ventilation
DESCRIPTION
TS 10 –1. VENTILATION. The systematic removal of heated air, smoke, and gases from a structure and replacement with cooler, cleaner air. TS 10 –2. TYPES OF VENTILATION. Vertical Trench (strip) Basement Horizontal Natural Forced Mechanical positive-pressure - PowerPoint PPT PresentationTRANSCRIPT
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VENTILATION
The systematic removal of heated air, smoke, and gases from a structure and replacement
with cooler, cleaner air
TS 10–1
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TYPES OF VENTILATION
• Vertical – Trench (strip)– Basement
• Horizontal – Natural– Forced
• Mechanical positive-pressure• Mechanical negative-pressure• Hydraulic
TS 10–2
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WHY VENTILATE?
• Aids in saving lives
• Aids in suppressing fire
• Aids in reducing property damage
TS 10–3
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TODAY’S INCREASING NEED FOR VENTILATION
• Increased fuel load in all occupancies due to increased use of plastics and other synthetic materials
• More products of combustion
• More dangerous products of combustion
• “Tighter” homes making heat retention greater– Increased insulation– Energy-saving glass– Vapor barriers
TS 10–4
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ADVANTAGES OF VENTILATION TO RESCUE OPERATIONS
• Improves visibility
• Allows for faster location of unconscious victims
• Simplifies and expedites rescue
• Makes conditions safer for firefighter and victims
TS 10–5
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ADVANTAGES OF VENTILATION TO FIRE ATTACK & EXTINGUISHMENT
• Removes smoke, gases, and heat from building
• Facilitates entry of firefighters
• Reduces obstacles that hinder firefighters
• Increases visibility for quicker location of seat of fire
TS 10–6
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ADVANTAGES OF VENTILATION TO FIRE CONTROL
• Reduces mushrooming
• Reduces flashover potential
• Reduces backdraft potential
• Controls fire spread
TS 10–7
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ADVANTAGES OF VENTILATION TO PROPERTY CONSERVATION
• Permits rapid extinguishment
• Reduces water, heat, and smoke damage
• Confines fire to an area
• Allows salvage operations and fire control to take place concurrently
TS 10–8
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BACKDRAFT INDICATIONSVS 10-2
PuffingSmoke
Black SmokeBecoming Dense
Yellow-Gray
Walls TooHot to Touch
Dull Orange Glowof Visible Fire
PressurizedSmoke Coming
From SmallCracks
Darkened Windows
Rattling Windows
Hot UnbrokenGlass
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BACKDRAFT PREVENTION
Top (vertical) ventilation is the primary method
of preventing backdraft.
TS 10–9
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LIFE SAFETY HAZARDS IN UNVENTILATED BUILDINGS• Obscurity caused by dense smoke
• Presence of toxic gases
• Lack of oxygen
• Presence of flammable gases
• Danger of backdraft
• Danger of flashover and rollover
TS 10–11
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FACTORS DETERMINING HORIZONTAL OR VERTICAL
VENTILATION • Building type and design
• Number and size of wall openings
• Number of stories
• Number of staircases, shafts, dumbwaiters, ducts, roof openings
• Availability of exterior fire escapes
• Exposure involvement
TS 10–12
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VENTILATION PROBLEMS: BASEMENTS
VS 10-4
• Need to Descendthrough Heat andSmoke
• Blocked or Secured Outside Entrances
• Difficulty of UsingNatural Ventilation
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VENTILATION PROBLEMS: WINDOWLESS BUILDINGS
VS 10-5
• Late Detection DelayingVentilation and Creating Backdraft Conditions
• Horizontal VentilationDifficult or Impractical
• Usually Require Mechanical Ventilation
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VERTICAL FIRE EXTENSION
Opening for ventilation purposes before the fire is located may spread the fire to areas
that otherwise would not have been affected.
TS 10–13
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VENTILATION OPENING LOCATION & SIZE FACTORS
• Availability of natural openings
• Fire location
• Building construction
• Wind direction
• Fire phase
• Building condition
• Building contents
TS 10–15
• Roof type and condition
• Effects on fire
• Effects on exposures
• Attack crew’s readiness
• Ability to protect exposures
• Size
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VERTICAL VENTILATIONVS 10-6
Roof Opening(At least 4’ x 4’[1.2 m x 1.2 m])
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VERTICAL VENTILATION
Opening the roof or existing roof openings to allow heated gases and smoke to escape
to the atmosphere
TS 10–16
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PRE-VENTILATION SAFETY PRECAUTIONS
• Consider type of building involved.
• Consider location, duration, and extent of fire.
• Observe safety precautions.
• Identify escape routes.
• Select place to ventilate.
• Move personnel and tools safely to roof.
TS 10–17
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ROOF TYPESVS 10-7
FlatMansard
Shed
ButterflyHip
Gable
Lantern GambrelArch
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BASEMENT FIRES
• First extension commonly into the attic
• May be ventilated in a variety of ways:– Horizontal ventilation through ground-level
or below-ground windows – Through interior vertical shafts (stairwells,
hoistway shafts, etc.)– Mechanical ventilation through a hole in the
floor near a ground-level door or window
TS 10–29
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ELEVATED STREAMS
• Can force air and gases back into building if not used properly
• If projected just above the horizontal plane, are effective in subduing sparks and flying brands rising from ventilation opening and in reducing heat of thermal column
• Should never be projected through the ventilation hole while firefighters are still inside building
TS 10–30
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VENTILATIONVS 10-13
Correct Application
Incorrect Application
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FACTORS THAT CAN DESTROY VERTICAL VENTILATION
EFFECTIVENESS• Improper use of
forced ventilation
• Excess glass breakage
• Fire streams directed into ventilation holes
• Skylight breakage
TS 10–31
• Explosions
• Burn-through of the roof, floor, or wall
• Additional openings between attack team and upper opening
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HORIZONTAL VENTILATIONVS 10-14
Windward
Wind Direction
Leeward
Fresh Air
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HORIZONTAL VENTILATION
Venting of heat, smoke, and gases through wall openings such as windows and doors
TS 10–32
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HOW HORIZONTAL FIRE EXTENSION OCCURS
• Through wall openings by direct flame contact or by convected air
• Through corridors, halls, or passageways by convected air currents, radiation, and flame contact
• Through open space by radiated heat or convected air currents
TS 10–34
• In all directions by explosion or flash burning of fire gases, flammable vapors, or dust
• Through walls and interior partitions by direct flame contact
• Through walls by heat conduction through beams, pipes, or other objects that extend through walls
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HORIZONTAL EXTENSION KEY POINTS
• Wind is helpful but too much wind can be detrimental.– Windward — Side of building the wind is striking– Leeward — Opposite side of building
• Horizontal ventilation may block escape of occupants.
• There is an ignition hazard to higher portions of the fire building posed by rising heated gases.
TS 10–35a
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HORIZONTAL EXTENSION KEY POINTS (cont.)
• Do not open building until charged lines are in place at attack entrance point, where fire might be expected to spread, and in positions to protect exposures.
• Take precautions against upsetting horizontal ventilation.– First open a door on leeward side to create a normal
process of thermal layering.– Know that opening doors between fire fighting crews
and exit point reduces intake of fresh air.
TS 10–35b
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UPSETTING HORIZONTAL VENTILATION
VS 10-15
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FORCED VENTILATION
Ventilation accomplished mechanically (with fans) or hydraulically
(with fog streams)
TS 10–36
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PORTABLE FAN SAFETY MEASURES
• Shut down before moving.
• Carry by handles.
• Clear personnel from area before starting.
• Do not place where clothing, draperies, or curtains can be drawn into fan.
• Avoid the discharge stream: heat and particles may be projected by venting equipment.
TS 10–37
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ADVANTAGES OF FORCED VENTILATION
• Ensures more positive control of fire
• Supplements natural ventilation
• Speeds removal of contaminants
• Reduces smoke damage
• Promotes good public relations
TS 10–38
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DISADVANTAGES OF FORCED VENTILATION
• May cause fire to intensify and spread
• Depends upon a power source
• Requires special equipment
TS 10–39
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TYPES OF FORCED VENTILATION
VS 10-16
Positive Pressure Horizontal Mechanical Hydraulic
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FORCED VENTILATION MECHANICAL NEGATIVE PRESSURE
VS 10-17
Wind DirectionIntake
Opening(Optional
In-BlowingEjector)
Draft Path
Pressure Inside BuildingLower Than Outside Building
Smoke Ejector
(Exhaust)
Salvage CoverOr Tarp
BlockingOpening
Around Ejector
Closed Doors
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FORCED VENTILATION MECHANICAL POSITIVE PRESSURE
VS 10-18
ClosedDoors
High Power
Fan
ExitOpening
(Same Size AsEntry Opening)
Draft Path
Pressure Inside BuildingHigher Than
Outside Building
Cone CoveringEntire Door
Opening
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ADVANTAGES OF MECHANICAL POSITIVE-PRESSURE
VENTILATION• No need to enter smoke-filled environment
• Effectively supplements both horizontal and vertical ventilation
• Allows for efficient removal of smoke and heat
• Does not effect building contents or smoldering debris
• Is faster than negative-pressure ventilation
TS 10–40a
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ADVANTAGES OF MECHANICAL POSITIVE-PRESSURE VENTILATION (cont.)
• Does not interfere with ingress or egress
• Is easier to clean and maintain positive-pressure than negative-pressure fans
• Is applicable for all types of structures
• Allows for directing heat and smoke away from unburned areas or paths of exit
TS 10–40b
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DISADVANTAGES OF MECHANICAL POSITIVE-PRESSURE VENTILATION
• Requires an intact structure
• May increase interior levels of carbon monoxide
• May extend hidden fires
TS 10–41
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GUIDELINES FOR EFFECTIVE POSITIVE-PRESSURE VENTILATION
• Take advantage of existing wind conditions.
• Make certain that cone of air from fan covers the entire entry opening.
• Systematically open and close doors or increase the number of fans to reduce size of area being pressurized.
• Keep size of exit opening in proportion to the entry opening.
TS 10–42
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FORCED VENTILATION HYDRAULIC
VS 10-19
Fog Stream(Covering 85% 90% of Opening
Nozzle Tip(At least 2 ft. [0.6m]Back from Opening)
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HYDRAULIC VENTILATION• Typically used to clear a structure of heat, smoke,
steam, and gases following the initial knockdown of fire
• Takes advantage of air that is drawn into the fog stream to help push the products of combustion out of structure
• Fog pattern should be wide enough to cover 85 to 90 percent of the window or door opening through which the smoke will be pushed
• Nozzle tip should be no closer than 2 feet (0.6 m) from ventilation opening
TS 10–43
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DISADVANTAGES OF HYDRAULIC VENTILATION
• May increase amount of water damage
• Will put a drain on available water supply
• In freezing temperatures, will increase ice in area surrounding building
• Requires nozzle firefighters to remain in heated, contaminated atmosphere throughout operation
• Operation may be interrupted if nozzle team has to leave the area
TS 10–44
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