Transcript VENTILATION - Wellington County Training Officers Association

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
• Mechanical negative-pressure
• Hydraulic
TS 10–3
WHY VENTILATE?
• Aids in saving lives
• Aids in suppressing fire
• Aids in reducing property damage
TS 10–4
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 10–5
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 10–6
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 10–7
ADVANTAGES OF VENTILATION TO
FIRE CONTROL
• Reduces mushrooming
• Reduces flashover potential
• Reduces backdraft potential
• Controls fire spread
TS 10–8
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
VS 10-2
BACKDRAFT INDICATIONS
Puffing
Smoke
Black Smoke
Becoming Dense
Yellow-Gray
Walls Too
Hot to Touch
Dull Orange Glow
of Visible Fire
Pressurized
Smoke Coming
From Small
Cracks
Darkened
Windows
Rattling
Windows
Hot Unbroken
Glass
TS 10–9
BACKDRAFT PREVENTION
Top (vertical) ventilation is the primary
method
of preventing backdraft.
TS 10–11
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
FACTORS DETERMINING
HORIZONTAL OR VERTICAL
VENTILATION
TS 10–12
• 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
VENTILATION PROBLEMS:
BASEMENTS
• Need to Descend
through Heat and
Smoke
• Blocked or
Secured Outside
Entrances
• Difficulty of Using
Natural Ventilation
VS 10-4
VENTILATION PROBLEMS:
WINDOWLESS BUILDINGS
• Late Detection Delaying
Ventilation and Creating
Backdraft Conditions
• Horizontal Ventilation
Difficult or Impractical
• Usually Require
Mechanical Ventilation
VS 10-5
TS 10–13
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 10–15
VENTILATION OPENING
LOCATION & SIZE FACTORS
• Availability of natural
openings
• Roof type and
condition
• Fire location
• Effects on fire
• Building construction
• Effects on
exposures
• Wind direction
• Fire phase
• Building condition
• Building contents
• Attack crew’s
readiness
• Ability to protect
exposures
VERTICAL VENTILATION
Roof Opening
(At least 4’ x 4’
[1.2 m x 1.2 m])
VS 10-6
TS 10–16
VERTICAL VENTILATION
Opening the roof or existing roof openings
to allow heated gases and smoke to escape
to the atmosphere
TS 10–17
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.
ROOF TYPES
Flat
VS 10-7
Mansard
Shed
Butterfly
Hip
Lantern
Gambrel
Gable
Arch
TS 10–29
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 10–30
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
VS 10-13
VENTILATION
Correct Application
Incorrect Application
TS 10–31
FACTORS THAT CAN DESTROY
VERTICAL VENTILATION
EFFECTIVENESS
• Improper use of
forced ventilation
• Excess glass
breakage
• Fire streams
directed into
ventilation holes
• Explosions
• Burn-through of the roof,
floor, or wall
• Additional openings
between attack team and
upper opening
VS 10-14
HORIZONTAL VENTILATION
Wind Direction
Leeward
Windward
Fresh Air
TS 10–32
HORIZONTAL VENTILATION
Venting of heat, smoke, and gases through
wall openings such as windows and doors
TS 10–34
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
• 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,
TS 10–35a
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 10–35b
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.
UPSETTING HORIZONTAL
VENTILATION
VS 10-15
TS 10–36
FORCED VENTILATION
Ventilation accomplished mechanically
(with fans) or hydraulically
(with fog streams)
TS 10–37
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 10–38
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 10–39
DISADVANTAGES OF
FORCED VENTILATION
• May cause fire to intensify and spread
• Depends upon a power source
• Requires special equipment
TYPES OF FORCED
VENTILATION
Positive Pressure
Horizontal Mechanical
VS 10-16
Hydraulic
VS 10-17
FORCED VENTILATION MECHANICAL
NEGATIVE PRESSURE
Intake
Opening
(Optional
In-Blowing
Ejector)
Wind Direction
Closed
Doors
Smoke
Ejector
(Exhaust)
Draft Path
Pressure Inside Building
Lower Than Outside Building
Salvage Cover
Or Tarp
Blocking
Opening
Around Ejector
VS 10-18
FORCED VENTILATION
MECHANICAL POSITIVE PRESSURE
High
Power
Fan
Closed
Doors
Exit
Opening
(Same Size As
Entry Opening)
Draft Path
Pressure Inside Building
Higher Than
Outside Building
Cone Covering
Entire Door
Opening
TS 10–40a
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 10–40b
ADVANTAGES OF MECHANICAL
POSITIVE-PRESSURE
VENTILATION (cont.)
• Does not interfere with ingress or egress
• Is easier to clean and maintain positivepressure 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
DISADVANTAGES OF
MECHANICAL POSITIVEPRESSURE VENTILATION
• Requires an intact structure
• May increase interior levels of carbon
monoxide
• May extend hidden fires
TS 10–41
TS 10–42
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.
FORCED VENTILATION
HYDRAULIC
Fog Stream
(Covering 85%
90% of Opening
Nozzle Tip
(At least 2 ft. [0.6m]
Back from Opening)
VS 10-19
TS 10–43
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 10–44
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