Ventilation

1. Ventilation

2. 14 Objectives (1 of 3) • Define ventilation as it relates to fire suppression activities. • List the effects of properly performed ventilation on fire and fire suppression activities. • Describe how fire behavior principles affect ventilation. • Describe how building construction features within a structure affect ventilation.

3. 14 Objectives (2 of 3) • Define horizontal ventilation. • List the principles, advantages, limitations, and effects of horizontal ventilation. • List the principles, advantages, limitations, and effects of vertical ventilation. • List the principles, advantages, limitations, and effects of natural ventilation. • List the principles, advantages, limitations, and effects of mechanical ventilation.

4. 14 Objectives (3 of 3) • List the principles, advantages, limitations, and effects of positive-pressure and negative-pressure ventilation. • List the principles, advantages, limitations, and effects of hydraulic ventilation. • List safety precautions for ventilating roofs. • List the basic indicators of roof collapse. • Explain the role of ventilation in the prevention of backdraft and flashover.

5. 14 Introduction (1 of 2) • Ventilation • The process of removing smoke, heat, and toxic gases from a burning building and replacing them with cooler, cleaner, more oxygen-rich air

6. 14 Introduction (2 of 2) • Primary method of fire spread is convection • Mushrooming occurs when the products of combustion reach the highest point. • Products of combustion present a risk to fire fighters and occupants.

7. 14 Benefits of Proper Ventilation (1 of 2) • Locate trapped occupants faster • Fresh air to occupants overcome by smoke • Advance hose lines more rapidly and safely • Reduce backdraft and flashover • Limits fire spread • Reduces property loss

8. 14 Benefits of Proper Ventilation (2 of 2) Unvented structure Vented structure

9. 14 Factors Affecting Ventilation (1 of 2) • Convection currents • Mechanical ventilation activities • Negative-pressure • Positive-pressure • Hose streams

10. 14 Factors Affecting Ventilation (2 of 2) • Wind and atmospheric forces • Wind speed and direction • Temperature and humidity

11. 14 Building Construction • The way a building is constructed will affect ventilation operations.

12. 14 Fire-Resistive Construction • Construction design • Structural components noncombustible • Compartmentalization • Paths of fire spread • Heating, Ventilation, and Air Conditioning • Stairways • Elevator shafts • Roofs generally of steel or concrete

13. 14 Ordinary Construction • Construction design • Exterior walls noncombustible • Interior walls/floors of wood • Roof is wood decking and structural support • Paths of fire spread • Plumbing and electrical chases • Void spaces in walls • Cockloft

14. 14 Wood-Frame Construction • Construction design • Similar to ordinary but exterior walls are combustible • Paths of fire spread • Attics and cocklofts • Wood truss roofs and floors • Construction types • Balloon-frame • Platform

15. 14 Ventilation and Tactical Priorities • Ventilation is directly related to tactical priorities.

16. 14 Venting for Life Safety • Life safety is the primary goal. • Gives occupants a greater chance to survive • Makes searches faster • Limits fire spread to other occupants and fire fighters

17. 14 Venting for Confinement • Second highest priority is contain the fire and control the situation • Prevents fire spread • Makes fire attacks easier

18. 14 Venting for Property Conservation • Limits amount of damaged areas • Rapid removal limits amount of permanent damage.

19. 14 Location and Extent of Smoke and Fire Conditions (1 of 3) • Factors to consider • Size of the fire • Stage of combustion • Location within the building • Available ventilation options

20. 14 Location and Extent of Smoke and Fire Conditions (2 of 3) • Where to ventilate • As close to the fire as possible • Directly over the seat • Through an open door or window that opens outside • If unable to vent close to the fire • Predict how location will affect the fire • Anticipate fire spread and locate hose lines for protection

21. 14 Location and Extent of Smoke and Fire Conditions (3 of 3) • Determine fire size, intensity, and fuel • Light smoke, moving lazily—small fire of ordinary combustibles • Large amount of black rolling smoke—petroleum base fire • Hotter the fire, the faster the smoke moves • Cool days may cause smoke inversion. • Sprinkler activation may cause the smoke to cool and act as a fog.

22. 14 Types of Ventilation • Two basic types of ventilation • Horizontal • Utilizes horizontal openings in a structure such as doors and windows • Vertical • Involves openings in the roofs or floors

23. 14 Horizontal Ventilation (1 of 2) • Commonly used in • Residential fires • Room-and-contents fires • Fires that can quickly be controlled • Generally fast and easy to use • Can be used from inside or outside the building

24. 14 Horizontal Ventilation (2 of 2) • Most effective when opening is directly to outside • More difficult when there are no openings • Limits structural damage • May utilize natural and mechanical methods

25. 14 Methods of Ventilation • Natural • Depends on convection currents, wind, and other natural air movement • Mechanical • Uses mechanical means to augment natural ventilation

26. 14 Natural Ventilation • Used when air currents are adequate • Used when ventilation is needed quickly • Open leeward side of building first, then windward.

27. 14 Breaking Glass • General rules • Try to open first. • Wear full protective clothing and eye protection. • Ensure no one will be struck by the glass. • Always use a tool. • Keep hands above or to the side of the glass. • Use a tool to clear remaining glass.

28. 14 Opening Doors • Provide large openings • May compromise entry/exit points • May be best for fresh air points • Good location for mechanical ventilation devices

29. 14 Mechanical Ventilation • Methods of Mechanical Ventilation • Negative-pressure • Positive-pressure • Hydraulic

30. 14 Negative-Pressure Ventilation • Uses fans called ejectors to exhaust smoke and heat • Limitations: • Positioning • Power source • Maintenance • Air flow control • Advantages • Explosion-proof motors

31. 14 Positive-Pressure Ventilation • Uses large, powerful fans to force fresh air into a structure. • Advantages: • Quick and efficient • Increased safety • Disadvantages • May spread the fire • May increase carbon monoxide levels

32. 14 Hydraulic Ventilation • Uses a fog or broken pattern stream to create a pressure differential • Advantages • Can move several thousand cubic feet of air per minute • Does not require specialized equipment • Disadvantages • Water damage • Safety hazards

33. 14 Vertical Ventilation (1 of 2) • Releases combustion products vertically • Occurs naturally if there is an opening • May be assisted by mechanical means • Usually involves making openings in roof

34. 14 Vertical Ventilation (2 of 2) • Make opening close to seat of fire • Determine hottest point

35. 14 Safety Considerations (1 of 2) • Structural stability of the roof • Falling from the roof • Two exit routes • Not getting opening between you and the exit • Have a charged hose line • Leave the area once done

36. 14 Safety Considerations (2 of 2) • “Sound” the roof • Walk on areas of greatest support • Make cuts from • Upwind • With clear exit path • While standing on firm section

37. 14 Basic Indicators of Roof Collapse • Spongy feeling • Visible sagging • Roof separating from the walls • Structural failure in another portion of building • Sudden increase in fire intensity

38. 14 Roof Construction • Two components • Support structure • Solid beams of wood, steel, or concrete • System of trusses of wood, steel, or wood and steel • Roof covering • Made of various water repellant materials • Supported by the roof decking

39. 14 Types of Roof Failures • Support system failure • Supporting structure fails • Often a sudden and total collapse • Areas with heavy snow loads more prone • Roof covering failure • Burns through roof covering close to seat of fire • Spreads out causing roof failure • Areas with light snow loads more prone

40. 14 Solid Beam vs. Truss • May not be able to tell by looking • Solid beam • Girders, beams, and rafters • Truss • Lightweight components, often 2" x 4" wood with gussets or staples • Steel bars welded together • Triangular configuration

41. 14 Roof Designs (1 of 2) • Flat roofs • Can be constructed with many types of supports, decking, and materials • Pitched roofs • Have a visible slope for rain, ice, and snow runoff

42. 14 Roof Designs (2 of 2) • Arched roofs • Generally found in commercial structures to create a large span without columns

43. 14 Objectives of Vertical Ventilation • Provide the largest opening • Put in an appropriate location • Use the least amount of time • Use the safest technique

44. 14 Vertical Ventilation Assessment • Construction features • Indications of fire damage • Safety zones and exit paths • Built-in roof openings • Locate at highest point and over seat of fire • May need to cut an examination hole • One hole is better than several small ones • Minimum size 4' x 4'

45. 14 Tools Used in Vertical Ventilation • Power saws • Axes • Halligans • Pry bars • Tin cutters • Pike poles and other types of hooks • Utility rope

46. 14 Types of Roof Cuts • Rectangular cut • Louver cut • Triangle cut • Peak cut • Trench cut

47. 14 Rectangular or Square Roof Cut • Requires four cuts completely through the decking • Use care to not cut structural supports. • Stand upwind and have a safe exit. • Can use a triangle cut to help pry up • If several layers exist, may have to peel a layer at a time

48. 14 Louver Roof Cut • Used for flat or sloping roofs with plywood decking • Power saw or axe used to make the cuts • Can quickly create a large opening

49. 14 Triangle Roof Cut • Used to prevent metal decking from rolling away as it is cut • A saw or axe is used. • Several may be needed because of their small size.

50. 14 Peak Roof Cut • Used for peaked roofs with plywood sheeting • A tool is used to reveal the roof covering along the peak. • A power saw or axe is used to make a series of vertical cuts between the supports.