Chapter 13: Ventilation Flashcards
Introduction:
What is Ventilation?
The controlled and coordinated removal of heat and smoke from a structure. Effective ventilation not only removed heat and smoke, but it also replaces the escaping gases with cooler, cleaner, and oxygen-rich air.
Before FF’s open a door, take out a window, or cut a hole in the roof, what three questions should you ask yourself?
- Why am I ventilating?
Am I providing a tenable atmosphere for a potential occupant or am I creating a more tenable atmosphere for firefighters?
- Where do I want to accomplish the ventilation?
Horizontally or Vertically?
- When do I want to perform the ventilation?
Hint: When, Where, & What?
Have I coordinated my efforts with the actions of the suppression team and the search and rescue teams?
According to John Norman, what are the two main reasons for performing ventilation?
- Venting for fire. (Venting to allow attack teams to enter and operate within the structure).
- Venting for life. (Venting a specific area to provide fresh air for trapped occupants to breathe and to improve visibility while searching).
Ventilation and Fire Behavior:
What is Neutral Plane
The interface at a ventilation opening, such as a doorway or a window, between the hot gas flowing out of a fire compartment and the cool air flowing into the compartment where the pressure difference between the interior and exterior is equal.
What is Flow Path?
The area(s) within a structure where heat, smoke, and air flows from areas of higher pressure to areas of low pressure. Through doorways, window openings, and roof openings. The flow path is determined by the building design in which doors and windows are opened to outside. Every new ventilation opening may provide a new flow path to the fire and vice versa.
The Impact of Door Control:
“Manning the door”
When making an interior fire attack or rescue effort, maintaining control of the door and keeping it closed as much as possible and opening the door just enough to allow the hoseline to be advanced to the fire.
The Impact of the Ventilation Location:
The location of the ventilation opening has an impact on the growth of the fire. It influences two things. What are they?
Ventilation should occur as close to the fire as possible. Whether it’s directly over the seat of the fire or to open a door or window that will release heat and smoke from the fire directly from the exterior.
Ventilation directly over the fire produces the fastest impact on the behavior of the fire and will exhaust the greatest amount of combustion products, however, without a coordinated fire attack (water application), the results of the fire will not grow, due to the added oxygen. The application of water absorbs some of the heat produced by the fire and can help to remove more energy than the fire is creating.
- It influences how fast a fire reacts to changes in ventilation.
- It determines how effectively the hot gases and smoke are removed from the fire location.
The Impact of the Ventilation Hole Size:
Larger vertical ventilation openings do not localize the growth of a fire. In addition, vertical ventilation alone does not reduce the temperatures in a fire building.
Although vertical ventilation by itself does not appear to have a positive effect on a ventilation limited fire, vertical ventilation in coordination with an exterior or interior application of water as close to the fire as possible, has the effect on improving visibility, reducing the temperature in the fire compartment, and temporarily limiting the growth of the fire.
The Impact of Wind:
Anytime a window or door is opened on the side of a building that faces the wind, known as the UPWIND SIDE, an unlimited amount of oxygen under high pressure is introduced into the fire.
FF’s should remember to keep the wind at their backs during a fire attack and avoid ventilating on the upwind or downwind side of a fire unless it is part of a well organized suppression effort.
The Impact of Exterior Suppression:
Because of the extremely fuel rich environment found on todays fire ground, ventilation that is not preceded by and concurrent with or immediately followed by effective suppression will introduce enough oxygen to rapidly bring the fire area to flashover TABLE 13-1
Close coordination between the fire attack team and the ventilation crew is required at a fire. Providing ventilation without this coordination can contribute to the growth of the fire and may lead to very dangerous conditions. Figure 13-3
SIZE UP AND VENTILATION:
Location, Size, and Stage of Fire:
The color, location, movement, and amount of smoke can provide valuable clues about the fire’s size, intensity, and fuel. Fig 13-4
- What Is Smoke Inversion aka Cold Smoke?
- The condition in which Smoke hangs low to the ground because of the presence of air. This occurs in buildings with automatic sprinklers, which cools the smoke and produces a cold smoke that may hardly move within the building. It behaves much like fog on a damp day. Mechanical ventilation is often needed to clear this type of smoke form the building.
A similar situation occurs when smoke becomes trapped within a building long enough for it to cool to the ambient temperature.
Types of Construction:
Type 1 (Fire Resistive)
What are four ways a fire can spread in a Fire Resistive Building?
- HVAC Ducts
- Plumbing and electrical chases
- Elevator shafts: Designed with positive pressure to limit smoke migration.
- Stairwells: Also designed with positive pressure to limit smoke migration.
Chase (As in Electrical & Pipe Chase)
Open space within walls for wires and pipes.
What is Vertical Fire Extension AKA Auto Exposure
A fire that spreads from one floor to another through exterior windows
In many of these buildings, engineered designs are installed to assist firefighters with ventilation or controlling the movement of hot gases and smoke throughout the building.
Smoking heat vents are installed in ventilation systems;
Stairwell and elevator shafts are designed with positive pressure to limit smoke migration
HVAC systems are designed to be used by arriving firefighters to pressurize floors or areas to limit fire spread.
In some cases, who is the most valuable person on scene?
The BUILDING ENGINEER, who can assist in the operations of many of the systems from the fire command center.
The roof on a Type 1 building is usually supported by what two materials?
- Concrete
- Steel
Describe the four common descriptions of a Type 2 Construction
Type 2 Construction is most common in what two occupancies?
- Single Story Building with steel frame
- Large Area
- Metal or Concrete Block Walls
- Metal Deck Roof
Warehouses & Factory Buildings
Vertical Spread is not an issue.
Similar to a Type 1 building, Type 2 buildings are most likely going to involve the combustible content of an interior space within the building as the structural components contributed little to no fuel.
Very few windows, so horizontal ventilation is limited on existing doors.
- Vertical ventilation should only be attempted with?
- Aerial Devices
If vertical ventilation is attempted, remember that the building contents may provide a high fuel load, and a fire in this type of building can result in failure of the building walls and collapse of the roof at any time. Additionally, the roof on a type two building is usually supported by metal roof decking. It can be difficult or impossible to make vertical ventilation holes, and these types of roofs.
Ventilation in Type 3 Construction: (Ordinary)
You can use saws and axes to vertically ventilate and horizontally ventilate windows and doors.
Plumbing and Electrical Chases for vertical and horizontal ventilation.
Interior Stairs vertically ventilates.
Be mindful of newer roofs that our new construction over the older roof, making it difficult to vertically ventilate.
Coordinated suppression and vertical ventilation are essential for extinguishing attic or cockloft fires.
Type 4 Construction (Heavy Timber):
- What is type 4 construction exterior walls made up with?
- All interior materials are made of?
- Mansonry Construction
- Heavy Solid Wood
The exterior walls are usually brick and are extra thick to support the weight of the building and its contents.
This type of wood construction is difficult to ignite, but once ignited, it can burn for many hours. The walls soon become unstable and collapse.
They should have no concealed spaces or voids, reducing the risk of horizontal and vertical fire spread that often occurs in ordinary construction buildings. However many type 4 buildings have been converted to small shops, galleries, office buildings, and residential occupancies. This divides up the open space into smaller compartments, creating void spaces. Plus if stairs and elevators are implemented, you will have to treat it like a type 3 construction.
Type 4 usually contains a large number of windows. This type of fire should self ventilate as the windows break from the heat of the fire. Vertical ventilation might be difficult because the size of the thick layers of wood and the building of multiple layers of roofing materials.
Type 5 Construction (Wood Frame):
Has many of the same features as a Type 3 but the exterior is not required to be constructed of masonry or non combustible materials.
Type 5 often contains many voids spaces where fire can spread, including attics and cocklofts.
Modern, fast grown lumber, lightweight wood truss roofs and manufactured I-beam floors, which can fail quickly under fire conditions, which are common in newer buildings.
Older buildings typically use balloon frame construction, which includes vertical channels within the exterior so that fire can spread fast from the basement to the attic or cockloft.
Modern type 5 constructions typically use platform frame construction. In these buildings, the structural frame is built one floor at a time. Between each floor, a plate at the floor and the ceiling acts as a fire stop. Its presence limits the fire from spreading upward and helps contain and limit the fire in a single floor.
Modern type 5 usually uses lightweight components to save money. It contains less wood than solid beams used in older construction. They burn more rapidly and fail much quicker.
Time and Coordination of Ventilation and Suppression:
A vital part of a coordinated fire attack is ventilation. Because it takes time to get a charge hose line in place, opening a vent should sometimes be delayed until the charge hose line is in place and the crew is ready to apply water to the fire from a close and safe location.
When thinking about ventilation, think about the three W’s (When, Where, Why) which include timing.
- To make sure the fire does not get larger, FF’s must first change what?
- Change the fire from a ventilation-limited stage to a fuel limited stage, by applying water. Once the water has begun to cool the fire, more energy is being absorbed by the water than is being general the fire. At this point, the ventilation will begin to work as intended.
Minimizing Backdrafts and Flashovers:
- To prevent a Backdraft or Flashover, what attack should you use?
- A Transitional Attack: Which is an indirect attack from a safe distance, which the water will reduce the heat and fuel in the form of hot gases and smoke from the compartment. Then transition to a direct attack, which reduces the chances of a backdraft or flashover. Fig 13-7
Backdrafts and Ventilation:
- If oxygen is introduced to a ventilated-limited room where there is superheated gases with few flames shown, how fast can it take to ignite and explode?
- What are two ways to eliminate a backdraft?
- The ventilation crew should not ventilate until?
- In cases where flames are beginning to move across the ceiling, a stream of water on the ceiling helps to cool the upper area of the room without upsetting the thermal balance. What is the name of this saying?
- 10 seconds.
- With a transitional attack and vertical ventilation that’s directly on top of the fire. A roof opening can draw gases up and relieve the interior pressure.
- The attack crew is ready to advance with a hoseline.
- “ Cool as you go.”
Flashovers and Ventilation:
- What is a flashover?
- What is the temperature for a flashover to occur?
- In a typical room and contents fire, what temperature can the ceiling reach?
- A transition from a fire that is growing by igniting one type of fuel to another to a fire with all the exposed surfaces have ignited. (Table 13-2)
- 1000 Degrees Fahrenheit
- 2200 Degrees Fahrenheit
TYPES OF VENTILATION:
- There are two basic types of ventilation. What are they?
- Ventilation can either be __ or __?
- Vertical and Horizontal Ventilation.
- Natural or Mechanical.
Natural Ventilation depends on convection or other natural forces, such as the wind, to move heat and smoke out of a building and allow clean air to enter.
Mechanical Ventilation uses fans or other powered equipment to introduce clean air or exhaust heat and smoke.
Horizontal Ventilation:
Wind speed and direction play an important part in natural ventilation. If possible, windows on the down side of a building should be open so that the contaminated atmosphere flows out. Openings on the upwind side can be used to bring in clean air. Conversely, opening a window on the upwind side first could push the fire into uninvolved areas of the structure, particularly on a windy day.
Breaking Glass:
When breaking glass, the firefighter should always use a hand tool and keep in his or her hand above or to the side of the falling glass. This tactic prevents pieces of glass from sliding down the tool and potentially injuring the Fire Fighter. The tool should then be used to clear the entire opening of all remaining pieces of glass, thereby creating the largest opening possible and providing a way for firefighters to enter or exit through the window in the event of an emergency.
Skill Drill 13-1: Breaking Glass with a Hand Tool:
Breaking a Window from a Ladder:
The ladder should be positioned to the upwind side of the window so that Smoke is carried away from the Firefighter. The tip of the ladder should be even with the top of the window. The firefighters should climb to a position level with the window and lock into the ladder for safety. Using a handle, the firefighters should strike and break the window and then clear the opening completely. The firefighters should not be positioned below the window, we could slide down the handle of the tool. (Fig 13-9)
Breaking a Window with a Ladder:
This technique requires proper ladder selection.
- Usually, second- floor windows can be reached by how many feet of a roof ladder?
- How many ft for bedded ladders?
Answer 1: 16-20ft roof ladders
Answer 2: 24 bedded or 28 ft extension ladders
Skill Drill 13-2: Breaking Windows with a Ladder:
What is Bidirectional Flow?
Clean air entering through the bottom half of the exterior door and smoke escaping through the top half.
Negative-Pressure Ventilation:
The basic principals of airflow are used in negative pressure ventilation. Firefighters locate the source of the fire, and using a smoke ejector, exhaust the products of combustion out through a window or door. The Smoke ejector creates a negative pressure that draws the heat, smoke, and fire gases out of the building. In turn, fresh air into the structure, to replace the exhaust contaminated air.
Airflow control with a negative pressure system is difficult. The smoke ejector must be completely sealed so that the exhausted air is not immediately drawn back into the building. This phenomenon, which is called recirculation, reduces the effectiveness of the smoky projector. Recirculation can be eliminated by completely blocking the opening around the ejector.
Skill Drill 13-3: Delivering Negative-Pressure Ventilation:
Positive Pressure Ventilation:
- What is Positive Ventilation?
When using positive pressure ventilation, it is necessary to provide an outlet or exhaust opening such as an open window or door, to release the positive pressure created by the fan. This opening must be located in the fire room to effectively allow the heat and smoke to escape.
- Used to force fresh air into a structure. The fan creates a positive pressure inside the structure, which displaces the contaminated atmosphere and pushes heat and other products of combustion out.
When using positive pressure ventilation, it is necessary to provide an outlet or exhaust opening such as an open window or door, to release the positive pressure created by the fan. This opening must be located in the fire room to effectively allow the heat and smoke to escape. Fig. 13-12.
The size of the exhaust opening should be a two to one ratio to the entry opening to create the desired positive pressure within the room. It is also important that the interior door of the fire room and not the exterior door of the structure dictate the size of the exhaust opening. a higher pressure must be maintained at this opening in order to retain an efficient flow if there is no exhaust or if the opening is too small located and other areas of the structure, the heat and smoke can flow into the other areas of the building or back toward the attack team. In addition, this kind of system will not work effectively if the building is not intact.
- To increase the efficiency of positive pressure attack, or ventilation to prevent smoke and fire from reaching other parts of the building, what should firefighters do?
- Close doors to unaffected areas of the structure. This is an effective action to maintain the tenable environment for people trapped in other parts of the building.
When planning positive pressure attack or ventilation, the force and direction of the wind need to be taken into consideration. Positive Pressure fans should never be placed in a position where they are blowing against the wind. Check the direction to speed of the wind before placing fans, and monitoring the wind for changes and direction or intensity.
Recent studies have demonstrated that opening all windows immediately after fire suppression operations is most effective when in ventilating a single family or two family residence. Note, this recommendation only applies to positive pressure ventilation after the fire has been extinguished. During positive pressure attack, on the other hand, only openings in the fire room have been proven to be effective. Openings other than those in the fire room permit the fire to propagate to other areas of the structure. In a high-rise building, positive pressure fans can blow fresh air up through a stair shaft. By opening the doors, firefighters can clear one floor at a time. Very large structures can be ventilated by placing multiple fan side-by-side.
Advantages of Positive Pressure ventilation is:
- Easy to set up and with just one man.
- Because the fan is positioned outside, it doesn’t interfere with interior operations.
Disadvantages:
1. Improper use of it can spread a fire into other areas. If the fire is located in structural void spaces, it should not be used until access to these spaces is available and attack crews are in place. Ineffective positive pressure ventilation occurs if positive pressure is used and there are no openings for exhaust gases to release the positive pressure from the building.
Most positive pressure fans are powered by internal combustion engines, so they can increase carbon monoxide levels if they are ran for significant periods of time after the structure is cleared to prevent carbon monoxide build up.
Skill Drill 13-4
Hydraulic Ventilation:
Hydraulic Ventilation uses the water stream from the hose line to exhaust smoke and heated gases from a structure. The FF directs a narrow fog stream or a broken pattern stream from a fog stream nozzle out of the building through an opening, such as a window or doorway. The contaminated atmosphere is drawn into a low pressure area behind the nozzle. An induced draft created by the high pressure stream of water then pulls the smoke and gas out through the opening. Fig 13-13.
Skill Drill 13-5: Delivering Hydraulic Ventilation
Vertical Ventilation:
Vertical Ventilation should be made as close as possible to the seat of the fire. Smoke issuing from the roof area, melted asphalt shingles, or steam coming from the roof surface are all signs that FF can use to identify the hottest point.
Safety Considerations in Vertical Ventilation:
Determine the type of roof construction before beginning roof ventilation. If the roof is co stricter with lightweight trusses, ventilate the roof from an aerial device. Fig. 13-4
If FF’s must cut through a roof to create a hole, the location should be identified and the operation should be performed promptly and efficiently. It must be done in coordination with the other FF’s operating on the fire scene.
FF working on the roof should always have two safe exit routes. A second ground ladder or aerial device should be positioned to provide an alternative exit. They should be separate from each other and preferably in the opposite direction from the operation site.
The ventilations should never be located between the FF’s and their exit routes.
Once a ventilation hole has been made, FF should immediately withdraw to a safe location.
FF operating on a roof should not be a standard practice and should be done if it’s absolutely necessary.
Roof Ops should be done on an aerial or a roof ladder, especially with a pitch roof.
⭐️ On roofs, FF’s should follow the areas of the greatest support and strength, which is the roof edges, which are supported by bearing walls and the hips and valleys of the roof, where structural materials are doubled in strength vs. interior sections of the roof.
⭐️FF should be upwind, have two exit routes, and stand on a firm section of a roof or on an aerial or roof ladder.
If FF are upwind from the hole, the wind will push the heat and smoke away from them; thus escaping heat and smoke should not block the exit route.
Roof Construction:
- Roofs have 3 major components. What are they?
- The Support System can be constructed of solid beams of what four materials?
- What is Roof Decking? What three things are they composed of?
- What is a Roof Covering?
- • The Supporting Structure
• Roof Decking
• Roof Covering - • Wood
• Steel
• Concrete
• Lightweight Construction - The portion of roof between the roof supports and the roof covering. It is composed of Wooden Boards, Plywood Sheets, or Metal Panels.
- It’s applied to the top of the decking and can have several layers and constitutes the weather resistant surface of the roof.
- What are the two major structural support systems for roofs?
- What is the basic difference between Solid-beam and Lightweight construction?
- Solid Beam and Lightweight Construction
- The way individual load-bearing components are made. Solid beam construction uses solid components, such as girders, beams, and rafters to support the roof, while Lightweight Construction is assembled from smaller, individual components and includes trusses or engineered systems such as I-joist.
Rafters are made by 2x8 2x10 and 2x12
- What are Trusses?
- Lightweight construction used for roof support are often what size?
- What is a Gusset Plate?
- Trusses also may be made of individual steel bars or angle sections that are welded together. What are light weight steel trusses alternative name?
Lightweight construction can be found in almost any type of roof or floor, Including flat roofs, pitched roofs, Or curved roofs. Firefighters should assume that any modern construction uses lightweight construction for the roof support system until proven otherwise.
- Constructed by small and lightweight components of wood, steel or a combination of both in a series of triangles
- 2 inches by 4 inches.
- Connecting plates made of a thin sheet of steel.
- Bar Joist. Bar joist often support flat roofs on commercial or industrial buildings. Horizontal cracks in the upper part of the wall may indicate that the steel roof supports are pushing outward. (Pic is at the end).
Roof Design:
- There are 3 main roof designs. What are they?
Flat Roofs can have Parapet Walls.
Pitch roofs are usually supported by trusses or rafters. The rafters usually run from one load bearing wall up to a center ridge pole and back to another load bearing wall.
- What is Laths?
- Flat Roof, Pitched Roof, and Curved Roof.
- Laths are thin parallel strips of wood, instead of solid sheeting to support the out covering (view picture).
Curved roofs are generally found in commercial structures because they create large open spans without requiring the use of columns. This type of roof is common in supermarkets, warehouses, industrial buildings, arenas, auditoriums, bowling alley’s, churches, air planes hangars and other Similiar buildings. Fig 13-21
Steel or bowstring trusses or arches usually are used to support curved roofs. These trusses are usually spaced 6 to 20ft apart and are what give the roof its distinctive curved shape.
Although these roofs are quite distinctive when seen From above or outside, their structure might not be evident from inside the building because a flat ceiling is attached to the bottom cords of the trusses. This creates a huge attic space that is often used for storage. A hidden fire within the space can severely and quickly we can do bowstring trusses. The collapse of a bowstring truss is usually very sudden.
Vertical Ventilation Techniques:
- Before starting any vertical ventilation operation, firefighters must make an initial assessment. What are the 5 things FF should note?
- Examination openings can be used to determine how large an area is involved, whether a fire is spreading and in which direction it is moving. There are two types of examination cuts. What are they? Fig 13-22
- • Construction Features
• Indications of possible fire damage.
• Establish Safety Zones
•. Establish 2 exit paths
•. Identify natural ventilation on the roof - • Kerf Cut
• Triangle cut
- What’s a Kerf Cut?
Once the optimal place to vent is located, the ventilation team should determine the most appropriate type of opening to make. Built-in rooftop openings provide readily available ventilation openings.
Cutting one large hole is better than cutting several small holes.
Some departments recommend starting with a 4X4 Square hole. Fig 13-24
- A single slit cut into the roof with a power saw for an examination.
Skill Drill 13-6: Operating a Power Saw on a roof Ladder
Skill Drill 13-6 Continued
Skill Drill 13-7: Making a Rectangular or Square Cut:
Making a square cut or any cut, you cut parallel first and away from you, then you cut the two perpendicular cuts and the last cut will be parallel but close to you. This is to avoid a fall.
7,8,9, Rectangular Cut:
This cut is for larger commercial buildings requiring larger ventilation openings. If it is a flat roof, 7,8,9 Rectangular cut is an effective ventilation technique.
Skill Drill 13-7: Making a Rectangular or Square Cut:
Making a square cut or any cut, you cut parallel to the roof supports, first and away from you, then you cut the two perpendicular cuts and the last cut will be parallel but close to you. This is to avoid a fall.
7,8,9, Rectangular Cut:
This cut is for larger commercial buildings requiring larger ventilation openings. If it is a flat roof, 7,8,9 Rectangular cut is an effective ventilation technique. There are 7 cuts that needs to be made, resulting in a 4X8ft ventilation hole.
Skill Drill 13-8: Making a 7,9,8 Rectangular Cut:
Skill Drill 13-9: Making a Louver Cut
This is why they call it a Louver cut (See Pick)
Skill Drill 13-10: Making a Triangle Cut
Skill Drill 13-11: Making a Peak Cut
Skill Drill 13-12: Making a Trench Cut
Ventilating Basements:
The traditional tactic of applying water down the interior stairway, while advancing into the seat of the fire should no longer be considered the safe operation. A straight or solid stream of water applied through an external window or external door quickly darkens the fire and reduce temperatures throughout the building. Figure 13–25. This technique did not push fire or hot gases up the interior stairs. The cooling effect lasted for several minutes before the fire grew back to the size it was before the application of the water. Table 13-3.
When attacking basement fires, the use of interior stairs for ventilation should not be considered a safe option because of the potential for failure of the floor system, and the danger of firefighters being in the exhaust flow path of hot gas is from the fire.
Ventilating High-Rise Buildings:
Ventilating a high-rise building can be challenging. Most high-rise buildings have sealed windows that are difficult to break. In addition, high-rise buildings have unique patterns of smoke movement, such as smoke might be trapped on individual floors, or it may move up or down within the vertical shafts.
Many new high-rise buildings have incorporated Smoke management capabilities into their HVAC systems. Use of this type of system enables different areas to be pressurized with fresh air and contaminated air to be exhausted directly to the outside. If the HVAC system does not have this capacity, it can complicate problems by circulating smoke to different areas of the building.
- What is a Stack Effect?
- What is a Reverse Stack Effect?
- The stack effect is a response to the differences and temperature inside and outside the building. A cold outer atmosphere and a heated interior call Smoke to rise quickly through stairways, elevator shafts, and other vertical openings, filling the upper levels of the building. Fig 13–26.
- The stack effect is a response to the differences and temperature inside and outside the building. A hot summer day when the interior temperature is much cooler than the outside atmosphere. In this scenario, the heavy cooler air pushes the smoke down the vertical openings, toward the lower level exit. Fig 13-27
After the smoke mixes with fresh air or is hit by water from sprinklers or hose streams, it cools and can sit in one location. Can fill several floors and usually needs to be cleared by mechanical means. A key objective and ventilating a high-rise building is to manage the air movement in stairways in elevator shafts. Positive pressure ventilation can help keep stairways clear and ventilate individual floors and high-rise buildings.
At least one stairwell should be designated as the evacuation stairwell and announce to the operating companies. This stairwell should be kept well ventilated and as an occupant and rescue route. Some newer buildings have smoke proof, stair towers, or pressurize stair shafts that are designed to keep smoke out of the stairway. Otherwise, positive pressure fans can be used in the stairway to keep out smoke. Place the positive pressure fans at a ground floor doorway positioning them, so that fresh air blows into the stairway. A pressurized stairway also can be used to clear smoke from the floor. Opening a door from a stairway allows fresh air to enter the floor. The contaminated atmosphere can then be vented out through a window or another stairway.
Ventilating Windowless Buildings:
- Many structures do not have buildings. Fog 13-28. These type of buildings pose two significant risk to FF. What are they?
Windowless buildings are Similiar to basement in terms of ventilation approach to be used. Any ventilation needs to be as high as possible, and probably requires mechanic assistance. Using existing rooftop openings, cutting openings in the roof, reopen, boarded up windows or doors, and making new openings and exterior walls are all possible ways to ventilate windowless structures.
- Heat and products of combustion trapped/ N FF have no second exit route.
After-Action Review
Definitions
Trusses made of steel bars and called what?
Bar Joist
