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Chapter 9

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  • 1. 9DefensiveOperations
  • 2. 9 Learning Objectives (1 of 9)• Compare and contrast a defensive versus offensive fire attack, explaining the key differences.• Explain why an offensive attack is preferred over a defensive attack.• Enumerate conditions that would lead to a defensive attack.
  • 3. 9 Learning Objectives (2 of 9)• Describe how collapse zone dimensions are determined.• Evaluate the effectiveness of master streams operated from distances required to maintain a safe collapse zone.• Discuss the positive and negative effects of operating a hose stream into a window or roof opening.
  • 4. 9 Learning Objectives (3 of 9)• Describe conditions when a direct defensive attack is preferred as compared to an indirect defensive attack (i.e., covering exposures).• Describe how water should be applied when protecting an exposure from radiant heat.
  • 5. 9 Learning Objectives (4 of 9)• Compare and contrast the use of handheld hose streams versus master stream appliances during defensive operations.• List two ways the water utility may be able to increase the total water supply at the incident scene.
  • 6. 9 Learning Objectives (5 of 9)• Compare and contrast the use of fog versus solid streams during a defensive attack.• Estimate staffing and apparatus needs when operating master streams.• Define conflagrations and group fires.
  • 7. 9 Learning Objectives (6 of 9)• List common problems leading to conflagrations.• Explain tactics used to control a conflagration.• Discuss why conflagrations are likely to occur immediately after a natural disaster.
  • 8. 9 Learning Objectives (7 of 9)• List reasons for a non-attack strategy.• Given a scenario, calculate the dimensions of the collapse zone.• Prioritize exposures based on fire conditions, occupancy, and weather factors.
  • 9. 9 Learning Objectives (8 of 9)• Develop an incident action plan for a defensive fire.• Develop an incident action plan for a conflagration.• Apply defensive tactics to a defensive fire attack.
  • 10. 9 Learning Objectives (9 of 9)• Apply defensive tactics to a conflagration.• Evaluate staffing, water supply, and apparatus needs for a large-scale defensive fire.• Apply NIMS to a defensive fire scenario.• Determine the probability of a conflagration for a specified response area.
  • 11. 9 Overview (1 of 2)• Offensive fire attack – Preferred strategy• Defensive fire attack – Limits operations to the exterior – Results in larger property loss – Limits rescue options
  • 12. 9 Overview (2 of 2)• Offensive/defensive decision based on: – Risk-versus-benefit analysis • Solid fire-ground information • Training and experience• Staffing available to accomplish interior attack, water supply, ventilation
  • 13. 9 Defensive Attack (1 of 2)• Objective: save property and/or protect the environment• Easier to handle• Pose fewer risks if the proper precautions are taken
  • 14. 9 Defensive Attack (2 of 2)• Situations: – Structural integrity concerns, fire conditions, or other hazards prohibit entry – Resource needs outweigh resource capabilities. – Risk-versus-benefit analysis indicates that the risk is too great.
  • 15. 9 Collapse Zone (1 of 2)• Equal to the height of the building plus an allowance for debris to scatter – Anything less = calculated risk• Distance equal to 1½ times the height of the building• Can be pre-planned – Estimated floor height = 12′ per floor
  • 16. 9 Collapse Zone (2 of 2)• Non-attack strategy: tall buildings – Water application distance for master streams• Width of street = limiting factor – Building evaluated to determine safest position• IC must consider expected benefits. – Risk-versus-benefit analysis
  • 17. 9 Evaluating Exposures• Two types: internal and external• Internal – Fire extends from one area to another within a structure.• External – Surrounding buildings/property
  • 18. 9 Defensive Streams• May spread the fire inside the building• Fog streams may push fire. – May also fill an area with steam, helping the suppression effort• Exterior streams may push fire into concealed spaces.• Elevated streams may push vented fires back into the building.
  • 19. 9 External Exposures• Protecting external exposures is critical.• Should be evaluated in terms of: – Life safety – Extinguishment – Property conservation
  • 20. 9 Prioritizing Exposures• Based on: – Distance between exposed structures – Volume and location of fire• Radiant heat increases as flame front increases. – Extinguish main volume of fire
  • 21. 9 Radiant Heat• Inversely proportional to the square of the distance between the heat source and the exposure – Closer the buildings = greater radiant heat – Exposures higher than the fire are also at greater risk.
  • 22. 9 Protecting Exposures• Options depend on: – Available staffing – Apparatus resources• Wetting the exposure is most effective way.• Directing a stream between buildings is less effective. – Radiant heat travels through transparent materials such as water.
  • 23. 9 Master Streams (1 of 2)• Defensive operations – Can apply more water from a greater distance with fewer personnel
  • 24. 9Master Streams (2 of 2)
  • 25. 9 Elevated Master Streams• May hinder upward and outward movement of heat and smoke – Usually detrimental to the operation• May push fire back into the building – Spreads fire into uninvolved areas. – Reverses positive effects of ventilation
  • 26. 9 Water Supply Needs• Defensive operations may be more challenging than offensive attacks.• Master streams can require total pump capacity of apparatus. – Even reliable water systems can be exhausted. – Large-diameter hose is effective. – Water relay remains a possibility.
  • 27. 9 Exterior Stream Position• Considerations: – Safety – Ability to apply water to exposures and interior of the building • Preferably will not push fire into uninvolved areas
  • 28. 9 Nozzle Type• IC should know the advantages/disadvantages of nozzles.• Solid-stream nozzle – Greatest reach and penetrating ability – Best suited for attack on main body of the fire• Variable-stream nozzle – Fog pattern – Straight stream
  • 29. 9 Staffing/Apparatus Needs• Offensive attack: personnel intense – More fire fighters for hand lines• Defensive attack: apparatus intense – Master streams handled by one person – Pumpers for water supply or drafting – Tankers for water shuttle operation
  • 30. 9 Conflagrations (1 of 3)• A fire with major building-to-building flame spread over some distance• Departments should recognize the challenge. – Determine the probability in their area.• Special tactics needed
  • 31. 9 Conflagrations (2 of 3)• Historical – Rome, London, Constantinople – Jamestown, Virginia – Plymouth, Massachusetts – Boston
  • 32. 9 Conflagrations (3 of 3)• Recent – Oakland/Berkeley, California – San Jose, California
  • 33. 9 Wildland/Urban Interface• Fires spreading from wildlands into an urban area, destroying large numbers of buildings – Peshtigo, Wisconsin • October 7, 1871 • Same day as The Great Chicago Fire • Killed 1200 people (some estimate as many as 2000 fatalities) and destroyed 17 towns.
  • 34. 9 Contributing Factors (1 of 2)• Closely built structures• Wood shingle roofs (most often cited cause)• Poor water supplies• Dilapidated structures
  • 35. 9 Contributing Factors (2 of 2)• Large-scale, combustible construction projects• Developments near wildlands• Built-up areas near high-hazard locations
  • 36. 9 Group Fires• Similar to conflagrations – Fire is confined within a complex or among adjacent buildings. – Potential to become conflagrations – Smaller in scale
  • 37. 9 Strategies and Tactics• Important to understand how fires spread – High convected heat – Flying brands – High radiant heat • Primary means of fire extension
  • 38. 9 Priorities• Life safety• Extinguishment• Evacuating people before they are threatened is key to success – Proactive measure
  • 39. 9 Evacuation• Area must be beyond the secondary line of defense – Wide-perimeter should be maintained• Evacuation should be handled by police department. – A police branch in the IMS is a good organizational tactic at large-scale fires.
  • 40. 9 Water Supply• Will be challenged by large-fire tactics• Priorities: – Water conservation – Maintaining fire break – Protecting exposures
  • 41. 9 Tactical Elements (1 of 2)• Evacuate and rescue people in imminent danger• Evacuate people in the endangered area beyond the secondary line of defense• Set up a line of defense with natural or artificial fire breaks
  • 42. 9 Tactical Elements (2 of 2)• Establish a secondary line of defense• Narrow the flame front• Maintain brand patrol
  • 43. 9 Non-Attack• Seldom used strategy• ICs fail to recognize a total loss.• Used when: – Environmental concerns are paramount. – Safe offensive attack is not possible. – Defensive attack is not practical.
  • 44. 9 Summary (1 of 4)• Three possible operations at a structure fire: – Offensive – Defensive – Non-attack• A proper size-up will indicate which operation is appropriate.
  • 45. 9 Summary (2 of 4)• Offensive attack – Best chance of saving lives and property – Operation of choice when justified by proper size-up
  • 46. 9 Summary (3 of 4)• Defensive attack – Rarely an effective means of saving lives in the building of origin. – May be the IC’s only reasonable option – Indicated by proper size-up – Strategic objectives: • To protect internal and external exposures while extinguishing the fire
  • 47. 9 Summary (4 of 4)• Non-attack posture – May be best option when: • Offensive attack is not possible • Building and surroundings are a total loss