14 Ventilation

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.

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.

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.

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.

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

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.

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

Benefits of Proper Ventilation (2 of 2)

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.

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

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.

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

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

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

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

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

Ordinary Construction (2 of 2) Paths of fire spread Plumbing and electrical chases Void spaces in walls Cockloft © Steven Townsend/Code 3 Images.

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

Ventilation and Tactical Priorities Ventilation is directly related to tactical priorities. Courtesy of District Chief Chris E. Mickal/New Orleans Fire Department, Photo Unit.

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

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

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

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

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 Courtesy of Chris E. Mickal/New Orleans Fire Department, Photo Unit.

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

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

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

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

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.

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

Mechanical Ventilation Methods of mechanical ventilation Negative-pressure Positive-pressure Hydraulic

Negative-Pressure Ventilation Ejectors Limitations: Positioning Power source Maintenance Air flow control Advantages Explosion-proof motors Courtesy of Super Vacuum Mfg. Co., Inc.

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

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

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

Vertical Ventilation (2 of 2) Make opening close to seat of fire Determine hottest point Courtesy of Captain David Jackson, Saginaw Township Fire Department.

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.

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

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

Roof Construction Two components Support structure Roof covering 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

Types of Roof Failures Support system failure Roof covering 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

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

Roof Designs (1 of 2) Flat roofs Pitched 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

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 Courtesy of Captain David Jackson, Saginaw Township Fire Department.

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

Vertical Ventilation Assessment (1 of 2) Construction features Indications of fire damage Safety zones and exit paths Built-in roof openings Courtesy of Four Seasons Solar Products, LLC.

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'

Tools Used in Vertical Ventilation Power saws Axes Halligan tools Pry bars Tin cutters Pike poles, other types of hooks Utility rope

Types of Roof Cuts Rectangular cut Louver cut Triangular cut Peak cut Trench cut

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

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

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.

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.

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

Special Considerations Obstacles preventing ventilation Concrete roofs Metal roofs Basement fires High-rise buildings Windowless buildings Large buildings

Obstacles to Ventilation Poor access Multiple roofs and roof layers Sealed and boarded abandoned buildings Security measures such as steel bars and shutters

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

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.

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

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.

Stack Effect Smoke Patterns

Windowless Buildings Traps heat and smoke Treat similar to a basement fire. Ventilate high. © olaf schlueter/ShutterStock, Inc.

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.

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.

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.

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.