Understanding Fire Ventilation: Principles, Benefits, and Safety Measures

1. 14 Ventilation

2. Objectives (1 of 4) • 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.

3. Objectives (2 of 4) • Describe how building construction features within a structure affect ventilation. • List the principles, advantages, limitations, and effects of horizontal ventilation. • List the principles, advantages, limitations, and effects of natural ventilation.

4. Objectives (3 of 4) • List the principles, advantages, limitations, and effects of mechanical ventilation. • List the principles, advantages, limitations, and effects of negative-pressure and positive-pressure ventilation. • List the principles, advantages, limitations, and effects of hydraulic ventilation.

5. Objectives (4 of 4) • List the principles, advantages, limitations, and effects of vertical 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.

6. 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

7. 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.

8. Benefits of Proper Ventilation (1 of 2) • Locate trapped occupants faster • Fresh air to occupants • Advance hose lines more rapidly and safely • Reduce backdraft and flashover • Limit fire spread • Reduce property loss

9. Benefits of Proper Ventilation (2 of 2)

10. Backdraft (1 of 2) • Occurs when building is charged with hot gases and oxygen has been consumed • When air is introduced, fuel can ignite and explode.

11. Backdraft (2 of 2) • Release heat and unburned particles without allowing entry of clean air. • Ventilate as high as possible.

12. Flashover • Needs both ventilation and cooling • Occurs when • Air in room is very hot. • All combustibles in the space are near their ignition point. • Applying water cools the atmosphere. • Ventilation draws the heat and flames away.

13. Factors Affecting Ventilation (1 of 2) • Convection • Heated gases will always follow the path of least resistance. • Use this basic principle to cause the convection flow to draw heated products out of the building. • Mechanical ventilation activities • Negative-pressure • Positive-pressure • Hose streams

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

15. Building Construction Considerations • The way a building is constructed will affect ventilation operations.

16. Fire-Resistive Construction • Construction design • Structural components noncombustible • Compartmentalization • Paths of fire spread • Heating, cooling, plumbing, electrical • Elevator shafts • Stairwells • Roofs generally steel or concrete

17. Ordinary Construction (1 of 2) • Construction design • Exterior walls noncombustible • Interior walls/floors of wood • Roof is wood decking and structural support.

18. Ordinary Construction (2 of 2) • Paths of fire spread • Plumbing and electrical chases • Void spaces in walls • Cockloft

19. Wood-Frame Construction • Exterior walls are combustible • Paths of fire spread • Attics and cocklofts • Wood truss roofs and floors • Construction types • Balloon-frame • Platform

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

21. 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

22. Venting for Containment • Second highest priority is contain the fire and control the situation. • Prevents fire spread • Makes fire attacks easier

23. Venting for Property Conservation • Can significantly limit property damage • Rapid ventilation reduces damage from smoke, heat, and water.

24. Location and Extent of Smoke and Fire Conditions–Fire Fighter II Standard (1 of 3) • Factors to consider • Size of the fire • Stage of combustion • Location within the building • Available ventilation options

25. Location and Extent of Smoke and Fire Conditions–Fire Fighter II Standard (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 (toward ventilation opening).

26. Location and Extent of Smoke and Fire Conditions–Fire Fighter II Standard (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-based fire • Cool days may cause smoke inversion. • Sprinkler activation may cause the smoke to cool and act as a fog.

27. 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

28. Horizontal Ventilation (1 of 2) • Commonly used in residential fires and room-and-contents fires • Generally fast and easy to use • Can be used from inside or outside the building

29. 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

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

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

32. Breaking Glass (1 of 2) • General rules • Try to open first. • Wear full protective clothing and eye protection.

33. Breaking Glass (2 of 2) • General rules (continued) • 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.

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

35. Mechanical Ventilation • Methods of mechanical ventilation • Negative-pressure • Positive-pressure • Hydraulic

36. Negative-Pressure Ventilation • Ejectors • Limitations: • Positioning • Power source • Maintenance • Air flow control • Advantages • Explosion-proof motors

37. Positive-Pressure Ventilation • Large, powerful fans • Advantages: • Quick and efficient • Increased safety • Disadvantages • May spread the fire • May increase carbon monoxide levels

38. Hydraulic Ventilation • Fog or broken pattern • Advantages • Move several thousand cubic feet of air per minute • Disadvantages • Water damage • Safety hazards

39. Vertical Ventilation (1 of 2) • Releases combustion products vertically • Occurs naturally if there is an opening • May be assisted by mechanical means

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

41. Safety Considerations (1 of 2) • Structural stability of the roof • Falling from the roof • Two exit routes • Opening should not be between fire fighters and exit. • Have a charged hose line ready. • Leave the area once done.

42. 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

43. 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

44. 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 weather-resistant materials • Supported by the roof decking

45. Types of Roof Failures • Support system failure • Supporting structure fails • Often a sudden and total collapse • Roof covering failure • Burns through roof covering • Spreads out causing roof failure • In warmer climates burn through quickly; in colder climates burn with little evidence

46. Solid Beam vs. Truss • Solid beam • Girders, beams, and rafters • Truss • Lightweight components • Wood or steel bars • Triangular configuration

47. 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 • Type of construction dictates how to ventilate

48. Roof Designs (2 of 2) • Arched roofs • Generally found in commercial structures to create a large span without columns • Use bowstring trusses in which fire can severely and quickly weaken structure

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

50. Vertical Ventilation Assessment (1 of 2) • Construction features • Indications of fire damage • Safety zones and exit paths • Built-in roof openings