SOGs-17-Ventilation Flashcards
What is the definition of flow path?
Movement of heat and smoke from the higher pressure within the fire area toward the lower pressure.
If the thermal layering is disturbed blocked etc. hot air will travel out on top and cool air will travel in on the bottom
What is the definition of fuel limited?
The heat release rate of the fire is limited primarily by the chemical and physical characteristics of the available fuels.
Define hydraulic ventilation
Using water flow to draw the air out of a structure
Define mechanical ventilation
Using machinery and/or devices to assist in the movement of air like positive pressure fans and building systems
Define natural ventilation
Allowing air to naturally move without any assistance lake wind opening windows creating openings at the highest point of the structure
Define tactical ventilation
The planned systematic and coordinated removal of heat smoke and fire gases and the replacement with cooler fresh air
Define vent limited
A fire in which heat release rate and fire growth are regulated by the available oxygen within the space
What are some indicators of a fuel limited fire?
Indicators may include: An incipient or early growth fire High neutral plane Better visibility Relatively low temperatures
What are some indicators of a vent limited fire?
Fire is beyond incipient stage
Mid to low neutral plane
Poor visibility
Flames exiting outside a window or door
Air drawn into the fire when doors are opened
Increased temperatures but will be declining if in decay stage
All common Backdraft indicators
What is a ventilation profile?
The ventilation points showing the flow paths of heat and smoke out of the structure as well as any air movement into the structure
What should be considered when determining a structure’s ventilation profile?
Existing and/or potential flow path The location and stage of the fire Fuel or vent limited Wind direction Exposures Rescue or suppression Building layout and construction Integrated ventilation systems Smoke conditions: volume velocity density colour
What is the purpose of door control?
Controlling fresh air flow to feed a developing fire by opening or closing a door.
Closing a door immediately upon arrival will help control the heat release rate of the fire
What should be considered when choosing your tactical plan for ventilation?
Tactics that complement the IAP
The location of personnel committed to interior operations
Occupant location
How tactics may affect flow paths, fire behaviour and operational time frames
When is any PPV usage utilized?
After fire control
After PPV operations when should consideration be made of discontinuing the use of the fan?
When checking for extension
Where should a PPV fan be placed?
For complete airflow coverage of the inlet
Define backflow as it relates to a PPA?
Pressurized air coming out at the inlet point
Define transitional attack
Offensive fire attack initiated by an exterior indirect hand line operation into the fire compartment to initiate cooling while transitioning into interior direct fire attack in coordination with ventilation
What needs to happen if a positive pressure attack is initiated and heavy smoke or fire is exhausting out the inlet point?
Create a larger/additional exhaust
Throttle down the fan; reattempt
What considerations should the IC consider prior to committing to a PPA operation?
360 size up has been completed
Flow paths have been determined
Confirm any VEIS operations are complete and protected themselves and the occupant
Fire location is determined
Fire does not involve the structure
Minimum two crews on scene
Exhaust locations have been determined
Where should fans be placed for a positive pressure attack?
The point of entry from the unburned side of a fire
2 m back from the entry point
Create a pressure ”cone” effect around the door
What are the three basic terms when deciding whether to continue with the PPA attack or terminate it
Improves the atmosphere - continue with it Makes no change - review all aspects, re-position if necessary Worsening atmosphere - discontinue its use
What is the preferred flow path if available?
Upwind to downwind
What is the preferred tactical consideration for a positive pressure attack?
Combining a transitional attack simultaneously with a PPA
How long should personnel wait for the fan to input into the structure before entering?
30 to 60 seconds
If possible what should the exhaust outlet ratio be for a positive pressure attack
2:1 to the entry or at a minimum 1:1 to the entry
What may occur at the exhaust as a result of positive pressure?
A blow torch effect
What type of chemicals or environment is not conducive to a positive pressure attack?
Class B chemicals
Potential for a dust explosion
Larger, open spaces, high ceilinged structures
Define evacuation stairwell
Stairwell utilized for evacuation operations generally suitable for civilians
Define operations stairwell
Stairwell utilized for firefighting operations with possibly propped open doors generally unsuitable for civilians
Define set up as it refers to high rise ventilation?
Two fans in series one placed in front of the other approximately 1.5 to 2 m between them
What is a stack affect as it refers to a high-rise ventilation?
Also known as a chimney effect is the movement of air into and out of buildings, chimneys, flu gas stacks, or other containers, resulting from air buoyancy.
What is a ventilation sector officer (VSO)?
Officer of an apparatus designated to plan and coordinate ventilation of a structure
What is said about air buoyancy as a result of a stack effect or chimney effect?
The greater the thermal difference and the height of the structure, the greater the buoyancy force and thus the stack effect
What is the responsibility of a third arriving apparatus at a high-rise structure fire?
Unless otherwise assigned or directed begin to set up for ventilating
What is done if the third arriving apparatus is assigned other duties at a high-rise structure fire?
The IC shall designate an apparatus to complete the ventilation set up
True or false: entry control operations are to be conducted by a third driving apparatus of a high-rise emergency
False: third apparatus personnel shall set up at the exterior exit of the operation stairwell and not be expected to conduct entry control ops
Once set up has been established at the operation stairwell what do the 4 apparatus personnel do next?
2 members have begun the ascent to upper floors
2 remaining personnel move to the evacuation exit stairwell and perform an identical set up as done at the operations exit
If only 1 personnel remains contact IC for additional assistance
What are the two members of the third arriving apparatus at a high-rise structure fire who have begun the ascent to upper floors trying to determine?
Effectiveness of the ventilation/pressurization efforts
Assisting/redirecting evacuating occupants
Assisting/rescuing found occupants and fire personnel
Observing heat and smoke conditions on all floors (only report significant conditions)
Locating exhaust points (roof hatches, etc)
Removing immediate smoke from upper stairwells
What are the options for ventilating once a fire is contained to unit of origin in a high rise structure fire
Area of origin - through a door/window
Across/nearby the area of origin
Roof access
Smoke shafts
How are smoke shafts utilized for ventilation?
Utilizing existing smoke shafts if equipped to remove the smoke
How is the area of origin used for ventilation?
Utilizing windows and/or doors using pressurize stairwells and subsequent hallway to move the smoke out through the area of origin
How is across/nearby the area of origin an option for ventilation
Utilizing windows and/or doors in an area nearby the area of origin using the pressurized stairwells and subsequent hoping to move the smoke out through an area nearby the area of origin
How was roof access an option for ventilating?
Utilizing an established exhaust to remove the smoke (roof hatch/mandoor)
What needs to be considered when determining the best option for ventilating a high-rise structure?
Natural wind
Stack effect
