Essentials of Fire Fighting[消防要點](-120)

1、Essentials of Fire Fighting, 5th EditionChapter 11 VentilationFirefighter IChapter 11 Lesson GoalAfter completing this lesson, the student shall be able to identify reasons and needs for various types of ventilation within a structure, distinguish which types of ventilation are most effective to var

2、ying situations, and perform duties related to ventilating a structure following the policies and procedures set forth by the authority having jurisdiction (AHJ).1Specific Objectives1.Describe reasons for fireground ventilation. 2.List considerations that affect the decision to ventilate. 3.Discuss

3、factors that are taken into account when deciding the need for ventilation. (Continued)2Specific Objectives4.Discuss vertical ventilation. 5.List safety precautions to observe when undertaking vertical ventilation. 6.List warning signs of an unsafe roof condition. (Continued)3Specific Objectives7.Di

4、scuss roof coverings and using existing roof openings for vertical ventilation purposes. 8.Discuss ventilation considerations for various types of roofs. 9.Describe trench or strip ventilation. (Continued)4Specific Objectives10.Explain procedures for ventilation of a conventional basement. 11.List f

5、actors that can reduce the effectiveness of vertical ventilation.12.Discuss horizontal ventilation. (Continued)5Specific Objectives13.Discuss considerations for horizontal ventilation. 14.Distinguish between advantages and disadvantages of forced ventilation. 15.Discuss negative-pressure ventilation

6、. (Continued)6Specific Objectives16.Discuss positive-pressure ventilation.17.Compare and contrast positive-pressure and negative-pressure ventilation. 18.Describe hydraulic ventilation. (Continued)7Specific Objectives19.List disadvantages to the use of hydraulic ventilation. 20.Explain the effects o

7、f building systems on fires or ventilation. 21.Ventilate a flat roof. (Skill Sheet 11-I-1)(Continued)8Specific Objectives22.Ventilate a pitched roof. (Skill Sheet 11-I-2)23.Ventilate a structure using mechanical positive-pressure ventilation. (Skill Sheet 11-I-3)24.Ventilate a structure using horizo

8、ntal hydraulic ventilation. (Skill Sheet 11-I-4)9Life Safety Reasons for Fireground VentilationIncreases firefighter safety by reducing interior temperature, increasing visibilityReduces chance of firefighters receiving steam burns when water applied(Continued)10Life Safety Reasons for Fireground Ve

9、ntilationReduces likelihood of sudden, hazardous changes in fire behaviorSimplifies, expedites search and rescue operations by removing smoke, gases that endanger trapped/unconscious occupants11Fire Attack and Extinguishment Reasons for Fireground VentilationPermits firefighters to more rapidly loca

10、te fire, proceed with extinguishmentWhen ventilation opening made in upper portion of building, chimney effect occurs(Continued)12Fire Spread Control Reasons for Fireground VentilationEffective ventilationReduces rate of smoke layer developmentCan reverse process of smoke layer developmentReduces ra

11、te at which fire will spread over area(Continued)13Fire Spread Control Reasons for Fireground VentilationEven with proper ventilation, if fire not extinguished soon after ventilation completed, increased supply of fresh air will feed fireVentilation should occur only after hoseline crews ready to mo

12、ve in, attack14Reduction of Flashover Potential Reasons for Fireground VentilationFlashoverTransition between growth, fully developed As unventilated interior fire burns and flames, smoke, and gases extend, heat radiates back down until combustibles heated to ignition temperaturesOnce ignition tempe

13、ratures reached, contents will ignite (Continued)15Reduction of Flashover Potential Reasons for Fireground VentilationVentilation helps prevent flashover from occurringOpening single door or window may not remove enough smoke, heat to prevent flashover(Continued)16Reduction of Flashover Potential Re

14、asons for Fireground VentilationIf fire producing significant amount of smoke and heat but limited by available oxygen, ventilating room may cause rapid ignition of hot fire gases in upper layer, initiating flashover17Reduction of Backdraft Potential Reasons for Fireground VentilationWhen fire confi

15、ned in compartment and does not break window or burn through to outside, will reduce oxygen level until flaming combustion no longer possibleIf air supply introduced, backdraft occurs(Continued)18Reduction of Backdraft Potential Reasons for Fireground VentilationTo prevent backdraft conditions, care

16、fully controlled ventilation must be providedVertical ventilation often safest for thisSigns of potential backdraft19Property Conservation Reasons for Fireground VentilationRapid extinguishment reduces water, heat, smoke damageTimely, effective ventilation helps extinguish interior fires fasterSmoke

17、 may be removed from buildings by natural or mechanical means(Continued)20Property Conservation Reasons for Fireground VentilationWhen smoke, gases, heat removed from burning building, fire can be confinedIf sufficient personnel, effective salvage operations can be initiated outside immediate fire a

18、rea during fire control operations21Considerations Affecting VentilationIs there need at this time?Where is ventilation needed?What type should be used?Do fire, structural conditions allow for safe roof operations?Are Vent Group personnel trained, equipped to ventilate building?22Life Safety Hazards

19、First consideration is safety of firefighters and building occupantsLife hazards in burning building generally lower if occupants awakeIf occupants asleep, a number of possibilities must be considered(Continued)23Life Safety HazardsDepending on fire conditions, ventilation may be needed before searc

20、h and rescue beginsHazards from accumulation of smoke, gases in building24Visible Smoke ConditionsSmoke accompanies most ordinary forms of combustionDensity of smoke increases with amount of suspended particlesSmoke conditions vary according to how burning has progressed25The Building InvolvedIn add

21、ition to location of fire within building, buildings age, type, design must be consideredOther factors include number and size of wall openings, type of roof construction, etc.(Continued)26The Building InvolvedIf results of preincident planning have been documented and are available to officers on f

22、ireground, may provide valuable information affecting ventilationHigh-rise buildings have extra considerations27Basements and Windowless BuildingsWithout effective ventilation, access into basement is difficult because firefighters must descend through worst heat, smoke to get to seatSeveral feature

23、s impede attempts at natural ventilation(Continued)28Basements and Windowless BuildingsMany buildings have windowless wall areasIn some cases, creating openings needed may delay operation considerablyVentilating considerations29Location and Extent of FireFirst-arriving units must determine size, ext

24、ent of fire as well as locationSeverity, extent of fire depend on number of factors(Continued)30Location and Extent of FirePhase to which fire has progressed is a primary consideration in selecting ventilation proceduresWays that vertical fire extension occurs31Selecting Place to VentilateIdeal situ

25、ation one with as much information as possible about fire, building, occupancyMany factors have bearing on where to ventilateMany considerations before ventilating building32Vertical VentilationOpening roof/existing roof openings for allowing heated gases, smoke to escapeFirefighters must understand

26、 basic types, designs of roofsFirefighters must know how roofs in the response areas are constructed(Continued)33Vertical Ventilation Preincident InspectionsIdentifyNew construction projectsExisting constructionUse of lightweight building materialsInformation that can alert firefighters34Likelihood

27、of Roof Collapse During Vertical VentilationBased onVolume of fireHow long fire has been burningType of constructionLevel of protectionLoad on roof35Responsibilities During Vertical Ventilation Officer in ChargeDetermine it can be done safely, effectivelyConsider age, type of constructionConsider lo

28、cation, duration, extent of fireObserve safety precautions(Continued)36Responsibilities During Vertical Ventilation Officer in ChargeIdentify escape routesSelect place to ventilateMove personnel, tools to roof37Responsibilities During Vertical Ventilation Leader on RoofEnsure roof safe to operate on

29、Ensure only required openings madeDirect efforts to minimize secondary damageCoordinate crews efforts with firefighters inside building(Continued)38Responsibilities During Vertical Ventilation Leader on RoofEnsure safety of all personnelEnsure team leaves roof as soon as assignment completed39Safety

30、 Precautions During Vertical VentilationCheck wind direction with relation to exposuresWork with wind at back/side to provide protection while cuttingNote existence of roof obstructions/excessive weight on roof(Continued)40Safety Precautions During Vertical VentilationProvide secondary means of esca

31、pe for crewsEnsure main structural components not cut while creating openingGuard opening to prevent personnel falling into it(Continued)41Safety Precautions During Vertical VentilationEvacuate roof promptly when ventilation completeUse lifelines, roof ladders, other means to prevent sliding/falling

32、Make sure roof ladder (if used) firmly secured over roofs peak(Continued)42Safety Precautions During Vertical VentilationExercise caution when working around electric, guy wiresEnsure all personnel on roof wear full PPE including SCBAKeep other firefighters out of range of those swinging axes, opera

33、ting saws(Continued)43Safety Precautions During Vertical VentilationCaution axe users to be aware of overhead obstructionsStart power tools on ground to ensure operation; shut off before hoisting/carrying to roofExtend ladders 3-5 rungs above roof line, secure ladder(Continued)44Safety Precautions D

34、uring Vertical VentilationWhen operating from aerial ladder platforms, floor of platform even with/slightly above roof levelCheck roof for structural integrity before stepping on, continue sounding throughout operation(Continued)45Safety Precautions During Vertical VentilationAlways walk on bearing

35、walls, strongest points of roof structureEnsure ceilings punched through to enhance ventilation46Unsafe Roof Warning SignsMelting asphalt Spongy RoofSmoke coming from roofFire coming from roof47Roof CoveringsPart of roof exposed to weatherTypesSome susceptible to ignition from sparks, burning embers

36、; others notSome have coating of insulating material48Existing Roof OpeningsSometimes used for vertical ventilationRarely in best location/large enoughUsually supplement cut holes(Continued)49Existing Roof OpeningsScuttle hatchesSkylightsMonitorsVentilating shaftsPenthouse/bulkhead doors50General Ve

37、ntilation Considerations for RoofsSquare/rectangular opening easier to cut, easier to repairOne large opening better than several small51Commonly found on commercial, industrial, apartment buildingsCommon on many single-family residencesFlat Roofs(Continued)52Flat RoofsMay/may not have slight slope

38、for drainageFrequently penetrated by chimneys, vent pipes, etc.May be surrounded and/or divided by parapets(Continued)53Flat RoofsMay support water tanks, HVAC equipment, etc.Structural partDeckingConstruction materials determine equipment necessary to ventilate54Pitched RoofsAmong most common are t

39、hose elevated in center along ridge with roof deck sloping down to eaves along roof edges(Continued)55Pitched RoofsShed roofs Pitched along one edge with deck sloping down to eaves at opposite edgeMost involve rafters/trussesHave more pronounced downward slope than flat; may be steep(Continued)56Pit

40、ched RoofsProcedures for opening similar to flat roofs; precautions must be taken to prevent slippingSome types may require different opening techniques57Arched RoofsCan span large open areas unsupported by pillars/postsOne type uses bowstring trusses(Continued)58Arched RoofsLamella or trussless arc

41、hed roofsProcedures for cutting ventilation openings same as flat/pitched except no ridge to hook roof ladders; curvature of roof prevents roof ladders from lying flat59Precast Concrete RoofsCan be fabricated off-siteAvailable in many shapes, sizes, designsSome use lightweight material(Continued)60P

42、recast Concrete RoofsLightweight usually finished with roofing felt and mopping of hot tarExtremely difficult to break throughExisting openings should be used for ventilation on heavy roofs61Poured-In Place Concrete RoofsSome lightweight concrete roof decks poured in place over permanent form boards

43、, steel roof decking, paper-backed mesh, or metal rib lath(Continued)62Poured-In Place Concrete RoofsRelatively easy to penetrateSome can be penetrated with hammer-head pick or power saw with concrete bladeHeavier roofs require jackhammer/diamond-tipped chain saw63Metal RoofsMade from several differ

44、ent kinds of metal; constructed in many styles(Continued)64Metal RoofsLight-gauge steel roof decks can be supported on steel frameworks/laid over existing roofLight-gauge cold-formed steel sheets used primarily for industrial buildings(Continued)65Metal RoofsExcept when covered with lightweight conc

45、rete, seldom covered with roofing materialMetal cutting tools/power saws with metal cutting blades must be used to open(Continued)66Metal RoofsOften penetrated by roof openingsOlder buildings may have roofs made of large pieces of sheet metal laid over skip sheathing67Trench Ventilation (Strip Venti

46、lation)Used to stop spread of fire in long, narrow structure(Continued)68Trench Ventilation (Strip Ventilation)Performed by cutting large opening at least 4 feet (1.2 m) wide extending from one exterior wall to opposite exterior wallOften, large ventilation opening is cut between trench cut and fire

47、69Conventional Basement VentilationIn absence of built-in vents from basement, heat and smoke from basement fires quickly spread upward(Continued)70Conventional Basement VentilationCan be accomplished several waysIf basement has ground-level windows, horizontal ventilation can be employedIf windows

48、unavailable, interior vertical ventilation must be performed71Factors Reducing Effectiveness of Vertical VentilationImproper use of forced ventilationIndiscriminant window breakingFire streams directed into ventilation openingsBreaking skylights(Continued)72Factors Reducing Effectiveness of Vertical

49、 VentilationExplosionsBurn-through of roof, floor, wallAdditional openings between attack team, upper ceiling73Horizontal VentilationVenting of heat, smoke, and gases through horizontal openingsCertain structures lend themselves to this application(Continued)74Horizontal VentilationMany aspects of v

50、ertical ventilation apply to horizontal ventilation; different procedure must be followedBesides direct flame contact, horizontal extension can occur in several ways75Horizontal Ventilation Considerations WeatherMust always be consideredWind has most potential influence; can aid or hinder horizontal

51、 ventilationWind direction Setting up natural horizontal ventilation76Horizontal Ventilation Considerations ExposuresInternal Include building occupants, any uninvolved rooms/portions of buildingExternal(Continued)77Horizontal Ventilation Considerations ExposuresBecause horizontal ventilation does n

52、ot release heat and smoke directly above fireRouting necessaryRoutes may be same needed for evacuationEffects on rescue, exit must be considered(Continued)78Horizontal Ventilation Considerations ExposuresBecause heat, smoke, fire can be discharged below highest point of buildingAlso danger that risi

53、ng gases will ignite portions of building above exit pointRising gases may be drawn into windows/attic vents above exit point(Continued)79Horizontal Ventilation Considerations ExposuresBecause heat, smoke, fire can be discharged below highest point of building (cont.)They may ignite eaves of buildin

54、g/adjacent structuresUnless for rescue, building should NOT be ventilated until charged hoselines in place at entry pointCharged hoselines should be ready at intermediate point where fire might spread(Continued)80Daylight Basement Ventilation ConsiderationsDaylight basementsOccur in homes built on s

55、lopesFinished basements with large exterior windows, possibly exterior door(s)Easier to ventilate than conventionalOpening door, breaking windows, etc. provides adequate ventilation81Precautions Against Upsetting Horizontal VentilationOpening a door/window on windward side of building prior to venti

56、lation exit opening on leeward size may pressurize building, intensify fire, cause fire spreadTake advantage of air currentsIf established currents blocked, positive effects may be reduced/eliminated82Advantages of Forced VentilationSupplements, enhances natural ventilationEnsures more control of ai

57、r flowSpeeds removal of contaminantsReduces smoke damagePromotes good public relations83Disadvantages of Forced VentilationMay cause fire to intensify, spreadDepends on power sourceRequires special equipment84Negative-Pressure Ventilation (NPV)Oldest type of mechanical forced ventilation techniques

58、Using fans to develop artificial circulation/enhance natural ventilationFans placed in windows, doors, roof vent openings to exhaust smoke, heat, gases(Continued)85Negative-Pressure Ventilation (NPV)NPV operationsFan should be positioned to exhaust in same direction as prevailing windTechnique uses

59、wind to supply fresh air If prevailing wind too light, fans can be positioned on windward side of structure to blow air into building(Continued)86Negative-Pressure Ventilation (NPV)If open areas around smoke ejector not properly sealedAir can recirculate into buildingAtmospheric pressure pushes air

60、back through spaces; smoke reenters roomTo prevent recirculation, cover area around fan(Continued)87Negative-Pressure Ventilation (NPV)Flow of smoke, other gases to exit opening should be kept straight as possibleAvoid opening windows near exhaust fan because this can reduce efficiencyRemove all obs