CVFD Training – Ventilation
Practices
SFFMA Training Objectives:
8-01.05 – 8-01.08
Vertical Ventilation
• Opening roof/existing roof openings for
allowing heated gases, smoke to escape
• Firefighters must understand basic types,
designs of roofs
(Continued)
Firefighter I
11–2
Vertical Ventilation
• Firefighters must know how roofs in the
response areas are constructed
(Continued)
Firefighter I
11–3
Vertical Ventilation — Preincident
Inspections
• Identify
– New construction projects
– Existing construction
– Use of lightweight building materials
– Information that can alert firefighters
Firefighter I
11–4
Likelihood of Roof Collapse During
Vertical Ventilation
• Based on
– Volume of fire
– How long fire has been burning
– Type of construction
– Level of protection
– Load on roof
Firefighter I
11–5
Responsibilities During Vertical
Ventilation — Officer in Charge
•
•
•
•
Determine it can be done safely, effectively
Consider age, type of construction
Consider location, duration, extent of fire
Observe safety precautions
(Continued)
Firefighter I
11–6
Responsibilities During Vertical
Ventilation — Officer in Charge
• Identify escape routes
• Select place to ventilate
• Move personnel, tools to roof
Firefighter I
11–7
Responsibilities During Vertical
Ventilation — Leader on Roof
•
•
•
•
Ensure roof safe to operate on
Ensure only required openings made
Direct efforts to minimize secondary damage
Coordinate crew’s efforts with firefighters
inside building
(Continued)
Firefighter I
11–8
Responsibilities During Vertical
Ventilation — Leader on Roof
• Ensure safety of all personnel
• Ensure team leaves roof as soon as
assignment completed
Firefighter I
11–9
Safety Precautions During Vertical
Ventilation
• Check wind direction with relation to
exposures
• Work with wind at back/side to provide
protection while cutting
• Note existence of roof obstructions/
excessive weight on roof
(Continued)
Firefighter I
11–10
Safety Precautions During Vertical
Ventilation
• Provide secondary means of escape for crews
(Continued)
Firefighter I
11–11
Safety Precautions During Vertical
Ventilation
• Ensure main structural components not cut
while creating opening
• Guard opening to prevent personnel falling
into it
• Evacuate roof promptly when ventilation
complete
(Continued)
Firefighter I
11–12
Safety Precautions During Vertical
Ventilation
• Use lifelines, roof ladders, other means to
prevent sliding/falling
• Make sure roof ladder (if used) firmly secured
over roof’s peak
• Exercise caution when working around
electric, guy wires
(Continued)
Firefighter I
11–13
Safety Precautions During Vertical
Ventilation
• Ensure all personnel on roof wear full PPE
including SCBA
• Keep other firefighters out of range of those
swinging axes, operating saws
• Caution axe users to be aware of overhead
obstructions
(Continued)
Firefighter I
11–14
Safety Precautions During Vertical
Ventilation
• Start power tools on ground to ensure
operation; shut off before hoisting/
carrying to roof
• Extend ladders 3-5 rungs above roof line,
secure ladder
• When operating from aerial ladder platforms,
floor of platform even with/
slightly above roof level
(Continued)
Firefighter I
11–15
Safety Precautions During Vertical
Ventilation
• Check roof for structural
integrity before stepping
on, continue sounding
throughout operation
(Continued)
Firefighter I
11–16
Safety Precautions During Vertical
Ventilation
• Always walk on bearing walls, strongest points
of roof structure
• Ensure ceilings punched through to enhance
ventilation
Firefighter I
11–17
Unsafe Roof — Warning Signs
•
•
•
•
Melting asphalt
Spongy Roof
Smoke coming from roof
Fire coming from roof
Firefighter I
11–18
DISCUSSION QUESTION
What should you do if you are assigned to
ventilate a roof and find warning signs
present?
Firefighter I
11–19
Roof Coverings
• Part of roof
exposed to weather
• Types
• Some susceptible to
ignition from sparks,
burning embers; others not
• Some have coating of insulating material
Firefighter I
11–20
Existing Roof Openings
• Sometimes used for vertical ventilation
• Rarely in best location/large enough
• Usually supplement cut holes
(Continued)
Firefighter I
11–21
Existing Roof Openings
•
•
•
•
•
Scuttle hatches
Skylights
Monitors
Ventilating shafts
Penthouse/bulkhead doors
Firefighter I
11–22
General Ventilation Considerations for
Roofs
• Square/rectangular opening
easier to cut, easier to repair
• One large opening better
than several small
Firefighter I
11–23
Flat Roofs
• Commonly found on
commercial,
industrial, apartment
buildings
• Common on many
single-family
residences
(Continued)
Firefighter I
11–24
Flat Roofs
• May/may not have slight slope for drainage
• Frequently penetrated by chimneys, vent
pipes, etc.
• May be surrounded and/or divided by
parapets
(Continued)
Firefighter I
11–25
Flat Roofs
• May support water tanks, HVAC
equipment, etc.
• Structural part
• Decking
• Construction materials determine
equipment necessary to ventilate
Firefighter I
11–26
Pitched Roofs
• Among most
common are those
elevated in center
along ridge with roof
deck sloping down to
eaves along roof
edges
(Continued)
Firefighter I
11–27
Pitched Roofs
• Shed roofs — Pitched along one edge with
deck sloping down to eaves at opposite edge
• Most involve rafters/trusses
• Have more pronounced downward slope than
flat; may be steep
(Continued)
Firefighter I
11–28
Pitched Roofs
• Procedures for opening similar to flat roofs;
precautions must be taken to prevent slipping
• Some types may require different opening
techniques
Firefighter I
11–29
Arched Roofs
• Can span large open areas unsupported by
pillars/posts
• One type uses bowstring trusses
(Continued)
Firefighter I
11–30
Arched Roofs
• Lamella or trussless
arched roofs
(Continued)
Firefighter I
11–31
Arched Roofs
• Procedures for cutting ventilation openings
same as flat/pitched except no ridge to hook
roof ladders; curvature of roof prevents roof
ladders from lying flat
Firefighter I
11–32
Precast Concrete Roofs
• Can be fabricated off-site
• Available in many shapes, sizes, designs
(Continued)
• Some use lightweight material
Firefighter I
11–33
Precast Concrete Roofs
• Lightweight usually finished with roofing felt
and mopping of hot tar
• Extremely difficult to break through
• Existing openings should be used for
ventilation on heavy roofs
Firefighter I
11–34
Poured-In Place Concrete Roofs
• Some lightweight concrete roof decks
poured in place over permanent form
boards, steel roof decking, paper-backed
(Continued)
mesh, or metal rib lath
Firefighter I
11–35
Poured-In Place Concrete Roofs
• Relatively easy to penetrate
• Some can be penetrated with hammer-head
pick or power saw with concrete blade
• Heavier roofs require jackhammer/
diamond-tipped chain saw
Firefighter I
11–36
Metal Roofs
• Made from several different kinds of metal;
constructed in many styles
(Continued)
Firefighter I
11–37
Metal Roofs
• Light-gauge steel roof decks can be supported
on steel frameworks/laid over existing roof
• Light-gauge cold-formed steel sheets used
primarily for industrial buildings
(Continued)
Firefighter I
11–38
Metal Roofs
• Except when covered with lightweight
concrete, seldom covered with roofing
material
• Metal cutting tools/power saws with metal
cutting blades must be used to open
(Continued)
Firefighter I
11–39
Metal Roofs
• Often penetrated by roof openings
• Older buildings may have roofs made of large
pieces of sheet metal laid over skip sheathing
Firefighter I
11–40
DISCUSSION QUESTION
What are some examples of occupancies in
your area? How would these occupancies
need to be addressed when ventilating the
building?
Firefighter I
11–41
Trench Ventilation (Strip Ventilation)
• Used to stop
spread of fire in
long, narrow
structure
(Continued)
Firefighter I
11–42
Trench Ventilation (Strip Ventilation)
• Performed by cutting large opening at least 4
feet (1.2 m) wide extending from one exterior
wall to opposite exterior wall
• Often, large ventilation opening is cut
between trench cut and fire
Firefighter I
11–43
Conventional Basement Ventilation
• In absence of built-in
vents from basement,
heat and smoke from
basement fires quickly
spread upward
(Continued)
Firefighter I
11–44
Conventional Basement Ventilation
• Can be accomplished
several ways
– Ground-level windows —
horizontal ventilation
– Windows unavailable —
interior vertical ventilation
Firefighter I
11–45
Factors Reducing Effectiveness of
Vertical Ventilation
•
•
•
•
Improper use of forced ventilation
Indiscriminant window breaking
Fire streams directed into ventilation openings
Breaking skylights
(Continued)
Firefighter I
11–46
Factors Reducing Effectiveness of
Vertical Ventilation
• Explosions
• Burn-through of roof, floor, wall
• Additional openings between attack team,
upper ceiling
Firefighter I
11–47
Negative-Pressure Ventilation (NPV)
• Oldest type of mechanical forced ventilation
techniques — Using fans to develop artificial
circulation/enhance natural ventilation
(Continued)
Firefighter I
11–48
Negative-Pressure Ventilation (NPV)
• Fans placed in windows, doors, roof vent
openings to exhaust smoke, heat, gases
(Continued)
Firefighter I
11–49
Negative-Pressure Ventilation (NPV)
• NPV operations
– Fan should be positioned to exhaust in same
direction as prevailing wind
– Technique uses wind to supply fresh air
– If prevailing wind too light, fans can be positioned
on windward side of structure to blow air into
building
(Continued)
Firefighter I
11–50
Negative-Pressure Ventilation (NPV)
• If open areas around smoke ejector not
properly sealed
– Air can recirculate into building
– Atmospheric pressure pushes air back through
spaces; smoke reenters room
– To prevent recirculation, cover area around fan
(Continued)
Firefighter I
11–51
Negative-Pressure Ventilation
(NPV)
• Flow of smoke, other gases to exit opening
should be kept straight as possible
(Continued)
Firefighter I
11–52
Negative-Pressure Ventilation
(NPV)
• Avoid opening windows near exhaust fan
because this can reduce efficiency
• Remove all obstacles to airflow
(Continued)
Firefighter I
11–53
Negative-Pressure Ventilation
(NPV)
• Do not allow intake side of fan to become
obstructed
• When ventilating potentially flammable
atmospheres, only exhaust fans with
intrinsically safe motors, power cable
connections should be used
(Continued)
Firefighter I
11–54
Negative-Pressure Ventilation
(NPV)
• Exhaust fans should be turned off when
moved; carry by handles
• Before starting exhaust fans, be sure no one
near blades; other materials not in position to
be drawn into fan
• Discharge stream of air should be avoided
(Continued)
Firefighter I
11–55
Positive-Pressure Ventilation (PPV)
• Forced ventilation
technique that uses highvolume fan to create
slightly higher pressure
inside than that outside
(Continued)
Firefighter I
11–56
Positive-Pressure Ventilation (PPV)
• As long as pressure
higher inside building,
smoke within building
forced through
ventilation exit
opening
(Continued)
Firefighter I
11–57
Positive-Pressure Ventilation (PPV)
• Location where PPV set up is entry point
– Once location selected, create exit opening
opposite
– Size of exit opening varies with size of entry
opening, capacity of blower
– Exit opening may be window/doorway
(Continued)
Firefighter I
11–58
Positive-Pressure Ventilation (PPV)
• Once exit opening created
– Blower placed 4-10 feet (1.2-3 m) outside open
entry point
– Smoke then expelled from exit opening
– To maintain positive pressure inside, important
that no other exterior doors/
windows are opened during operation
(Continued)
Firefighter I
11–59
Positive-Pressure Ventilation (PPV)
• By selectively opening, closing interior doors
and exterior windows, it is possible to
pressurize one room/area at a time
(Continued)
Firefighter I
11–60
Positive-Pressure Ventilation (PPV)
• Several considerations for using PPV to
ventilate multistory building
• Requires good fireground discipline,
coordination, tactics
(Continued)
Firefighter I
11–61
Positive-Pressure Ventilation (PPV)
• Main problem in aboveground operations —
Coordinating opening, closing of doors in
stairwell
• To control openings/pressure leaks, put one
person in charge of pressurizing process
(Continued)
Firefighter I
11–62
Positive-Pressure Ventilation (PPV)
• To ensure effective PPV operation
– Take advantage of existing wind
– Make certain cone of air from blower covers
entire entry opening
– Reduce size of area being pressurized to speed up
process by selectively opening, closing interior
doors
(Continued)
Firefighter I
11–63
Positive-Pressure Ventilation (PPV)
• To ensure effective PPV operation
– Keep size of exit opening in proportion to entry
opening
– Avoid creating horizontal openings by breaking
glass/removing doors
Firefighter I
11–64
Advantages of PPV Compared to
NPV
• Firefighters can set up PPV without entering
smoke-filled environment
• PPV usually effective with horizontal or
vertical ventilation
• Removal of smoke, heat more efficient with
PPV
(Continued)
Firefighter I
11–65
Advantages of PPV Compared to
NPV
• Velocity of air currents within building
minimal and minimally disturb building
contents/debris
• Fans powered by internal combustion engines
operate more efficiently in clean, oxygen-rich
atmospheres
(Continued)
Firefighter I
11–66
Advantages of PPV Compared to
NPV
• Placement of fans does not interfere with
ingress/egress
• Cleaning, maintenance of fans for PPV less
than those for NPV
• PPV effective in all types of structures
(Continued)
Firefighter I
11–67
Advantages of PPV Compared to
NPV
• Heat, smoke may be directed away from
unburned areas/paths of exit with PPV
• Exposed buildings can be pressurized by PPV
to reduce fire spread
Firefighter I
11–68
Disadvantages of PPV
• Intact structure required
• Interior carbon monoxide levels may be
increased if exhaust from fans allowed to
enter
• Hidden fires may be accelerated, spread
throughout building
Firefighter I
11–69
DISCUSSION QUESTION
In what types of fires do you think PPV would
be more effective? In what types of fires will
NPV work better?
Firefighter I
11–70
Hydraulic Ventilation
• May be used in situations where other
types of forced ventilation unavailable
• Used to clear room or building of smoke,
heat, steam, gases after fire controlled
(Continued)
Firefighter I
11–71
Hydraulic Ventilation
• Uses air movement created by fog stream
to help draw products of combustion out of
structure
Firefighter I
11–72
Performing Hydraulic Ventilation
• Fog stream set on wide fog pattern that covers
85-90 percent of window/door opening from
which smoke will be pushed out
• Nozzle tip should be at least 2 feet (0.6 m)
back from opening
• Larger the opening, faster the process
(Continued)
Firefighter I
11–73
Performing Hydraulic Ventilation
Firefighter I
11–74
Disadvantages to Hydraulic
Ventilation
•
•
•
•
May increase amount of water damage
Drain on available water supply
If freezing, increase in ice on ground
Firefighters operating nozzle must remain in
heated, contaminated area
• Operation may be interrupted when nozzle
team leaves to replenish air
Firefighter I
11–75
Building Systems
• Many modern buildings have built-in HVAC
systems
• Systems can significantly contribute to spread
of smoke, fire throughout structure
Firefighter I
11–76
Building System Operations
• Usually controlled from panel in maintenance
and operations center in the building
• Wherever located, often diagram of duct
system and information on smoke detection,
fire suppression systems built into HVAC
ductwork
(Continued)
Firefighter I
11–77
DISCUSSION QUESTION
Who should operate building systems to assist
in ventilation?
Firefighter I
11–78
Building System Operations
• Systems designed to shut HVAC system down
automatically when smoke/fire detected in
ducts
Firefighter I
11–79
Fire Personnel
• Should be familiar with location, operation of
controls allowing them to shut down HVAC
system
• May need to shut HVAC system down during
fire; clearing system of smoke, restoring to
operation responsibility of building engineer
or maintenance superintendent
(Continued)
Firefighter I
11–80
Fire Personnel
• Should check combustibles adjacent to
ductwork for fire extension due to conduction
Firefighter I
11–81
Smoke Control Systems
• Many other buildings equipped with built-in
smoke control systems
• Designed to confine fire to as small an area as
possible
• Achieve confinement by automatic closure of
doors, partitions, windows, fire dampers
(Continued)
Firefighter I
11–82
Smoke Control Systems
• Usually have system diagram in same location
as control panel; panel should indicate where
alarm originated, which automatic closers
activated
Firefighter I
11–83