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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.