Chapter 08


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Chapter 08

  1. 1. Wildland Fires Chapter 8
  2. 2. Objectives <ul><li>Explain the basic fire combustion principles and be able to apply them to wildland fires, and differentiate wildland fire behavior from structural fire behavior </li></ul><ul><li>Examine how weather conditions impact wildland fuels and the behavior of wildland fires </li></ul>
  3. 3. Objectives (cont’d.) <ul><li>Describe the various parts of a wildland fire and identify how fire behavior impacts the methods of fire fighting wildland fires </li></ul><ul><ul><li>Include some of the special techniques needed to extinguish and control these fires </li></ul></ul><ul><li>Describe the method used to classify resources used on wildland fires and how fire behavior impacts the type and amount of resources needed to suppress wildland fires </li></ul>
  4. 4. Objectives (cont’d.) <ul><li>Describe the various resources and tools used in extinguishment of wildland fires </li></ul>
  5. 5. Introduction <ul><li>Vast difference between wildland fire fighting and structural fire fighting </li></ul><ul><li>This chapter centers on differences and similarities between both types of fire fighting and differing extinguishment methods </li></ul><ul><li>Triangle model still used by most wildland agencies </li></ul>
  6. 6. The Fire Triangle for Wildland Fires <ul><li>In wildland fire fighting, the heat is cooled, the fuel is removed, or the oxygen is excluded from the fuel </li></ul><ul><ul><li>Water directed by hose lines, hand tools, or machines </li></ul></ul><ul><ul><li>Dirt or foam to smother, cool, and exclude oxygen </li></ul></ul>
  7. 7. The Fire Triangle for Wildland Fires (cont’d.) Figure 8-1 The fire triangle shows the wildland fire combustion process
  8. 8. Heat Removal <ul><li>Represents removal or reduction of the ignition temperature of the fuel </li></ul><ul><li>Water is most effective, but other materials used </li></ul><ul><li>Yellowstone has used CAFS </li></ul><ul><li>Foam and fire retardants can be applied by aircraft and special foam application-equipped vehicles such as the CAFS </li></ul>
  9. 9. Heat Removal (cont’d.) Table 8-1 Foam expansion rate and drain time
  10. 10. Fuel Removal <ul><li>Most common method of extinguishment </li></ul><ul><li>Accomplished by: </li></ul><ul><ul><li>Cutting or scraping </li></ul></ul><ul><ul><li>Using bulldozers and/or hand crews </li></ul></ul><ul><ul><li>Backfiring operations </li></ul></ul><ul><ul><ul><li>Fuel is burned in front of the main fire </li></ul></ul></ul>
  11. 11. Oxygen Removal <ul><li>Accomplished by: </li></ul><ul><ul><li>Throwing dirt at base of the flames or area of combustion to cool down/exclude oxygen </li></ul></ul><ul><li>Aircrafts drop either water or flame retardant solutions </li></ul><ul><ul><li>Must degenerate or be biodegradable generally within thirty days </li></ul></ul>
  12. 12. Wildland Heat Movement <ul><li>Heat moves in four ways: </li></ul><ul><ul><li>Conduction: transfer of heat within material itself </li></ul></ul><ul><ul><li>Convection: transfer of heat by liquid or gas </li></ul></ul><ul><ul><li>Radiation: radiates energy ahead of fire </li></ul></ul><ul><ul><li>Direct flame impingement: flame front is moving upslope where the flames lay down or move at an angle to the slope </li></ul></ul>
  13. 13. Wildland Heat Movement (cont’d.) Figure 8-4 A wildland fire can move uphill quickly when the flames lean to an angle and heat the fuel by convection currents and direct flame
  14. 14. Wildland Fire Size-Up <ul><li>Five-step decision-making process: </li></ul><ul><ul><li>Factors impacting life safety </li></ul></ul><ul><ul><li>Factors impacting property safety </li></ul></ul><ul><ul><li>Factors that may harm the environment </li></ul></ul><ul><ul><li>Factors that will harm wild life </li></ul></ul><ul><ul><li>The availability of needed fire fighting resources </li></ul></ul>
  15. 15. Behavior of Wildland Fires <ul><li>Fire behavior triangle </li></ul><ul><ul><li>Affected by weather, topography, and fuels </li></ul></ul><ul><li>Burning index: </li></ul><ul><ul><li>A number in an arithmetic scale determined from fuel moisture content, wind speed, and other selected factors that affect burning conditions </li></ul></ul><ul><ul><li>Index from which the ease of fire ignition and their probable behavior may be estimated </li></ul></ul>
  16. 16. Weather <ul><li>Temperature: fuel temperature is necessary to initiate and continue fire combustion process </li></ul><ul><li>Stable and unstable air masses: vertical temperature distribution within air mass and vertically moving parcel of air </li></ul><ul><li>Temperature inversion: cooler air close to ground surface and warmer air above cooler air </li></ul><ul><li>Relative humidity: ratio or amount of water vapor in air to maximum amount air can hold </li></ul>
  17. 17. Weather (cont’d.) <ul><li>Wind velocity and direction: movement of warm to cooler air setting a circulation pattern of rising and descending air currents </li></ul><ul><li>Foehn winds: when air is pushed over high elevations and flows downhill </li></ul><ul><li>Fuel moisture: cooling effect from moisture in air </li></ul><ul><li>Dust devils and fire whirls: indicators of unstable surface conditions and will cause erratic fire behavior </li></ul>
  18. 18. Topography <ul><li>Slope: fuel preheated by direct flame impingement and convective air currents; draft effect is created </li></ul><ul><li>Aspect: direction a slope faces to the sun </li></ul><ul><li>Elevation: influences how air moves from the valleys that are warming to the cooler ridges, positioning of warm/cool air masses in thermal belts, and length and type of fuel </li></ul>
  19. 19. Topography (cont’d.) <ul><li>Canyons: wideness or narrowness determines effect </li></ul><ul><li>Saddles: low topography between two high points </li></ul><ul><li>Ridges: elements that divide the terrain </li></ul><ul><li>Chimneys: steep, narrow draws in canyons </li></ul>
  20. 20. Figure 8-5 Elevation changes fuel types
  21. 21. Fuels <ul><li>Fuel loading: the amount of fuel available to burn in a given area </li></ul><ul><li>Light fuels: Grass and other small plants occur on the floor of all forests </li></ul><ul><li>Medium fuels: Medium fuels consist of brush that is six feet in height or lower </li></ul><ul><li>Heavy fuels: brush taller than six feet; timber, slash, and standing conifer and hardwood trees </li></ul>
  22. 22. Fuels (cont’d.) <ul><li>Fuel shape and arrangement: may determine how the fuel can affect the ignition and spread of a fire </li></ul><ul><li>Aerial fuels: include all green and dead materials located in the upper forest canopy </li></ul><ul><ul><li>Crown fires: advance along tree tops and shrubs independently of the surface fire </li></ul></ul>
  23. 23. Fuels (cont’d.) <ul><li>Amount of moisture in the fuel will affect how easily it will ignite and how intensely it will burn </li></ul><ul><ul><li>Dead fuel moisture </li></ul></ul><ul><ul><li>Living fuel moisture </li></ul></ul><ul><li>Time lag: time it takes for the moisture content of fuel and the surrounding air to equalize </li></ul><ul><li>The warmer the fuel, the less heat is required to ignite it </li></ul>
  24. 24. Fire Behavior- Identifying Parts of a Wildland Fire Figure 8-7 Parts of a wildland fire
  25. 25. Spotting <ul><li>Occurs when wind and convection columns broadcast hot fire brands into the unburned fuel (green area) ahead of the main fire </li></ul><ul><li>Convection columns: thermally produced column of gases, smoke, and debris produced by a fire </li></ul>
  26. 26. Large Fires <ul><li>Can become so large that the combustion process creates its own indraft of oxygen </li></ul><ul><ul><li>Backfire or burn out the fuel near the fire edge in an effort to separate the fire from the fuel </li></ul></ul><ul><ul><li>Works well when the backfire is ignited to be entrained into the main fire </li></ul></ul>
  27. 27. Area Ignition <ul><li>Occurs when: </li></ul><ul><ul><li>Spot fires take place in an area with unburned vegetation </li></ul></ul><ul><ul><li>Spot fires are burning in a bowl or canyon or an area where the heat from the spot fires is trapped </li></ul></ul><ul><li>Pre-heated vegetation in the area can explode into combustion </li></ul>
  28. 28. Fire Resources <ul><li>Include engine companies, water tenders or trucks that carry water, hand crews, aircraft (both fixed wing and rotary wing), and bulldozers </li></ul><ul><li>Field operations guide: a small notebook designed to be carried in the shirt pocket, containing complete data on the ICS, including job titles, descriptions, and equipment classification systems </li></ul>
  29. 29. Engine Types <ul><li>Both air and ground are used and very versatile </li></ul><ul><li>Can fight fire both day and night </li></ul><ul><li>Not restricted by visibility </li></ul><ul><li>Can deliver water at various capacities </li></ul><ul><li>Can transport a crew to fire with their equipment </li></ul><ul><li>Crew can construct hand line </li></ul>
  30. 30. Hand Crew Types <ul><li>Biggest portion of suppression personnel </li></ul><ul><li>Use hand and power tools to reduce the fuel side of the triangle </li></ul><ul><li>Type I: These persons are highly trained to work on all fires directly on the fire line </li></ul><ul><li>Type II: These persons have some training with fire line work restrictions </li></ul>
  31. 31. Bulldozer Types <ul><li>Provide a tactically balanced and integrated fire suppression force </li></ul><ul><li>Attack the fuel side of the triangle </li></ul><ul><li>Type I: Heavy D-7, D-8, D-9 </li></ul><ul><ul><li>Heavy, thick brush, timber or road construction </li></ul></ul><ul><li>Type II: Medium D-6 and HD-11 </li></ul><ul><ul><li>Heavy to medium brush </li></ul></ul><ul><li>Type III: Light D-4 and HD-6 </li></ul><ul><ul><li>Light fuels, grass, fast-moving fire </li></ul></ul>
  32. 32. Fixed-Wing Aircraft Types <ul><li>Attack the heat leg of the fire triangle </li></ul><ul><li>Cool with water or retardants </li></ul><ul><li>Type I: capacity of 3,000 gallons </li></ul><ul><li>Type II: capacity of 1,800 to 2,999 gallons </li></ul><ul><li>Type III: capacity of 600 to 1,799 gallons </li></ul><ul><li>Type IV: capacity of 100 to 599 gallons </li></ul>
  33. 33. Rotary-Wing Helicopters <ul><li>Principle advantage of a helicopter is its ability to operate from locations close to and on fire line </li></ul><ul><li>Cannot carry as much as the fixed-wing aircraft, </li></ul><ul><li>Work closer to houses and pinpoint application of the retardant more precisely </li></ul><ul><li>Use for application water or retardant chemicals, </li></ul><ul><li>Carry injured firefighters </li></ul>
  34. 34. Rotary-Wing Helicopters (cont’d.) Figure 8-10 Rotary-wing aircraft
  35. 35. Wildland Fire Tactics - Direct Method of Attack <ul><li>Attack itself is directed to edge of burning fire </li></ul><ul><li>Firing out: to “burn out” fuel between the main fire line and the line being constructed for fire control </li></ul><ul><li>May not be effective against intensely hot or fast-moving fire </li></ul><ul><li>Requires close coordination of all crews </li></ul>
  36. 36. Wildland Fire Tactics - Indirect Method of Attack <ul><li>Construct control lines or backfire the fuel ahead of hot, intense fires, and large fires </li></ul><ul><ul><li>Constructed control lines located using favorable topography </li></ul></ul><ul><li>Work away from large amounts of heat and smoke and thus reduce fatigue </li></ul><ul><li>Fire is not being extinguished when control lines are being put into place </li></ul><ul><li>Unburned fuel may be left inside control line </li></ul>
  37. 37. Wildland Fire Tactics - Combination Attack <ul><li>Advantages of direct attack and indirect methods </li></ul><ul><li>Work directly on fire line in areas that are safe and can be reached quickly in an effort to contain as much of the fire as possible </li></ul><ul><li>Crews begin to work indirectly in areas where the fire line cannot be attacked directly to put in and burn out a clean line </li></ul>
  38. 38. Application of Attack Methods <ul><li>Tandem action: direct attack method with the attacking forces working in tandem (one unit following the other) </li></ul><ul><li>Pincer action: moving crews along both flanks of the fire to a point where the flanking forces move closer together in a pinching action near the head of the fire </li></ul>
  39. 39. Application of Attack Methods (cont’d.) <ul><li>Envelopment action: taking suppression action on a fire at many points and in many directions simultaneously </li></ul><ul><li>Parallel method: method of suppression in which the fire line is constructed approximately parallel to and just far enough from the fire edge to enable personnel and equipment to work effectively </li></ul>
  40. 40. Summary <ul><li>Original fire triangle model is often applied rather than the newer fire tetrahedron model </li></ul><ul><li>Weather, fuel, topography and the combination thereof affect the fire behavior </li></ul><ul><li>Three methods of attack: </li></ul><ul><ul><li>Direct </li></ul></ul><ul><ul><li>Indirect </li></ul></ul><ul><ul><li>Combination attack </li></ul></ul>