Chapter 16 Ventilation Flashcards
What is Thermal layering
Thermal layering is the layering of heated gases according to temperature – the
hottest gases tend to be on the top layer
The firefighter must consider what four factors pertaining to the smoke:
VOLUME
VELOCITY
DENSITY
COLOR
“Volume sets the stage for Velocity”
what Various products produce different colors of
smoke. Take in mind though – it may not
always indicate the true combustible burning.
Wood & paper products - Gray Smoke
Hydrocarbons, plastic - Black Smoke
Nitrogen Oxides - Brown/Copper Smoke
Steam – White
What is black fire and what is your only choice pertaining to it
is the term we give to high
volume, high velocity, and extremely dense,
black smoke. It is a sure indicator of an impending flashover. Treat black fire just as
actual flames.
Your only choice is to “aggressively cool and back out”
What are the Two types of exposures
Internal
● The routes by which the heat and smoke travel to the exit may be the same
corridor that the occupants and firefighters may be using for evacuation.
Higher portions of a building could ignite with the use of horizontal
ventilation. The path of the fire gases, as they exit the structure, carries the fire
to other locations of the building.
External
● At the point of exit, the products of combustion may cause other structures
adjacent or parts of the same structure above the exhaust opening to become
heated to their ignition points.
What are the 2 types of tactical ventilation and through what means can they be achieved
Vertical and Horizontal ventilation can be achieved through Natural, Mechanical, and
Hydraulic means.
What is a consideration when breaking the windows on a structure
Breaking all the windows on a structure
will not increase the ventilation. Instead, it
will only add more air to the fire causing it
to grow. Do NOT break windows unless it is
a planned and coordinated effort with fire
attack or to use the Quick Attack Monitor for transitional attack. Even then you
would only break one window where the fire is in order to knock it down directly
with a straight stream
What is a key point of ventilation?
Keep in mind – ventilation must be
coordinated with Fire attack –
it is a systematic and controlled
process involving coordination
of which areas to ventilate (ex.
breaking windows, opening
doors, roof cuts etc.)
What are 3 types of Mechanical ventilation
Positive Pressure, Negative-Pressure, and Hydraulic
Where the fire exists in an under-ventilated state or
where any warning signs preceding back draft are
apparent, then PPV…
should not be used. It is well
established that the addition of air into an
under-ventilated compartment could possibly
trigger a back draft, smoke explosion or even a
flash over.
What are some advantages of PPV
can be establish without entering contaminated environments
Air currents are kept to a minimum
Equipment does not block doorways
Internal combustion equipment operates more efficiently (gas operated fans)
Equipment cleaning and maintenance is reduced
Noise levels are reduced within the fire building
It is effective in all types of occupancies
Heat and smoke can be directed away from paths of egress
It can be controlled
It is more effective than NPV or HV
What are disadvantages of PPV
Must be coordinated with other sector
Introduces large volumes of air into a structure that if misdirected will intensify
and spread the fire.
Requires special equipment
Depends on a power source (water, electricity, fuel).
When can HVAC systems be utilized to remove smoke
and heat from a specific area in a high-rise
If personnel on site know how to operate the HVAC system.
The HVAC system is capable and design for that purpose
HVAC systems can range from simple manually controlled air movement systems
to very sophisticated automated systems that have smoke removal capability and
smoke control zones.
What type of ventilation is Hydraulic ventilation and when is it used
Hydraulic ventilation is a form of
Negative Pressure Ventilation (NPV). Hydraulic ventilation is
performed by interior attack teams to quickly clear heat and smoke from a room.
If Fire control has not been established,
the use of Hydraulic ventilation may cause the fire to intensify or overtake the attack
crews what can the fire attack crew do in this scenario
However, a fire attack crew inside the compartment on fire can knock down
the flames, then turn the nozzle toward an opening (window) and hydraulically
ventilate the room to get rid of the heated steam caused by hitting the seat of the
fire. This is a great way to knock down a fire and clear a room before outside crews
are set up for ventilation.
How is hydraulic ventilation performed
A fog stream is directed through a window to cover 85-90% of the opening. The
moving water entrains air and generates a negative pressure. Before using hydraulic
ventilation in the fire room, it is important to initiate cooling the environment or hitting
the seat of the fire.
The Sector using Hydraulic ventilation should contact Fire Command prior to
ventilating,
when Vertical ventilation must be established through stairways or hoist ways what order should flow path be established
Open the door at the point of exit first, and then
work your way back to the fire floor ensuring
doors to other floors are closed.
Describe positive pressure ventilation.
Positive pressure - creates differentials in air pressure and forces air out.
Describe negative pressure ventilation.
Negative pressure - fans pull smoke away from the interior.
Describe hydraulic ventilation.
The hydraulic ventilation technique is used by interior attack teams using a fog
stream set on a wide pattern to cover 85% to 90% of an opening. It clears the
interior of smoke and heat by drawing air past the fog stream.
Give four limitations of horizontal ventilation.
Four limitations of horizontal ventilation are listed below:
a. Horizontal ventilation will send the smoke, gases, or heat into the same
corridors that fire fighters and building occupants are using. Rescue
considerations come first.
b. Remember that hot gases rise during ventilation and may ignite
neighboring structures. Make sure charged hose lines are in place before
horizontal ventilation is started - unless the building must be opened to
begin rescue operations.
c. Do not ventilate the windward side of a structure before opening the
leeward side; you may disturb the delicate balance of thermal layers.
d. Do not obstruct the ventilation opening. Remember, air can’t get through
an obstruction, keep low and out of the natural ventilation flow path.
List five advantages of forced ventilation.
Five advantages of forced ventilation are listed below:
a. It is controllable.
b. It can supplement natural ventilation.
c. It is faster than natural ventilation.
d. It reduces smoke damage.
e. It aids in property conservation.
List three disadvantages of forced ventilation.
Three disadvantages of forced ventilation are listed below:
a. It can “feed” the fire with fresh oxygen.
b. It requires a power source.
c. It requires special equipment.
Define leeward and windward.
Windward: the side of the building the wind is striking
Leeward: the opposite side of the building the wind is striking.
In short, fresh air enters a structure windward and leaves it leeward.
List five disadvantages of hydraulic ventilation.
Five disadvantages of hydraulic ventilation are listed below:
a. Water damage to interior increases
b. May deplete water supplies
c. Not suitable for winter climates because of ice production
d. Firefighters have to stay in a contaminated atmosphere to achieve
ventilation
e. Ventilation time relies on SCBA and it’s service time
What factors should you consider when deciding where to ventilate a structure?
The factors that you should consider when deciding where to ventilate a structure
are:
a. Location of the fire-
b. Location of occupants
c. Interior and exterior exposures-
d. Type of construction
e. Purpose or use of occupancy-
f. Extent to which the fire has progressed
g. Condition of the building and its contents-
h. Existing openings
i. Direction of the wind-
j. Available personnel and equipment
Describe both vertical and horizontal ventilation and when they should be used.
Horizontal - Horizontal ventilation is defined as the horizontal channeling of heat,
smoke and gases through wall openings such as windows and doors allowing
cooler air to enter.
a. Horizontal ventilation should be used when:
i. buildings in which the fire is not large enough to require opening the
roof
ii. buildings with windows or doors close to the seat of the fire
iii. buildings in which the fire involvement is below the top floor
iv. Buildings in which fire has not entered structural voids or concealed
spaces.
Vertical - Is defined as the vertical channeling of heat, smoke and gases which is
achieved by creating an opening above the fire either by means of existing
openings or by cutting the roof.
b. Vertical ventilation may be used in the following cases:
▪ Buildings with fire in the attic, the cockloft, or the top floor
▪ Windowless buildings with few exterior doors
▪ Buildings with large vertical shafts
▪ Buildings in which fire has entered structural voids or concealed
spaces.
Describe forced ventilation.
Forced or mechanical ventilation involves the use of fans, blowers, nozzles, and
other mechanical devices to create or redirect the flow of air inside an involved
space. Forced ventilation removes or reduces the effect of unstable and erratic
winds. It provides a dependable, controllable airflow that gives us, greater control
of heat and smoke movement.
True or False. Trench ventilation is an offensive form of ventilation.
False: Trench ventilation, is a defensive form of ventilation
List some of the safety precautions for vertical ventilation.
a. ALWAYS REMEMBER THAT YOU ARE WORKING OVER THE
FIRE.
b. Always wear full PPE and SCBA.
c. Understand building construction and the effects of fire on the type of roof
construction.
d. Know the location of the fire, the wind direction and smoke conditions on
the roof.
e. Continuously read the roof for construction and weakness.
f. Continuously observe the safety of roof crews.
g. Evacuate the roof once ventilation has been established.
h. Always test the roof by sounding.
i. Observe overhead wires near the roof.
j. Obstructions or dead loads on the roof.
k. Snow and Ice create fall hazards as well as increasing the dead load on the
roof and obscuring signs of roof weakening.
l. Parapet walls create fall hazards onto untested roofs.
m. Roof collapse (partial or complete).
n. Maybe necessary to breach ceiling to accomplish ventilation
o. Work on the windward side of the hole
List some problems you may face with Hi-rise ventilation?
o Increased occupancy that is exposed to heat, smoke and fire gases
o Fixed windows may alter the most efficient ventilation flow path.
o Increased logistical issues – greater amount of door control, required
manpower and equipment for effective ventilation.
o More time is required to establish ventilation due to the size of
structure.
What is mushrooming?
Is the lateral and downward migration of smoke when it encounters a
physical barrier
Definition of Ventilation
Ventilation, as applied to firefighting, is the
planned and systematic release and removal of
heated air, smoke, and toxic gases from a confined
area and the controlled replacement of these
products of combustion with a supply of cooler,
fresh air.
