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1 14 Ventilation 14 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. 14 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. 14 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. 14 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. 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 14 Introduction • Primary method of fire spread is convection. • Mushrooming occurs when the products of combustion reach the highest point. • Products of combustion present a risk. (2 of 2) 14 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 14 Benefits of Proper Ventilation (2 of 2) 14 Backdraft • Occurs when building is charged with hot gases and oxygen has been consumed • When air is introduced, fuel can ignite and explode. (1 of 2) 14 Backdraft • Release heat and unburned particles without allowing entry of clean air. • Ventilate as high as possible. (2 of 2) 14 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. 14 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 14 Building Construction Considerations • The way a building is constructed will affect ventilation operations. 14 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 14 Ordinary Construction (1 of 2) • Construction design – Exterior walls noncombustible – Interior walls/floors of wood – Roof is wood decking and structural support. 14 Ordinary Construction • Paths of fire spread – Plumbing and electrical chases – Void spaces in walls – Cockloft (2 of 2) 14 Wood-Frame Construction • Exterior walls are combustible • Paths of fire spread – Attics and cocklofts – Wood truss roofs and floors • Construction types – Balloon-frame – Platform 14 Ventilation and Tactical Priorities • Ventilation is directly related to tactical priorities. 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 14 Venting for Containment • Second highest priority is contain the fire and control the situation. • Prevents fire spread • Makes fire attacks easier 14 Venting for Property Conservation • Can significantly limit property damage • Rapid ventilation reduces damage from smoke, heat, and water. 14 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 14 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). 14 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—petroleumbased fire – Cool days may cause smoke inversion. – Sprinkler activation may cause the smoke to cool and act as a fog. 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 14 Horizontal Ventilation • 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 (1 of 2) 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 14 Methods of Ventilation • Natural – Depends on convection currents, wind, and other natural air movement • Mechanical – Uses mechanical means to augment natural ventilation 14 Natural Ventilation • Used when air currents are adequate • Used when ventilation is needed quickly • Open leeward side of building first, then windward. 14 Breaking Glass • General rules – Try to open first. – Wear full protective clothing and eye protection. (1 of 2) 14 Breaking Glass • 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. (2 of 2) 14 Opening Doors • • • • Provide large openings. May compromise entry/exit points May be best for clean air points Good location for mechanical ventilation devices 14 Mechanical Ventilation • Methods of mechanical ventilation – Negative-pressure – Positive-pressure – Hydraulic 14 Negative-Pressure Ventilation • Ejectors • Limitations: – – – – Positioning Power source Maintenance Air flow control • Advantages – Explosion-proof motors 14 Positive-Pressure Ventilation • Large, powerful fans • Advantages: – Quick and efficient – Increased safety • Disadvantages – May spread the fire – May increase carbon monoxide levels 14 Hydraulic Ventilation • Fog or broken pattern • Advantages – Move several thousand cubic feet of air per minute • Disadvantages – Water damage – Safety hazards 14 Vertical Ventilation • Releases combustion products vertically • Occurs naturally if there is an opening • May be assisted by mechanical means (1 of 2) 14 Vertical Ventilation • Make opening close to seat of fire • Determine hottest point (2 of 2) 14 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. 14 Safety Considerations • “Sound” the roof • Walk on areas of greatest support • Make cuts from – Upwind – With clear exit path – While standing on firm section (2 of 2) 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 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 weather-resistant materials • Supported by the roof decking 14 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 14 Solid Beam vs. Truss • Solid beam – Girders, beams, and rafters • Truss – Lightweight components – Wood or steel bars – Triangular configuration 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 • Type of construction dictates how to ventilate 14 Roof Designs • 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 (2 of 2) 14 Objectives of Vertical Ventilation • Provide the largest opening • Put in an appropriate location • Use the least amount of time • Use the safest technique 14 Vertical Ventilation Assessment (1 of 2) • Construction features • Indications of fire damage • Safety zones and exit paths • Built-in roof openings 14 Vertical Ventilation Assessment (2 of 2) • 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' 14 Tools Used in Vertical Ventilation • • • • • • • Power saws Axes Halligan tools Pry bars Tin cutters Pike poles, other types of hooks Utility rope 14 Types of Roof Cuts • • • • • Rectangular cut Louver cut Triangular cut Peak cut Trench cut 14 Rectangular 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 triangular cut to help pry up • If several layers exist, may have to peel a layer at a time 14 Louver 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 14 Triangular 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. 14 Peak 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. 14 Trench Cut • Used as a defensive tactic to stop the progress of a large fire in a narrow building • Creates a large opening ahead of the fire • “Writes off” part of the building • Requires both time and manpower 14 Special Considerations • • • • • • • Obstacles preventing ventilation Concrete roofs Metal roofs Basement fires High-rise buildings Windowless buildings Large buildings 14 Obstacles to Ventilation • • • • Poor access Multiple roofs and roof layers Sealed and boarded abandoned buildings Security measures such as steel bars and shutters 14 Ventilating a Concrete Roof • Found in commercial and industrial structures • Generally flat and hard to breach • May collapse from weakened support systems when exposed to fire • Search for alternative openings 14 Ventilating a Metal Roof • Discoloration and warping may indicate seat of fire. • As fire heats the metal deck, tar roof covering can melt and leak into the building. • Metal can roll down and create a dangerous slide directly into the opening. 14 Venting a Basement • Usually few windows • Usually requires both horizontal and vertical ventilation • Fire fighters must descend the stairs through the venting combustion products. • Make as many openings on one side and allow fire fighters to enter from the other 14 High-Rise Buildings • Many have hard to break sealed windows. • Unique smoke patterns with stack effect. • Newer buildings have smoke management in the HVAC. • Designate one stairwell as a rescue route. • Positive-pressure fans can keep smoke out of the stairs. 14 Stack Effect Smoke Patterns 14 Windowless Buildings • Traps heat and smoke • Treat similar to a basement fire. • Ventilate high. 14 Large Buildings • More difficult than small ones • Smoke cools as it travels, causing stratification. • When possible, use interior walls and doors to create smaller areas. 14 Summary • • • • (1 of 3) Ventilation provides many benefits. Several factors affect ventilation. Building construction affects ventilation. Ventilation is related to life safety, fire containment, and property conservation. 14 Summary (2 of 3) • Assessing the location and extent of smoke and fire will determine ventilation. • The types of ventilation are horizontal and vertical. • Horizontal ventilation uses horizontal openings in a structure. 14 Summary (3 of 3) • Vertical ventilation refers to the release of heat and smoke in a vertical direction. • Many obstacles can be encountered during ventilation operations. • Ventilation is a major consideration in backdraft and flashover.