14 Special Vent Ops Flashcards
Physical exertion of crews to reach the fire floor will mean
They may have less energy to perform firefighting functions
Truck crews should never enter high rise empty handed. Of they aren’t carrying forced entry tools or vent equipment they should have
Space Scba cylinders
Hose
Tools
Lights
Moving large amounts of tools is generally coordinated by those assigned to
Lobby control
Low rise elevators
Floors 1-10
Mid rise elevators
Only floors between low and high elevators ex, floor 1 and floor 10-20
Highrise elevators
Serve only upper floors, ex.. Floor 1 and 20-30
Express elevators
Ground floor to upper most floor. Ex. Floor 1 and 31 or whatever highest floor is
Freight elevators
Serve some or all floors
Freight elevators should be used whenever possible if approved by officer in charge because
They can handle the additional weight of ff’s in full ppe along with extra tools and equipment, weighting more than a ton
Dangers of using elevators in a fire
Malfunction or damage from heat could recall elevator car to the fire floor or strand the elevator between floors in the shaft.
Fire behavior in highrises is mostly affected by
Stack effect and mushrooming
Stack effect
Natural vertical mvnt of air, or heat and smoke, in tall structures based on differences of air density inside and outside the buildings due to temp differences. Strong vertical column of mvnt.
With the stack effect, the greater difference between the inside and outside temp and the greater the building height,
The greater the stack effect will be
If temp is lower outside and hotter inside highrise the stack effect moves up. If it’s hotter outside and cooler inside it moves
Down and out, called reverse stack.
Mushrooming, aka ceiling jets
Smoke rising until it hit barrier, then move horizontally until same. Then banks down and fills
When smoke reaches the same temp as ambient air in the highrise, it loses its buoyancy and
Stratifies, forming layers of smoke in the building.
Stratification can occur near the top floor and
Or several floors down below.
Most ppv positioned at street level are only effective up to how many floors up
22
If the building is higher than 22 floors, how do you vent with fans
Add more fans at the 22 floor or around there, or add smoke ejectors at the top most floor to be vented, or both
Highrise vent options
Vertical or top ventilation
Horizontal fire floor
Horizontal above and below fire floor
If vertical vent may endanger fleeing occupants, what might have to be used
Horizontal vent
Fire and smoke should be vented vertically through stairwells and other vertical shafts, taking advantage of
The stack effect
Vertical venting in highrises can prevent
Mushrooming on upper floors and does not promote lapping
One of the biggest challenges to vertical or top venting is
Getting ff and equipment to the roof
If the roof is within reach of an aerial on a highrise, it is the preferred method for
Moving manpower and equipment to the roof for venting
If an aerial does not reach the roof, how can it be used to gain access
Reach the farthest floor it can, enter through a fire escape or window and use stair and elevators the rest of the way to the roof
Although highrises usually have more than one stairway, few have more than one that
Terminates at the roof.
During a fire, a stairwell can be relatively free of smoke but congested with
Occupants, attack lines and ff
One stairwell must be dedicated to attack and the other to
Evacuation
Elevators that service the fire floor or floors above should not be used unless
The officer in charge of the fire floor deems it safe to do so.
If a bulkhead or penthouse is used to ventilate the stairwell that terminates at the roof, the door should be blocked open because
If it closes it could change the vent profile dangerously
Ventilation in the stairwell that terminates at the top floor should be delayed until
All occupants have been evacuated or on an area of refuge
Firefighters should be clear of the vent stairwell prior to venting because
Once it is opened, the stairwell can become untenable
If buoyancy is the only force acting on gasses within a closed compartment, then in relation to atmospheric pressure, the pressure will be what at the top
Higher at the top and lower at the bottom
Neutral pressure plane
Point in a highrise where interior pressure equals atmospheric pressure outside, moves up or down depending on wind and temp. May be in middle of building
The neutral plane in a building without gasses being vented or openings made is where
Between 35-50% of the building height.
In extreme distances between the neural plane, if openings are made at the top and bottom of a structure, the escape of high pressure at the top and inward pull of air at the bottom Causes
The entire building to act as a chimney, stack effect
When air is pushed in a building by ppv it causes high pressure in the compartment and does what to the air
Forces it outside where there is lower pressure
By dragging smoke out of a building with a smoke ejector, it causes negative pressure inside the compartment and
Forces the air out while dragging higher pressure air in from outside
What can raise or lower the neutral pressure plane
Wind
If the fire is above the neutral plane, if vented on the leeward side of the building it will
Vent naturally because the leeward side outside is lower pressure and the fire is in the higher pressure zone of the building
Opening a window below the neutral pressure plane may
Draw air inside the building rather than allow smoke out of it, spreading fire
The closer ventilation takes place near the neutral plane,
The less effect, positive or negative, wind will have on it
Venting below the fire is not common but may be needed when smoke has spread to lower floors because of
Reverse stack effect
Venting floors below the fire can be facilitated by
Using ppv blowers or other fans
Venting on the fire floor first requires a knowledge of building layout because
Venting a dead end corridor or into a shaft that doesn’t exit can cause vent problems or extension
Horizontal venting on the fire floor should be done only when there is no other choice because
It can be Time consuming because of window construction, and dangerous to people on the street below
To avoid hazards associated with horizontally venting sealed highrise buildings, what should be done
Vertical vent whenever possible.
Vertical venting can be accomplished on intermediate highrise floors by
Venting smoke across the fire floor to the stairwell that reaches the roof. Maybe with assistance from fans.
Venting above the fire will be most effective if the ok rices is started where
At the top of the building. Provides clear path out, and starting on the fire floor marry increase damage and put vent crew in danger
Smoke dampers
Control airflow in hvac units, usually activated by fire alarm signaling system
The actual manipulation of hvac system for smoke control should be left to
The building engineer, who much be available to IC for reference in venting under fd direction
Guidelines for effectively using hvac system to control smoke mvnt
Operated only by building engineer
Used to assist locating seat of fire
Use to limit fire extension and smoke to smallest area possible
Should not be allowed to spread fire or smoke beyond area of origin
Provide fresh air to trapped occupants in refuge areas
To accomplish manual shut down of smoke dampers with the least delay, building engineer should be contacted when
As soon as the fd arrives
Curtain boards
Vertical boards, fire resistive half walls that extend down from roof to limit spread of fire and smoke
Nfpa 204
Standard for smoke and heat venting
Automatic roof vents are intended to limit the spread of fire within a building by
Releasing heat and smoke into the outside before it mushrooms
Because automatic roof vents work on their own, it may reduce or eliminate the need for
Additional vertical venting
Automatic roof vents may be activated by smoke detectors but otherwise, most still operate using
Spring loaded or counterweight cover assembly with fusible link activator
Prevailing winds may prevent automatic roof vents from working, this may require
The vents to be closed and horizontal used instead
Sprinklers operating near roof vents may not allow heat to activate them, firefighters should not try to force open vents because it can damage them, but rather they should
Be familiar with manual controls
Highrise fires present numerous challenges, including
Limited access Large number of offices or apartments Heavy occupant loads Falling glass or debris Rapid smoke and fire spread through shafts Locked interior doors Low water pressure Climbing a lot of stairs
Monitors are primarily intended to increase natural light in a building but may also provide
Natural ventilation
Most monitors have wires glass or glass panels sloping down from their ridge as a roof and rely on what for ventilation
Rely on the glass breaking for vent
Monitors with solid walls may have panels hinged at the bottoms with fusible links to
Open automatically from gravity when fire needs to vent
Curtain are intended to confine the fire to an area over its source, the walls generally extend how far
A distance of at least 20 percent the vertical distance from the floor to roof but no lower than 10 feet
Curtain board may help accelerate the activation of
Sprinkler heads over the area of origin
Usually but not always, cellars will have no windows and basements will have
Small windows between grade level and first floor
Early ventilation of fire below grade is critically important to firefighting operations because
Pipe chases, shafts, chutes etc can contribute to fire spread on upper floors
If an opening in a basement can be made opposite the interior entry point, the fastest way of venting may be
Ppv in the interior point of entry as crews enter with a line.
If no openings can be made in a cellar how do you vent
Cut a hole on the first floor near a window and position a smoke ejector to facilitate vent
Windowless building require what type of vent
Fast vertical vent to prevent backdraft
