , 5 th Edition. Chapter 3 — Fire Behavior Firefighter I. Chapter 3 Lesson Goal. After completing this lesson, the student shall be able to summarize physical and chemical changes and reactions that occur with fire and the factors involved in fire development. .

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Essentials of Fire Fighting , 5 th Edition

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  1. Essentials of Fire Fighting, 5th Edition Chapter 3 — Fire Behavior Firefighter I

  2. Firefighter I Chapter 3 Lesson Goal After completing this lesson, the student shall be able to summarize physical and chemical changes and reactions that occur with fire and the factors involved in fire development.

  3. Firefighter I Specific Objectives 1. Describe physical and chemical changes of matter related to fire. 2. Discuss modes of combustion, the fire triangle, and the fire tetrahedron. 3. Explain the difference between heat and temperature. (Continued)

  4. Firefighter I Specific Objectives 4. Describe sources of heat energy. 5. Discuss the transmission of heat. 6. Explain how the physical states of fuel affect the combustion process. 7. Explain how oxygen concentration affects the combustion process. (Continued)

  5. Firefighter I Specific Objectives 8. Discuss the self-sustained chemical reaction involved in the combustion process. 9. Describe common products of combustion. 10. Distinguish among common classifications of fires. (Continued)

  6. Firefighter I Specific Objectives 11. Describe the stages of fire development within a compartment. 12. Summarize factors that affect fire development within a compartment. 13. Describe methods used to control and extinguish fire.

  7. Firefighter I Matter is… anything that occupies space and has mass (weight).

  8. Firefighter I Physical and Chemical Changes of Matter Related to Fire Physical change Water freezing Water boiling Chemical reaction Reaction of two or more substances to form other compounds Oxidation (Continued)

  9. Firefighter I Physical and Chemical Changes of Matter Related to Fire Chemical and physical changes Usually involve exchange of energy Potential energy released and changed to kinetic energy Exothermic reaction Endothermic reaction

  10. Combustion — Modes Firefighter I

  11. Firefighter I Fire Triangle

  12. Firefighter I Fire Tetrahedron

  13. Firefighter I Heat as Energy Heat is a form of energy. Potential energy — Energy possessed by an object that may be released in the future Kinetic energy — Energy possessed by a moving object

  14. Firefighter I Temperature Temperature is a measurement of kinetic energy Heat energy moves from objects of higher temperature to those of lower temperature. Understanding this movement is important

  15. Firefighter I Measuring energy Not possible to measure directly Work means increasing temperature Measured in joules in International System of Units or metric system Measured in British thermal units in customary system

  16. Firefighter I Scales Used to Measure Temperature Celsius — Metric Fahrenheit — Customary

  17. Firefighter I Conversion of Energy Into Heat Heat is the energy component of tetrahedron Fuel is heated = temperature increases Starting ignition Forms of ignition

  18. Firefighter I Chemical Heat Energy Most common heat source in combustion reactions Oxidation almost always results in production of heat Self-heating

  19. Firefighter I Electrical Heat Energy Can generate temperatures high enough to ignite any combustible materials near heated area Can occur as Resistance Overcurrent/overload Arcing Sparking

  20. Firefighter I Mechanical Heat Energy Generated by friction or compression Movement of two surfaces against each other creates heat of friction Movement results in heat and/or sparks being generated Heat of compression generated when gas compressed

  21. Firefighter I Transfer of Heat Basic to study of fire behavior Affects growth of any fire Knowledge helps firefighters estimate size of fire before attacking Heat moves from warmer objects to cooler objects (Continued)

  22. Firefighter I Transfer of Heat Rate related to temperature differential of bodies and thermal conductivity of material Greater the temperature differences between bodies, greater the transfer rate Measured as energy flow over time

  23. Firefighter I Conduction Transfer of heat within a body or to another body by direct contact Occurs when a material is heated as a result of direct contact with heat source Heat flow depends on several factors

  24. Firefighter I Convection Transfer of heat energy from fluid to solid surface Transfer of heat through movement of hot smoke and fire gases Flow is from hot fire gases to cooler components

  25. Firefighter I Radiation Transmission of energy as electromagnetic wave without intervening medium (Continued)

  26. Firefighter I Radiation Thermal radiation results from temperature Affected by several factors Energy travels in straight line at speed of light

  27. Firefighter I Passive Agents Materials that absorb heat but do not participate in combustion Fuel moisture = passive agent Relative humidity and fuel moisture

  28. Firefighter I Fuel Material being oxidized in combustion process Reducing agent Inorganic or organic; organic most common (Continued)

  29. Firefighter I Fuel Organic can be broken into: Hydrocarbon-based Cellulose-based Key factors influencing combustion process Physical state of fuel Distribution or orientation of fuel

  30. Firefighter I Gaseous Fuel Must be gaseous for flaming combustion Methane, hydrogen, etc. most dangerous because exists naturally in state required for ignition Has mass but no definite shape or volume

  31. Firefighter I Liquid Fuel Has mass and volume but no definite shape except for flat surface Assumes shape of container Will flow downhill and pool in low areas Density is compared to that of water Must be vaporized in order to burn

  32. Firefighter I Liquid Fuel Characteristics Flash point (Continued)

  33. Firefighter I Liquid Fuel Characteristics Fire point Surface area Solubility Fire fighting considerations

  34. Firefighter I Solid Fuel Definite size and shape May react differently when exposed to heat Pyrolysis evolves solid fuel into fuel gases/vapors. As it is heated, begins to decompose, giving off combustible vapors (Continued)

  35. Firefighter I Solid Fuel Commonly the primary fuel Surface-to-mass ratio — Primary consideration in ease or difficulty of lighting Proximity/orientation of solid fuel relative to source of heat affects the way it burns

  36. Firefighter I Heat of Combustion/Heat Release Rate Heat of combustion — Total amount of energy released when a specific amount of fuel is oxidized Usually expressed in kilojoules/gram (kJ/g) Heat release rate (HRR) — Energy released per unit of time as fuel burns Usually expressed in kilowatts (kW)

  37. Firefighter I Oxygen In air, is the primary oxidizing agent in most fires Air consists of about 21 percent oxygen Other materials can react with fuels in same way

  38. Firefighter I Oxygen Concentrations At normal ambient temperatures, materials can ignite/burn at concentrations as low as 14 percent. When limited, flaming combustion may diminish; combustion will continue in surface or smoldering mode. (Continued)

  39. Firefighter I Oxygen Concentrations At high ambient temperatures, flaming combustion may continue at much lower oxygen concentrations. Surface combustion can continue at extremely low oxygen concentrations. (Continued)

  40. Firefighter I Oxygen Concentrations When higher than normal, materials have different burning characteristics. Fires in oxygen-enriched atmospheres are difficult to extinguish and present a potential safety hazard. Flammable explosive range — Range of concentrations of fuel vapor and air

  41. Firefighter I Self-Sustained Chemical Reaction Very complex Example: Combustion of methane and oxygen (Continued)

  42. Firefighter I Self-Sustained Chemical Reaction

  43. Firefighter I Flaming Combustion • Sufficient heat causes fuel/oxygen to form free radicals, initiates self-sustained chemical reaction • Fire burns until fuel/oxygen exhausted or extinguishing agent applied • Agents may deprive process of fuel, oxygen, sufficient heat for reaction

  44. Firefighter I Surface Combustion Distinctly different from flaming combustion Cannot be extinguished by chemical flame inhibition Must be extinguished by working on one side of the fire triangle

  45. Firefighter I General Products of Combustion Include Heat, Smoke, Light Heat, smoke impact firefighters most Heat generated during fire helps spread fire Lack of protection from heat may cause burns and other health issues Toxic smoke causes most fire deaths

  46. Firefighter I Common Products of Combustion Carbon monoxide Hydrogen cyanide Carbon dioxide

  47. Firefighter I Hazards to Firefighters Toxic effects of smoke inhalation not results of any one gas Smoke contains a wide range of irritating substances that can be deadly Firefighters must use SBCA when operating in smoke

  48. Firefighter I Flame Visible, luminous body of a burning gas Becomes hotter, less luminous when burning gas mixes with proper amounts of oxygen Loss of luminosity caused by more complete combustion of carbon Product of combustion

  49. Firefighter I Class A Fires Involve ordinary combustible materials Primary mechanism of extinguishment is cooling to reduce temperature of fuel to slow or stop release of pyrolysis products

  50. Firefighter I Class B Fires Involve flammable and combustible liquids and gases Those involving gases can be extinguished by cutting off gas supply Can be extinguished with appropriately applied foam and/or dry chemical agents

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