Transcript Ventilation Practices

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8-1.1 Define the principles of ventilation, and identify the
advantages and effects of ventilation.
8-1.2 Identify the dangers present, and the precautions to
be taken in performing ventilation.
8-1.3 Demonstrate opening various types of windows
from inside and outside, with and without fire department
tools.
8-1.4 Demonstrate breaking window or door glass, and
removing obstructions.
8-1.5 Using an axe, demonstrate the ventilation of a roof
and a floor.
8-1.6 Demonstrate ventilation using a water fog.
8-1.7 Define the theory of a back draft explosion.
8-1.8 Identify the signs of a potential flashover.
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8-2.1 Demonstrate the use of different types of
power saws and jack hammers.
8-2.2 Identify the different types of roofs,
demonstrate the techniques used to ventilate each
type, and identify the necessary precautions.
8-2.3 Identify the size and location of an opening
for ventilation, and the precautions to be taken
during ventilation.
8-2.4 Demonstrate the removal of skylights,
scuttle covers, and other covers on roof tops.
8-2.5 Demonstrate the types of equipment used
for forced mechanical ventilation.
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8-3.1 Identify and demonstrate natural and
mechanical methods for horizontal
ventilation of a structure.
8-3.2 Identify and demonstrate natural and
mechanical methods for vertical ventilation
of a structure.
8-3.3 Identify the location of the opening,
the methods to be used, and the
precautions to be taken when ventilating a
basement.
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Ventilation is the systematic removal and
replacement of heated air, smoke, and gases
from a structure, with cooler air
Ventilation facilitates entry by firefighters and
improves life safety for rescue and other
firefighting operations
Ventilation increases visibility, decreases
danger to trapped occupants by channeling
away hot, toxic gases, and it reduces the
chance of flashover or backdraft
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Because the increased use of plastics and other
synthetics have greatly increased the fuel load
in all occupancies, modern technology requires
a greater emphasis on ventilation
The products of combustion are becoming
more dangerous and are in larger quantities
than ever before
Prompt ventilation for the saving of lives,
suppression of fire, and reduction of damage is
just as important, if not more so, than it ever
has been
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Today’s energy conserving houses create
additional ventilation issues
Energy saving glass, steel entry doors, and
building vapor barriers make heat
retention much greater
This means when there is a fire, the heat is
retained better, and flashover can occur
faster than in a less insulated structure
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A roof covering is the exposed part of the
roof {the part we see every day} and its
purpose is to protect against the weather
It can be wood shingles, composition
shingles, composition roofing paper, tile,
slate, synthetic membrane, or built up tar and
gravel
This is important to us because it may be
subjected to sparks or blazing embers from
another source
Insulation over the covering retains heat and
may reduce fire rating drastically, causing
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All the preceding mean that the need for
ventilation is increased and it must be
accomplished much sooner than in the past
We must know how the roofs in our area are
constructed
Pre Incident plans need to note roof
construction and any areas of a roof over or
added insulation
Not any light weight building materials as
they can be a serious collapse hazard
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When the officer decides ventilation is needed,
they must consider the precaution necessary
to control the fire and assure the safety of
teams performing the task
The team must wear full PPE, including SCBA
and have a charge hose line available
Before, during , and following the operation it
is important to consider the possibility of fire
spreading through out a building and the
danger of exposure fires
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All PPE
Charged Hose Line
Forcible Entry
Tools
Chain Saw
Rotary Saw
Ladders
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Proper Ventilation simplifies and expedites
rescue by removing smoke and gases that
endanger trapped or unconscious occupants
Replacement of heat, smoke, and gases with
cooler, fresh air helps victims breathe better
This will also make condition safer for
firefighters and improve visibility so that we
may more easily locate the victims
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Vent team and fire attack must coordinate
closely
When the hole is cut, a chimney effect is created
in the structure
If this hole is cut directly over a fire, it tends to
localize the fire – If it is made on the other side
of the structure, it may well contribute to the
spread of the fire into unburned areas
Good ventilation will lessen the chances of
steam burns to firefighters and increase
visibility
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Property conservation will occur through
good ventilation because the attack team
will be able to find and extinguish the fire
quicker
It will allow the water fog, smoke, heat, and
gases to escape into the environment rather
than remain in the structure
All of this will allow better salvage
operations while the extinguishment is in
process
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Convection will cause the heat, smoke, and
gases to travel up to the highest point until they
are trapped by a roof or ceiling
As they accumulate, they bank down and spread
laterally to involve other areas
This process is called Mushrooming
Ventilation will reduce this effect
Fire must be put out quickly though or the extra
air coming in will allow the fire to expand
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Rollover is sudden ignition superheated
unburned gases across the ceiling space
Unburned gases gather across the ceiling
and when fresh air is supplied the ignite
Proper ventilation on the side of the fire
opposite the firefighters will reduce
chances of a rollover
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Flashover is the transition between growth and
fully developed fires
As original seat of the fire burns, everything
else in a room is heated to its ignition
temperature
Once reached, the entire room can burst into
flames simultaneously with severe
consequences to anyone in the room at this
time
Ventilation can relieve this as it lets the heat
escape before ignition temperatures are
reached
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High heat is available in a structure, but
oxygen levels are too low to support
combustion
A very dangerous condition exists because
the sudden admission of oxygen can cause a
sudden ignition called a backdraft
To prevent this, we need to provide vertical
ventilation to release trapped heat and
flammable products of combustion
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We need to be aware of this potential and proceed
cautiously if conditions are ripe for backdraft
Signs of potential backdraft include:
Smoke stained windows
Smoke puffing from the building {breathing}
Pressurized smoke from cracks in the building
Very little flame visible from the exterior
Black smoke becoming dense gray yellow
Confinement and excessive heat
IF ANY are seen, wait on vertical ventilation to be
completed before you try to enter the building
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We must understand our overall plan of
attack before we direct or order ventilation
to be started
We must make a series of decisions that
pertain to ventilation needs
These decisions should fall into the
following order
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This must be based on the
amount of heat, smoke,
and gas conditions within
the structure, structural
conditions, and the life
hazards
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This involves knowing
construction features of the
building, contents, exposures,
wind direction, extent of the
fire, location of the fire,
location of top or vertical
openings, and location of cross
or horizontal openings
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Horizontal?
Natural or Mechanical?
Vertical?
Natural or Mechanical?
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Must use all information available to you to
answer this question
Will need input from the people in the structure
and those going to the roof
To answer the questions, we have to evaluate
several pieces of information and take into
account many factors which are covered in the
next several slides
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The danger to human life is our utmost concern
Our first consideration is the safety of
firefighters and occupants
Proper ventilation will be needed in conjunction
with rescue operations
Dependant on the fire, ventilation may need to
happen before rescue operations, or if
conditions warrant, fire attack may need to
come first – in some cases, both will have to be
done at the same time
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There are also hazards to us as firefighters
The type of building, whether natural
openings are adequate, the need to cut
through roofs, walls, or floors of varying
types, all make the decision process more
difficult
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Some of the expected hazards due to an
accumulation of smoke and gases can be:
Obscurity caused by dense smoke
Presence of poisonous gases
Lack of oxygen
Presence of flammable gases
Backdraft
Flashover
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We can make some ventilation and tactical
decisions as we arrive at the scene based
on what visible smoke conditions we have
The density of the smoke is in direct ratio
to the amount of suspended particles
The conditions vary according to how
burning has progressed
A developing fire and a decaying fire are
two totally different fires and must be
treated as such
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An early stage fire will usually give off
smoke that is of not much density
If large quantities of carbon particles are
present, the smoke may become denser
As the building becomes more involved with
fire, the smoke will become denser
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Building type and design are the initial factors
to consider in determining whether to use
horizontal or vertical ventilation
Some other factors to consider:
Number and size of wall openings
Number of stories, staircases, shafts, ducts,
and roof openings
Availability and involvement of exterior fire
escapes and exposures
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Get in good with the building department so
they can let you know when buildings are
altered or subdivided
Building permits can reveal information about
the heating, ventilating, and HVAC systems
and avenues of escape for smoke, heat, and
fire gases
Adjoining buildings and how they are
attached has a bearing on ventilation
Pre plans can provide valuable information
and familiarity with the buildings in your
area
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Basement fires are among the most challenging
a firefighter will face
We basically have to descend through the
chimney to get to the fire
Access can be by interior or exterior stairs,
exterior windows, or hoist ways
Outside entrances may be blocked or secured
by iron gratings, steel shutters, wooden doors,
or combinations of these for protection from
weather and burglars
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Many buildings have windowless wall areas
While they may not be a desirable means of
escape, they are important considerations for
ventilation
Windowless buildings create and adverse effect
on firefighting and ventilation operations
Ventilation in windowless buildings may be
delayed for a long time, allowing the fire to
gain headway or to create backdraft conditions
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Problems in ventilating these building vary
depending on the size, occupancy,
configurations, and type of material from which
the building is constructed
They usually require mechanical ventilation for
the removal of smoke
The HVAC system can sometimes clear the
smoke by itself
The drawback to this is that it can also spread
the fire and it requires electricity to work
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Depending on time from ignition until
firefighters arrive, the fire may have traveled
some distance
We must consider the location and extent of the
fire when deciding on ventilation
Ventilation before fire location is know may
spread the fire into unburned areas
Severity and extent of the fire usually depend on
the type of fuel and amount of time it has been
burning, installed early warning and fire
protection devices, and degree of confinement
of the fire
Phase of the fire is a primary consideration
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Some means of vertical fire extension:
Through stairwells, elevators, and shafts by
direct flame contact or by convected air
currents
Through partitions and walls and upward
between the walls by flame contact and
convected air currents
Through windows or other outside openings
where flame extends to other exterior
openings and enters upper floors {lapping}
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Some means of vertical fire extension:
Through ceilings and floors by conduction or
heat through beams, pipes, or other objects
that extend from floor to floor
Through floor and ceiling openings where
sparks and burning material fall through to
lower floors
By the collapse of floors and roofs
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The ideal situation is one in which we have
prior knowledge of the building and its
contents
There is no exact rule except to open the roof
“as directly over the fire as possible”
Some of the may factors that will have a
bearing on where to ventilate include:
Availability of natural openings such as
skylights, ventilator shafts, monitors, and
hatches
Location of fire and direction in which the IC
wants it to be drawn
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Some of the many factors that will have a
bearing on where to ventilate include:
Type of building construction
Wind direction
Extent of progress of the fire and the condition
of the building and its contents
Bubbles or melting of roof tar
Indications of lessening structural integrity of
the roof
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Some of the many factors that will have a
bearing on where to ventilate include:
Effect that ventilation will have on the fire
Effect that ventilation will have on exposures
Attack crew’s state of readiness
Ability to protect exposures prior to actually
opening the building
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Before ventilating, adequate personnel and fire
control equipment must be ready because the
fire may increase in intensity once the building
is opened
Resources for the involved building and
exposures need to be in place
Try to attack the seat of the fire {if safe}
immediately after ventilation
Entrance should be made as close to the fire as
possible, with charged hoses in place in case of
flare up and at critical points of exposure
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Means opening the roof or existing roof
openings for the purpose of allowing heated
gases and smoke to escape to the
atmosphere
In order to properly ventilate, we must
understand the basic types and designs of
roofs
Study local roof types and the manner of
construction to develop effective vertical
ventilation policies and procedures
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We should be concerned with 3
prevalent types of roof shapes: Flat,
Pitched, and Arched
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Buildings may be constructed with a
combination of roof designs
Some of the more common styles are
the: flat, gable, gambrel, shed, hip,
mansard, dome, lantern, and butterfly
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We can undertake vertical ventilation after we
have considered the following:
Type of building involved
Location, duration, and extent of the fire
Observed safety precautions
Identified escape routes
Selected the place to ventilate
Moved personnel and tools to the roof
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Roof team should be in constant communication
with the IC
Responsibilities of the Roof Team Leader:
Ensure that only the required openings are made
Direct efforts to minimize secondary damage
Coordinating the crew’s efforts with those of the
firefighters inside the building
Ensuring the safety of all personnel who are
assisting in the opening of the building
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Observe the wind direction with relation to
exposures
Work with the wind at your back or side to
provide protection while cutting the roof
opening
Note the existence of obstructions or excess
weight on the roof. These may make
operations more difficult or reduce the
amount of time before a roof flails.
Provide a secondary means of escape for
crews on the roof
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Exercise care in making the opening so that
main structural supports are not cut
Guard the opening to prevent personnel from
falling into the building
Evacuate the roof promptly when ventilation
work is complete
Use lifelines, roof ladders, or other means to
protect personnel from sliding and falling off
the roof
Make sure that a roof ladder is firmly secured
over the peak of the roof before using it
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Exercise caution in working around electric
wires and guy wires
Ensure that all personnel on the roof are
wearing full personal protective equipment
including SCBA
Keep other firefighters out of the range of
those handling axes and operating power saws
Caution axe users to beware of overhead
obstructions within the range of their axe
Make sure that the angle of the cut is not
toward the body
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Start power tools on the ground to ensure
operation; however, it is important that the
tools be shut off before hoisting or carrying
them to the roof
Extend ladders at least five rungs above the
roof line and secure the ladder. When using
elevating platforms, the floor of the platform
should be even with or slightly above roof level
Check the roof for structural integrity before
stepping on it; do not jump onto a roof without
checking it first
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Use pre plans and surveys to identify
buildings that have roofs supported by
lightweight or wooden trusses. Realize that
these roofs may fail early into a fire and are
extremely dangerous to be on or under
Work in groups of at least two, but not
more people than absolutely necessary to
get the job done
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Beware of the following warning signs of an
unsafe roof condition:
Melting Asphalt
Spongy Roof {a normally solid roof that springs
back when walked upon}
Smoke coming from the roof
Fire coming from the roof {if it has already
vented itself, we probably do not need to}
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May be found on various types of roofs
Almost all of them will be locked or secured in
some manner
Scuttle hatches are normally square and large
enough to permit a person to climb onto the
roof
They may be metal or wood and generally do
not provide an adequate opening for
ventilation
Skylights with ordinary glass can be easily
shatter, but if they contain wired glass,
Plexiglas, or Lexan, they will difficult to shatter
and you will do better to attack the framing
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The sides of a monitor may contain glass or
louvers made of wood or metal
Usually have hinged sides that are easily forced
at the top
If you cannot remover the top, open at least
two sides to create the required draft
Force open stairway doors like you would any
door of the same type
It is usually quicker to use one of these
openings than to cut a hole in the roof
Drawbacks are their placement and size
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Pre planning is the best way to learn about the
types and construction of roofs in your area
When cutting a roof, one large opening is
better than many small ones
Also, try to cut a square or rectangular hole in
order to make repairs to the building easier
Power saws are the best equipment for
opening roofs, making the work a lot quicker
Safety of the operator and crew are paramount
Pre plans can clue us in as to what equipment
we will need to open a specific roof
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Several types of cuts may be used on a roof:
Kerf Cut: Basically you just put the saw blade
through the roof to look for fire and determine
direction of spread
Inspection Opening: Make a triangular hole by
placing the blade into the roof three times – This
can be done when you first get on the roof and
as you move away from your point of egress –
You are checking for fire under you
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Several types of cuts may be used on a roof:
Louvered Cuts: May be used when cutting
through plywood
The cuts are made in between the rafters rather
than beside them.
The panels are then hinged on the rafters
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Most commonly found on commercial, industrial,
and apartment buildings, {and older homes in
Florida}
May or may not have a slight slope for drainage
Frequently pierced by chimneys, vent pipes,
shafts, scuttles, and skylights.
May be surrounded and/or divided by parapets,
and it may support water tanks, air-conditioning
equipment, antennas, and other obstructions to
ventilation operations
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Structurally, they are generally similar to a
floor that consists of wooden, concrete, or
metal joists covered with sheathing
The sheathing is covered with a layer of
waterproofing material and an insulating
material
Sometimes, these roofs can be poured
reinforced concrete or lightweight concrete,
pre-cast gypsum, or concrete slabs se in
metal joists
Pre plans, again, will tell us what type of roof
it is and what we need to open it
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These are elevated in the center and form a
pitch to the edges
They involve rafters or trusses that run from
the ridge to a wall plate on top of the outer
wall at the eaves level
The rafters or trusses can be made out of
various materials
Sheathing is applied over these, then roofing
paper, then shingles or other roof covering
Shingles may be wood, metal, composition,
asbestos, slate, or tile
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On barns, churches, supermarkets, or
industrial buildings, you may have roll felt over
the sheathing
This can be mopped on with asphalt roofing
tar
Instead of wood sheathing, you may find
gypsum slabs approximately 2” thick
The incline on these roofs can be very gradual
or very steep
Personnel safety is still the main prerogative
when venting, take extra precautions as
needed
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Some of these may be easier to get into:
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If the roofing material is slate or tile, you may
be able to open it with a sledgehammer
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Smash the slate or tile, and also the thin lath
strips or 1x4’s that they are held up by
Tin roofs can be sliced open and peeled back
with tin snips or a large device similar to a can
opener
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One form of this is constructed with
bowstring trusses for supporting members
They conceal large un-vented spaces which
create dangerous ventilation problems and
contribute to the spread of fire and early
failure of the roof
WARNING:
Many firefighters have lost their lives while a
trussed roof has failed. A good rule to follow
is that when a significant amount of fire
exists in the truss area of a roof structure,
firefighters should not be on or under a truss
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Trussless arched roofs are made of
relatively short timers of uniform length
This network forms an arch of mutually
braced and stiffened timbers
Because it is not a truss, a hole of
considerable size may be cut or burned
through the sheathing and roofing without
causing collapse of the roof structure
Vent them the same as you would other
roofs, with safety being an issue because
you will not be able to use a roof ladder –
Use a ladder truck! ~Mutual Aid~
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Precast roof slabs are available in many
shapes, sizes, and designs
Can be trucked in or built on site
These are very difficult to break through and
opening them should be avoided whenever
possible
Us natural roof openings and horizontal
openings
Popular lightweight materials made of gypsum
plaster and Portland cement mixed with
aggregates, such as perlite, vermiculite, or
sand provided a lightweight floor and roof
assembly often referred to as lightweight
concrete
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Lightweight precast planks and slabs are
reinforced with steel mesh or rods
The roof is usually finished with roofing felt
and a mopping or hot tar to seal it
These roof decks can be poured over
permanent form boards, steel roof decking,
paper-backed mesh, or metal rib lath
They are relatively easy to ventilate with a
hammer head pick, power saw with concrete
blade, jackhammer, or other penetrating tool
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Can be made from several different kinds of
metal and constructed in many styles
Light gauge steel roof decks can either be
supported on steel frameworks or they can
span wider spaces
Corrugated roofing sheets can be made from
light gauge cold formed steel, galvanized
sheet metal, or aluminum
Light gauge cold formed steel is used
primarily for roofs of industrial buildings
These are seldom covered and can be pried
from their supports
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Metal cutting tools or power saws with
metal cutting blades must be used
Industrial building usually have adequate
natural roof openings, skylights, or hatches
Older buildings may have roofs that are
made of large, fairly thin sheets of tin over
lath strips
They can be opened by cutting with a power
saw, axe, or large sheet metal cutter
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This is used a little differently than
standard ventilation techniques
Trench ventilation is used to stop the
spread of fire in a long, narrow structure
It is performed by cutting a large hole
{trench} that is at least 4 feet wide and
extends from one exterior wall to the
opposite one
Usually cut well ahead of the advancing
fire for the purpose of setting up a
defensive line where the fire’s progress
will be halted
Rest of the building is written off
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Without built in vents, the heat and smoke
from these fires will quickly spread up into
the building
Especially true of balloon frame construction
In balloon frame, fire may go from the
basement to the attic without showing
anywhere in between
Ventilation of a basement can be
accomplished in several ways
If windows are present, horizontal
ventilation can be used
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If no windows are present, you will have to
use interior vertical ventilation with natural
paths from the basemen, such as stair wells
and hoist way shafts
Try to direct this smoke outside on the first
floor without spreading it to other portions
of the building
The last resort would be to cut a hole in the
floor near a first floor window or door to vent
the basement, and put a fan in the window /
door to draw the smoke out of the building
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Once vertical ventilation is done, the
convection of heated gases creates upward
currents that draw the fire and heat toward
the opening
Team inside will have better visibility and
less contaminates in the air to make their
attack easier
You can direct hose streams over the
opening to lessen sparks and flying embers
DO NOT direct the stream downward
through a ventilation opening as this will
upset the orderly movement of gases
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If the gas movement is upset, it can force super
heated air and gases back down on the interior
crews causing serious injury or death
It can also contribute to the spread of fire
Project your ventilation streams just above the
opening and slightly above the horizontal plane
of the roof
They will help cool the thermal column and
extinguish sparks and maybe speed the rate of
ventilation
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Factors that can destroy vertical ventilation:
Improper use of forced ventilation
Excess breakage of glass
Fire streams directed into ventilation holes
Breakage of skylights
Explosions
Burn through of the roof, a floor, or a wall
Additional opening between the attack team and
the upper opening
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WARNING:
Never operate any type of fire stream through
a ventilation hole during offensive operations.
This stops the ventilation process and places
interior crews in serious danger
Vertical ventilation is not the solution to all
ventilation problems because it is sometimes
impractical or impossible
You must be able to use all types of ventilation
to be effective
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Venting of heat, smoke, and gases through
wall openings such as windows or doors
Structures that lend themselves to
horizontal ventilation include:
Residential building where fire has not
involved the attic
Involved floors of multistoried buildings
below the top floor, or the top floor if attic
is uninvolved
Buildings with large, unsupported spaces
under the roof where the structure has been
weakened by the effects of burning
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Different procedures are used to
horizontally ventilate a room , floor,
cockloft, attic, or basement
Procedures will be influenced by the
location and extent of the fire
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Some of the ways of horizontal extension
are:
◦ Through wall openings by direct flame contact
or by convected air
◦ Through corridors, halls, or passage ways by
convected air, 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 conduction across pipes,
beams or other objects that extend through
them
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This is always an issue in deciding the
horizontal ventilation procedure
Wind is an important factor
Direction may be designated as windward
{side wind is hitting} or leeward {opposite
or downwind side}
If there is no wind, natural horizontal
ventilation is less effective because there
is not force to remove the smoke
In other cases, exposures on the leeward
side can be in severe danger
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Routing of smoke and heat becomes an issue
in horizontal ventilation
We should be aware of internal and external
exposures
The routes we use to move the smoke and
heated gases can be the same corridors
occupants and firefighters will be using
First consideration of horizontal ventilation
needs to be the escape routes of the
occupants and rescue routes of the firefighters
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Horizontal ventilation is not accomplished at
the highest point in a building, therefore there
is the danger that when the rising heated gases
are released, they will ignite highest portions of
the building
This could be the eaves of this building or an
adjacent building, or they may enter a window
above the ventilation point
Building should not be opened {unless
immediate rescue is needed} until charge lines
are in place to attack @ the point where fire
might be expected to spread
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Opening a door or breaking a window on the
windward side before the leeward side may
pressurize the building and upset the thermal
layering
Opening doors and windows between the entry
team and the established ventilation exit reduces
the intake of fresh air from the opening behind
the entry team
95
96
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This is accomplished mechanically {fans} or
hydraulically {fog streams}
The principal is to move large quantities of
smoke and air
Forced ventilation equipment is difficult to
classify by a a particular type
Fans can be powered by electric motors,
gasoline engines, or water pressure from
hose lines
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Some of the reasons for employing forced
ventilation include the following
Ensures more positive control of the fire
Supplement natural ventilation
Speeds the removal of contaminants,
facilitating a more rapid rescue under safer
conditions
Reduces Smoke damage
Promotes better public relations
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Misapplied or improperly controlled forced
ventilation can cause a great deal of harm
It requires supervision because of the
mechanical force behind it
Some disadvantages are:
Introduces air in such great volumes that it can
cause the fire to intensify and spread
Depends upon a power source
Requires special equipment
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Oldest of mechanical forced ventilation
techniques: uses fans to develop artificial
circulation and pull smoke out of a structure
Fan is placed in a window, door, or roof vent
hole and they pull the smoke, heat, and gases
from inside the building and eject them to the
exterior
The fan should be set up to exhaust in the same
direction as the wind flow
This will help the wind, speed up the process
and supply fresh air to replace what is being
removed
10
0
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If natural wind is too light to be effective, you
can place fans blowing in on one side and
exhausting on the other side
Recirculating air around the fan can be an issue
This can cause a churning effect that reduces
efficiency
To prevent this, cover the area around the fan
with salvage covers or other materials
Select your desired path and keep it in as
straight a line as possible
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1
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Every corner will cause turbulence and
decrease efficiency
Do not open doors or windows near the
exhaust fan unless it definitely increases
circulation
Remove items such as curtains, drapes,
blinds or anything that can reduce airflow
The fans should have explosion proof
motors and power cords / connectors
They should be turned off with they are
moved
When starting, clear the area of people &
loose items
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2
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Ventilation technique that uses the principle
of creating pressure differentials
A higher pressure is created in the build than
that outside by using high volume fans
Due to the high pressure inside the building
the smoke will seek and outlet to a lower
pressure zone through openings controlled
by the firefighters
The location where the fan blows in, usually
an exterior doorway, is called the point of
entry
Place the fan several feet outside the door so
that a cone of air covers the entire door
opening
10
3
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Smoke is ejected from exhaust openings
the same size or smaller than the entry
opening
Do not open other openings while positive
pressure is in use, except the point of
exhaust
We can now close doors and windows,
pressurizing one room or at a time, in order
to speed up ventilation
Additional fans can be placed @ the point of
entry to increase the CFM flow and thus the
interior pressure
10
4
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If you do not systematically control the
exhaust points, the ventilation will work,
but it will take a lot longer
When using on multiple floor buildings,
the point entry should be at the lowest
point.
Smoke can then be systematically removed
starting at the floor most charged with
smoke {straight out of the book}
It is best to start exhausting at the lowest
point and work your way up {experience –
if you start in the middle, you will have to
do that floor again as smoke from the
lower floors will drift up there}
10
5
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PPV requires good fire ground discipline,
coordination, and tactics
The main probable is coordinating the opening
and closing of doors is stairwells
People may stand with doors to the stairwell or
their door open and redirect the PPV away from
where you want it
Place a person in charge of the pressurizing
process, use radios to make sure it is working
properly
10
6
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Take advantage of existing wind conditions
Make certain that the cone of air from the
fan covers the entire entry opening
Reduce the size of the area being
pressurized to speed up the process by
systematically opening and closing doors or
by increasing the number of fans
Keep the size of the exit opening in
proportion to the entry opening
10
7
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Firefighters can set up PPV without entering
the smoke filled environment
PPV is equally effective with horizontal or
vertical ventilation because it merely
supplements natural ventilation currents
More efficient removal of smoke and heat from
a structure or vessel is allowed
The velocity of air currents in a building is
minimal and has little, if any, effects that
disturb the building contents or smoldering
debris. Yet the total exchange of air within the
building is faster than using NPV
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8
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Fan powered by internal combustion engines
operate more efficiently in clean, oxygen
rich atmospheres
The placement of fans does not interfere
with ingress or egress
The cleaning and maintenance of fans used
for positive pressure ventilation is greatly
reduced compared to that of those used in
negative pressure ventilation
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This is applicable to all types of structures
or vessels and is particularly effective at
removing smoke from large, high ceiling
areas where NPV is ineffective
Heat and smoke may be directed away
from unburned areas or paths of exit
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An intact structure is required
Interior carbon monoxide levels may be
increased during use
Hidden fires may {will} be extended
11
1
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May be used where other types of forced
ventilation are not being used
It is performed by hose teams inside the fire
building
It is used to clear the room or building of smoke,
heat, steam, and gases following the initial
knockdown of the fire
It takes advantage of the air that is drawn into a
fog stream to help pus the products of
combustion out of the structure
11
2
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To perform, set a fog stream to wide pattern
that will cover 85 to 90 percent of the window
or door opening from which the smoke will be
pushed out
Nozzle tip should be at least 2 feet from the
opening
The larger the opening, the faster the
ventilation
There are some drawbacks to using fog
streams to perform forced ventilation
11
3
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There may be an increase in the amount of
water damage within the structure
There will be a drain on the available water
supply. This is particularly crucial in rural
firefighting operations where water shuttles
are being used
In climates subject to freezing temperatures,
there will be an increase in the problem of ice
in the are surrounding the building
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4
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The firefighters operating nozzle must
remain in the heated, contaminated space
during the operations
The operation may have to be interrupted
when the nozzle team has to leave the area
for some reason {SCBA, Rehab, Etc.}
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5
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Most modern building have HVAC systems
These systems can contribute to fire and
smoke spread throughout a building
Pre plans should include information on
the systems design and use along with
diagrams of the duct system and fire
protection within
We should know the location and operation
of the controls that will manually shut
down the system when so desired
System may draw heat and smoke in, so
always check the duct work and areas
around it for extension
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Remember, this system will need to be
ventilated before it is restarted
In large buildings or where large numbers of
people are present, the building may have a
smoke control system
They involve the mechanical systems, doors,
partitions, windows, shafts, ducts, fan dampers,
wire controls, and pipes
We should know about these in our pre plans
We should not try to operate them due to their
differences and complexity. Call the occupants.
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Typical high rise occupancies are hospitals,
hotels, apartments, and office buildings
All these equal a lot of people in danger in a fire
Fire and smoke may spread rapidly through pipe
shafts, stairways, elevator shafts, air-handling
systems, and other vertical openings
These openings cause a stack effect {natural,
vertical heat and smoke movement throughout a
building} creating an upward draft and
interfering with evacuation and ventilation
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Layering of smoke and gases on floors below
the top floor of un-vented multi-story
buildings is possible
These gases travel up until their temperature
is reduced to the same as the surrounding air
When this happens, the smoke and gases will
mushroom on this floor or in this area
The layering of smoke at an area of
temperature equalization is called
stratification
Pre plans should include tactics and
strategies to deal with this problem in tall
buildings
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9
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High rise ventilation must be carefully
coordinated to ensure the effective use of
personnel, equipment, and extinguishing
agents
Personnel demand will be approximately 4
to 6 times what it is for a normal house
fire
Consider using horizontal ventilation @
stratification level
SCBA and extra bottles will be in great
demand
Communication and coordination among
teams will become more difficult due to
the number of people on the scene
12
0
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Top ventilation must be considered during pre
planning
Often, in these buildings, only one stairwell
goes to the roof
We must know which one so we can use this as
a chimney to ventilate the building
Block this door open or take it off its hinges
before you begin opening the interior stairwell
doors
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1
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Failure to open / secure this door can
result in the stairwell becoming filled with
superheated fire gases and smoke
Elevator shafts may also penetrate the
roof line and may be used for ventilation
Using stairwells or elevator shafts for
evacuations and ventilation
simultaneously is potentially lifethreatening
12
2
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Failure to open / secure this door can
result in the stairwell becoming filled with
superheated fire gases and smoke
Elevator shafts may also penetrate the
roof line and may be used for ventilation
Using stairwells or elevator shafts for
evacuations and ventilation
simultaneously is potentially lifethreatening
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3
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8-1.3 Demonstrate opening various
types of windows from inside and
outside, with and without fire department
tools.
8-1.4 Demonstrate breaking windows or
door glass, and removing obstructions.
8-1.5 Demonstrate ventilation of a floor
or roof using an axe.
8-1.6 Demonstrate ventilation using a
water fog stream.
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4
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8-2.1 Demonstrate the use of different type
of power saws and jack hammers.
8-2. Demonstrate the techniques for
ventilating different types of roofs.
8-2.4 Demonstrate the removal of existing
roof opening. I.e.: skylights, scuttle covers,
and other roof openings.
8-2.5 Demonstrate the different types of
equipment used for forced ventilation.
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5
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8-3.1 Demonstrate natural and mechanical
methods for horizontal ventilation.
8-3.2 Demonstrate natural and mechanical
methods for vertical ventilation.
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6
THE END
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