Chapter 13 - Ventilation
`Vertical Ventilation occurs after the IC has determined many things, to include
-"Moved personnel and tools to the roof"
`When cutting an exhaust opening in any type of roof for Offensive Ventilation Methods , there are two critical points to bear in mind; which are
-A square opening is easier to cut and repair afterwards -One large opening is better than several smaller ones
`The need to use mechanical or natural ventilation is indicated when:
-After the location & size of fire has been determined -Layout of building is not conducive to natural venting -Natural Ventilation needs support -Fire burning below ground within the structure
`There are many factors to consider on where to being TV, to include;
-Availability of existing roof openings -Extent of fire progress -State of FF attack crews -Protecting means of egress
`HEAT indicators include;
-Blistering paint -Bubbling roof tar -Crazed glass (From rapidly "decreasing" temperatures) -You can sometimes feel a difference in the structures temperature on you skin from a distance.
`There are many factors which determine whether TV should begin; to include;
-Building Construction -Type of Ventilation -Location of Ventilation -Weather Conditions -Exposures -Staffing and available resources
`The disadvantage of Mechanical Ventilation include:
-Can cause fire to intensify and spread
`Discuss some of the characteristics of older home typical layouts
-Composed of smaller compartments -Windows that could be opened for ventilation -Empty wall cavities depending on air pockets to provide insulation
`How do you vent a Pitched Roof with shingles
-Cut a few inches below the peak on the leeward side -Always cut the hole at or near the peak -Work from an apparatus for very steep roofs
`Discuss how to make a Louver Cut
-Cut a rectangular hole no smaller than 4' x 8' -Make short cuts across top & bottom of the rafter -Then make parallel to the rafter -Strike the near side to make it loose from the rafters -Pull the far side towards you with a roof hook
`How to cut a Trench Cut
-Cut two parallel cuts from one exterior wall to the opposite exterior wall. -Remove the roof material between the cuts -Push down on the ceiling below -The distance between the cuts should be large enough to prevent fire form burning past the opening, and small enough that it does not compromise the integrity of the roof. A typical trench cut is about 3 - 4' wide
`There are many reasons to perform TV, to include;
-Decreasing rate of fire spread -Improving firefighter efficiency -Improve victim survival potential -Reducing smoke and property damage
`Airflow is "caused" by the following
-Different densities between hot smoke and cool air -Pressure differentials inside and outside the compartment
`Name the non-obvious responsibilities of the roof team leader
-Directing efforts to minimize secondary damage -Coordinating roof team efforts with interior FF's -Assemble roof teams of at least two, but with no more than necessary above that
`AIRFLOW is the movement of air towards burning fuel AND movement of smoke out of the compartment. Airflow indicators include;
-Direction of air/smoke -Velocity of air/smoke -Turbulence of air/smoke -Movement of the neutral plane
Ventilation requires many safety precautions to include:
-Evacuate the roof promptly when ventilation work is complete or when ordered to leave -Use lifelines and ladders to guard against falling -Start power tools and test before climbing, turn off when climbing -Extend ladders 3-5 rungs above roof edge and SECURE ladder to wall or roof. -When operating from aerial platforms, the floor of the platform should be even with, or slightly above, roof -Fire ladders are only meant to prevent slippage and are not intended to be used on fire weakened roofs -Never direct hose streams into vertical openings when FF's are inside, because it can force smoke, heat, and steam down on them.
`What are some of the common factors that can reduce the effectiveness of vertical ventilation;
-Fire streams directed into ventilation openings -Explosions -Burn through of the roof, floor, or wall - -Additional openings the attack team and upper openings
`There are several disadvantages to Hydraulic Ventilation, such as
-Increased water damage if done incorrectly -Will reduce available water supplies -In cold wx, there will be an increase in ice amounts -FF's must remain in heated and contaminated area -Operation may be interrupted if FF's need new tank air
`There are many advantages of PPV over NPV, to include;
-It is equally effective with Horizontal or Vertical Ventilation because it supplements natural air currents -More efficient -"The velocity of air currents within a building is minimal and creates little, if any, effects that disturb the building contents or smoldering debris. -Easier cleaning than cleaning negative pressure fans -Effective in all types of buildings, especially in large, high ceiling areas -Heat and Smoke may be directed away from unburned areas or away from egress paths
`Name some of the typical characteristics of more modern homes
-Larger open spaces -Higher ceilings -Atriums -Lightweight manufactured structural components -Sealed windows -Synthetic Insulation -Better energy-efficient designs tend to contain fires for longer periods of time; creating fuel rich environments, which are magnified in large-are residential structures.
To ensure effective PPV operations, many things should be done, to include
-Maintaining communications between the IC, interior attack crews, and the PPV operator
`Discuss the deference between Offensive Vertical Ventilation and Defensive Vertical Ventilation
-Offensive Vertical Ventilation: Intended to aid in reaching and extinguishing the fire -Defensive Vertical Ventilation: Meant to stop the spread of fire and contain it in one area of the structure The IC must access the risks, implement safety precautions, and determine which ventilation to use, Offensive or Defensive
`Safety considerations for a making a trench cut include;
-Plan ahead -Have a charged hose line present -Have two means of escape, located remotely from each other and do not require crossing the trench cut. -Assign a roof safety officer to oversee the operation -Cut small inspection holes a few feet from the trench cut on both the fire side and the working side. These holes will serve as indicators as to when the fire approaches and also show if the fire has breached the trench cut.
`The advantages of Mechanical Ventilation include;
-Reduces smoke damage -"Promotes good public relations"
`Discuss some areas of concern when using roof/floor sounding techniques
-Roofs with several layers of covering may not respond accurately with sounding tactics by FF's -Tile and Slate roofs are not conducive to sounding and must be removed to reveal the underlying structure.
`How do you vent Arched Roofs
-Same as flat roofs -As soon as you are on the roof, make a Kerf Cut and locate the arches, observe the truss space, and determine fire involvement before proceeding further. -Only walk on the trusses and other strong points when possible
`How do you vent a Pitched Roof with slate or tile
-Slate and tile roofs may be attached to solid sheathing or to battens (Strips of wood attached to the rafters) -Slate & Tiles roofs must be opened by removing them or using a large sledge hammer. Battens may not need to be cut if space between them does not interfere with venting.
`FIRE BEHAVIOR INDICATORS `What are visible observation categories that can give you clues on how to begin, or adjust, TV operations
-Smoke color -Air Flow -Heat -Flame
`There are several things to look out for when accessing the strength of a roof, to include;
-Smoke coming from the roof -Note: Some roofs are normally spongy
`Successful TV depends upon many things, such as;
-Systematic application of procedures for removing contaminants
`FLAME can provide indications of;
-The size and location of the fire The stage of a fire and whether its Ventilation Controlled or Fuel Controlled are primary considerations of TV procedures.
`There are several disadvantages to PPV, to include;
-The structure must be intact -Interior carbon monoxide levels may increase if using a fueled operated fan -Hidden fires could be accelerated and spread
`How do you vent Metal Roofs
-Thin metal roofs can be cut with saws and axes -Thicker metal roofs can be with metal cutting tools or power saws with metal blades -Consider using skylights, monitors, or scuttle hatches as vents instead of cutting thick metal roofs when possible -Older buildings may have large pieces of sheet metal over skip sheathing. These can be cut power saws or axes.
`The following observations about SMOKE, taken together, can help obtain a clearer picture of the actual interior fire conditions
-Volume of smoke discharge -Location of smoke discharge -Smoke color, density, and pressure -Movement of smoke
`Structures that make good candidates for horizontal venting include:
-fires not involving the attic/cockloft -Multistory buildings with no fire in the top floor -Building too weakend by fire -Buildings with daylight basements -Buildings with ineffective vertical ventilation
`What is the minimum distance a Trench Cut should be made in front of a advancing fire
30' and only after a offensive vertical opening has been made to allow heat and smoke and the trench cut to be made to be completed before the fire front reaches the trench cut.
`How far away should you set the fan for a normal 36" Doorway to conduct positive pressure
4 to 6 Feet away. It is important that the whole cone of air created by the blower covers the entire doorway. It is also important to control the location and number and size of other exterior openings.
`How many more FF's are usually needed to conduct fire fighting operations and search and rescue operations in high-rises as compared to lo-rise buildings
4 to 6 times as many FF's required
`How much area of the door or window should be penetrated with the fog stream for the most effective Hydraulic Ventilation, and about how far should the nozzle tip be from the door or window
85 - 90% Nozzle Tip should be 2' away from the door or window. The larger the opening, the faster ventilation will occur. Master Stream devices can be used in large structures; such as commercial or industrial doorways and loading docks.
`Kerf Cut
A single cut the width of the saw blade made in a roof to check for fire extension. Keep in mind that a major disadvantage to Kerf Cuts is the possibility of melting roofing materials sealing the Kerf Cut closed again.
`Name the path areas of an air flow
An inlet vent where air enters A flow path (typically through the fire area) An outlet or exhaust vent
`Mechanical Ventilation
Any means other than natural ventilation. This type of ventilation may involve the use of blowers and smoke ejectors. It can be used for both vertical and horizontal ventilation. But is used most often for horizontal. It is accomplished through Negative-Pressure or thru Positive Pressure.
`Horizontal Ventilation
Any technique by which heat, smoke, and other products of combustion are channeled horizontally out of a structure by way of existing or created horizontal openings such as windows, doors, or other openings in walls. Typically portions of one or more of the horizontal openings will also serve as an air inlet.
`Before selecting a place to ventilate, what information should be gathered
As much information as possible about the fire, the building, and occupancy.
`HIGH-RISE FIRES `Discuss how the likelihood of high occupancy rates in high-rise building affect the priorities of fire fighting
Because of the high occupancy rates, Life Safety Considerations are an even higher priority
`Discuss the main problem in using PPV in above ground operations
Coordinating the openings and closing of doors in the stairwells being used to ventilate the building. To control openings and pressure leaks, one person should be placed in charge of the pressurizing process. It is helpful to use portable radios and have firefighters patrol the stairwell and hallways
`Discuss Positive Pressure Ventilation
Creates slightly higher pressure inside the building, causing smoke and heat inside the building to exit through openings to the lower-pressure area outside. Positive Pressure Ventilation requires good fireground discipline, coordination and tactics
`What is a last resort technique that can be used to ventilate a basement
Cut a hole in the floor near a ground level door of window. The heat and smoke can then be drawn out of the basement and pushed/sucked outside using fans.
`Discuss when you should cut inspection holes into roofs
Cut inspection holes before cutting any type of ventilation hole.
`Name the ways that TV can move airflows
Decide if it is best to deploy TV with a horizontal ventilation or a vertical ventilation. Also, keep in mind that there is Natural Ventilation and Mechanical Ventilation.
`Between the years of 1973 and 2008, the footprint of building lots has increased or decreased by how much
Decreased 25%; which, reduce FF access and increases Exposure risks.
`Trench Ventilation
Defensive tactic that involves cutting an exhaust opening in the roof of a burning building, extending from one outside wall to the other, to create an opening at which a spreading fire may be cut off. Also known as Strip Ventilation
`Discuss Property Conservation objetives
Effective salvage operations can begin outside the the immediate area of the fire even while fire control operations are being conducted
`Blowers
Fans that are used to push fresh air into a structure. They may be powered by electricity, gasoline engines, or hydraulically. Blowers that are not intrinsically safe may only be used to push fresh air into the structure.
`There are many types of tools and equipment required to TV, to include;
Flexible ducts, stacking devices, hanging devices
`Define Flow Path
Flow paths are air flows connections between the air inlet and outlet.
`Between the years of 1973 and 2008, the footprint of houses has increased or decreased by how much
Has increases over 150%
`Discuss TV in a basement
If the basement has windows, or below grade window wells, horizontal ventilation can be employed effectively
`Exhaust Opening
Intended and controlled exhaust locations that are created or improved at or near the fire to allow products of combustion to escape the building.
`When a Trench Cut is created improperly, what can happen
It "will" place FF's in a very dangerous position, working ahead of the fire. Also, it may cause the fire to sprea more rapidly and potentially destroy the whole structure
`Offensive Ventilation Methods
It involves making an opening over the seat of the fire at or near the highest point of the roof.
`Discuss Life Safety objectives
It is the highest Priority Safely increase oxygen levels Creating smoke-free paths of egress
`Discuss Negative-Pressure Ventilation (NPV) operations
It is the oldest type of mechanical ventilation. After placing a smoke ejector in an opening (Door, window, wall cut), you must cover/seal any open space between the ejector and the border of the opening in order to prevent recirculation. When venting potentially atmospheres, only intrinsically safe smoke ejectors and electrical connections should be used
`What determines the size of an Exhaust Point
It varies with the size of the Entry Point and the capacity of the blower used. The Entry Point needs to be opened up first and before blowing air into an Entry Point
`How should a roof ventilation team keep in contact with the IC
Keep in Constant communication
`Name the different types of Inspection holes
Kerf Cuts - The easiest and fastest. "A" Cuts or Triangle Cut Kerf Cuts can be done with axes or power saws.
`When correctly implemented, TV helps achieve the three incident priorities, which are;
Life Safety, Incident Stabilization, property conservation
`Does low pressure or high pressure usually exist under a neutral place
Low Pressure.
`Positive-Pressure Ventilation
Method of ventilating a room or structure by mechanically blowing fresh air through an inlet opening into the space in sufficient volume to create a slight positive pressure within and thereby forcing the contaminated atmosphere out the exit opening.
`Recirculation
Movement of smoke being blown out of a ventilation opening only to be drawn back inside by the negative pressure created by the ejector because the open area around the ejector has not been sealed
`What is the survivability in rapid fire development
None. Not for firefighters or civilians
`When should TV take place
Once fire attack hose lines and teams are in place and ready to advance toward the fire.
Stack Effect
Phenomenon of a strong air draft moving from ground level to the roof level of a building. Affected by building height, configuration, and temperature differences between inside and outside air. Fire, smoke, and toxic gasses can spread rapidly through pipe shafts, stairways, elevator shafts, etc. This creates upward drafts which can interfere with evacuation and ventilation
`Leeward Side
Protected side; the direction opposite from which the wind is blowing.
`Triangle Cuts (A Cuts)
Provides the most reliable information of conditions beneath the roof. Can be created from a single Kerf Cut. Create A Cuts by: 1st cutting a diagonal cut from upper left to lower right \ 2nd cut from the top of the first cut to the lower left /\ 3rd cut along the bottom two ends. /_\
`Louver Cut or Vent
Rectangular exhaust opening cut in a roof, allowing a section of roof deck (still nailed to center rafter) to be tilted, thus creating an opening similar to a louver. Also called center rafter cut.
`Define Ventilation
Removal of heated air, smoke, and fire gasses from a structure and replacing them with cooler air; allowing firefighters to perform search and rescue along with fire suppression operations. Decreases the rate of fire spread and increases visibility
`Discuss freshair "entry" through a doorway of a structure fire
Sometimes fresh air (low pressure air) will enter through the lower portion of the door, under the neutral plane; while hot air (high pressure air) will exit out the top of the door frame. But in some cases the freshair will enter through the entire doorway. Roof vents may be the primary outlet in this situation.
`What are the most common types of openings made on flat roofs when using Offensive Ventilation Methods
Sqare or rectangle are the most common. These preferably are made between to ceiling trusses or made with the exposed truss in the middle of the cut
`Negative-Pressure Ventilation
Technique using smoke ejectors to develop artificial circulation and to pull smoke out of a structure. Smoke ejectors are placed in windows, doors, or roof vent holes to pull the smoke, heat, and gases from inside the building and eject them to the exterior.
`Natural Ventilation
Techniques that use the wind, convection currents, and other natural phenomena to ventilate a structure without the use of fans, blowers, and smoke ejectors. It uses the buoyancy of heated smoke and gases to draw them out of the structure through roof openings while entrailing fresh air into the structure.
Horizontal Smoke Spread
Tendency of heat, smoke, and other products of combustion to rise until they encounter a horizontal obstruction. At this point they will spread laterally (ceiling jet) until they encounter vertical obstructions and begin to bank downward (hot gas layer development)
`Who has the authority to order or stop TV
The IC
`What do you all the location where the Positive-Pressure Blower is placed
The entry (inlet) opening, or point.
`Define Tactical Ventilation (TV)
The planned, systematic, and coordinated removal of heated air, smoke, gases, or other airborne contaminants from a structure, replacing them with cooler and/or fresher air to meet the incident priorities of life safety, incident stabilization and property conservation.
`How do you ventilate if the basement has not windows
Then interior ventilation must be employed. Natural paths; such as up stairways or hoistway shafts, can be used to evacuate heat and smoke, if there is a way to then expel the heat and smoke to the atmosphere without placing portions of the building in danger.
`Smoke Ejectors
These are electrically powered fans that have intrinsically safe motors that are placed in the smoke-filled atmosphere to push the smoke out. They can also be used to push fresh air into the structure. They require the use of electrical power cords and generators to operate.
`BASEMENT FIRES `Discuss Basement fires
They can be among the most challenging situations FF's will face. Unless the basement has vents installed, heat and smoke will quickly spread upward into the structure. Some basements have hoistways (small elevator) that can be used to gain access.
`Discuss Incident Stabilization objectives
To reduce interior temperatures, extreme fire behavior, and fire spread. As well as, controlling and extinguishing the fire by using stages of attack; -Locating the fire -Confining the fire to a room, area, or original structure -Extinguishing the fire -TV can reduce the amount of water needed and help reduce water damage.
`HYDRAULIC VENTILATION
Used to clear a room or building of smoke, heat, and gases AFTER a fire has been controlled. Using a Fog Stream out a door or window Can be used when other types of Ventilation are unavailible.
`Vertical Ventilation
Ventilating at a point above the fire through existing or created openings and channeling the contaminated atmosphere vertically within the structure and out the top. Done with openings in the roof, skylights, roof vents, or roof doors.
`Hydraulic Ventilation
Ventilation accomplished by using a spray stream to draw the smoke from a compartment through an exterior opening.
`Discuss ventilation techniques in windowless buildings
Ventilation in this type of building can be difficult, and the problems involved vary depending on the size, occupancy, configuration, and type of construction materials used. It usually require mechanical ventilation. These buidlings HVAC equipment can sometimes effectively clear the smoke by itself. However, unless the system was designed for this specific purpose, other less effective systems will probably only aid in the spread of the fire. HVAC systems need to be brought under fire department control prior to fire operations
`Discuss the preferred way to use Natural Ventilation
When directed by the IC, open doors and windows on the leeward side of the structure first to create an exit point. Then open doors and windows on the windward side to permit fresh air to enter and force smoke towards the exhaust openings.
`Why is ventilation so critical for basement fires
Without effective ventilation, access into the basement is difficult because FF's would have to descend through the intense rising heat and smoke to access the fire.
`In most cases, is it safer to turn power saws off when transporting them to or from the point of operation
Yes, safer to turn them off, especially on ladders.
`ROOF SAFETY What are some good ways to provide additional footing on a roof
You can use a Halligan, Roof Ladder, or Rubbish Hook
`What are the available means used to perform Horizontal and Vertical Ventilation
You can use; Natural, Mechanical, or Hydraulic Ventilation
`Windward Side
the side or direction from which the wind is blowing.
