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
When reading smoke what is the relation between volume and velocity
“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.
