Collapse of BB CH9 Easy

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Questions and Answers

What is the size of the apartment building?

50x75 feet

What obstructs the advance of the first attack hoseline?

Extreme heat and flames

What does the chief order the captain of Ladder 6 to do?

Vent the top floor

What type of roof construction is far superior in terms of withstanding higher temperatures for longer periods before it fails?

Wood joist system Signup and view all the answers

In brick cavity construction, where are the solid wood beams placed?

Within a recessed portion of a brick wall and cemented into position Signup and view all the answers

What does a restrained beam mean in the context of roof stability?

It is rigidly held in position at both ends in a brick cavity Signup and view all the answers

In corbel shelf construction, where do the wood joists rest?

On a girder or brick corbel shelf Signup and view all the answers

What does an unrestrained beam mean in the context of roof stability?

It has ends resting on a girder or brick corbel shelf Signup and view all the answers

What type of roof construction poses increased risks to firefighters compared to conventional solid wood beam roofs?

Modern lightweight roof construction Signup and view all the answers

Size-up of a fire below is difficult because a watertight, wooden roof deck, covered with many layers of paper and tar,

acts as insulation, concealing the heat of the fire and roof instability Signup and view all the answers

What is highlighted as a necessity during fires but poses challenges in evaluating roof stability?

Roof venting operations Signup and view all the answers

What type of construction did the World Trade Center building have that posed increased risks to firefighters?

Lightweight construction with long-span steel bar joists Signup and view all the answers

What should firefighters be trained in for operating in buildings with lightweight roof construction?

Defensive strategies Signup and view all the answers

What is emphasized as important for evaluating a roof's stability during firefighting operations?

Knowledge of the support system and connection method Signup and view all the answers

What poses hazards to firefighters when completing a roof and top floor venting assignment in a burning building?

Potential roof collapses and sudden explosion of flame Signup and view all the answers

What does the National Fire Protection Association's study show about firefighter fatalities related to roof collapses?

19 out of 56 firefighters were killed by roof collapses Signup and view all the answers

What should be conducted for new construction to ensure firefighter safety according to the text?

Pre-fire plan inspections Signup and view all the answers

What type of information may not always be readily available during firefighting operations according to the text?

Information about the support system and connection method Signup and view all the answers

What is the main objective of the firefighters on the roof of the building?

To cut vent holes and release smoke and heat from a fire inside Signup and view all the answers

What challenges do the firefighters face while working on the roof?

Maintaining stability in a smoky and windy environment Signup and view all the answers

Who is responsible for ensuring safety during the roof ventilation operation?

The captain Signup and view all the answers

What tool do the firefighters use to cut vent holes in the roof?

Power saws Signup and view all the answers

What does the observation of flames and smoke coming out of the vent openings indicate?

Effectiveness of the ventilation operation Signup and view all the answers

What does the captain notice about the hose team below during the operation?

Lack of water stream, indicating a potential problem in the firefighting operation Signup and view all the answers

What are steel bar joists?

Metal trusses used to support roof decks in commercial structures Signup and view all the answers

What is a steel bar joist roof system composed of?

Fluted metal steel decking, insulation, and a fire-retarding layer Signup and view all the answers

What can cause the rapid collapse of a steel bar joist roof system during a fire?

Heating of the steel bar joists Signup and view all the answers

What did NIST state about determining the necessary thickness of spray-on material for fire protection?

There is no scientific basis for deciding the necessary thickness Signup and view all the answers

Why is early identification of truss construction by firefighters crucial?

For safe fire operations in buildings with steel or wood trusses Signup and view all the answers

What type of occupancy can cause rapid failure of steel truss roof construction?

High hazard occupancy such as storage of flammable materials Signup and view all the answers

What type of ventilation is preferred when dealing with a fire building having a steel bar joist system supporting the roof?

Horizontal ventilation of windows and doors Signup and view all the answers

What can cause lightweight wood truss construction to fail within 5 to 10 minutes of fire exposure?

Fire exposure Signup and view all the answers

What provides greater stability to a roof during a fire than its lightweight counterparts?

Conventional solid wooden joist Signup and view all the answers

What can a firefighter do on a fire-weakened conventional wooden joist roof that they cannot do on many lightweight roof supports?

Grab onto a beam and avoid falling into the fire below Signup and view all the answers

What do steel bar joist roof systems and lightweight wood truss construction pose according to the text?

Significant fire safety concerns Signup and view all the answers

What can cause a collapse hazard on a roof when a temporary repair is made?

Laying a thin layer of roofing paper over an opening without replacing the roof decking or beams Signup and view all the answers

What is the danger presented by the common scuttle cover on a roof?

It is not designed to support the weight of a firefighter Signup and view all the answers

What should firefighters be cautious about when encountering a freshly repaired roof section?

Avoid walking on any repaired sections, particularly in partly vacant buildings or those that have experienced a previous fire Signup and view all the answers

What can happen if supporting beams are absent or widely spaced in lightweight constructed roofs?

The firefighter could fall through to the floor below Signup and view all the answers

What may a scuttle cover actually be in some cases?

A covered-over skylight opening Signup and view all the answers

What should a disoriented firefighter do when on a roof during a fire?

Get down on hands and knees and crawl Signup and view all the answers

What is the recommended last line of defense for a trapped firefighter in a fiery environment?

Helmet, gloves, hood, bunker type turnout gear, and an operable self-contained-breathing apparatus Signup and view all the answers

What should a firefighter do if smoke or darkness momentarily blinds them and there is no immediate danger?

Remain in place until the wind changes and the smoke clears Signup and view all the answers

What should a disoriented firefighter use to feel for the presence of the roof deck and its stability before moving forward?

A tool or an outstretched leg Signup and view all the answers

What can happen if a firefighter attempts to quickly evacuate the roof at the rear by scaling the parapet wall without noticing the shaft?

They will fall into the shaft Signup and view all the answers

Study Notes

Steel Bar Joist Roof Systems and Fire Safety Concerns

Steel bar joists are metal trusses used to support roof decks in commercial structures, replacing wooden joists in new and renovated buildings in the United States.
A steel bar joist roof system typically consists of fluted metal steel decking, insulation, and a fire-retarding layer, with options for additional fire protection such as spray-on insulation or a membrane panel ceiling.
If the fire penetrates the fire-resistant ceiling and heats the steel bar joists, the roof can collapse rapidly, as exposed steel joist systems may collapse after only five or ten minutes of exposure to fire.
NIST stated that there is no scientific basis for deciding the necessary thickness of spray-on material required to fire protect open web steel joists for one or two hours of fire resistance, leading to guesswork in the construction industry.
Steel bar joist trusses in one-story commercial buildings, especially strip stores, are often concealed from the exterior and the roof, making it challenging for firefighters to identify this type of roof support system.
Early identification of truss construction by firefighters is crucial for safe fire operations in buildings with steel or wood trusses.
Noncombustible construction using steel bar joists is designed for low hazard occupancy, but if the occupancy changes to high hazard, such as storage of flammable materials, the steel truss roof construction can fail rapidly.
When a fire building has a steel bar joist system supporting the roof, horizontal ventilation of windows and doors is preferred to vertical ventilation, which requires firefighters to operate on the roof above the fire.
Lightweight wood truss construction, widely used in private dwellings and stores, can fail within 5 to 10 minutes of fire exposure, contributing to firefighter deaths.
The conventional solid wooden joist provides greater stability to a roof during a fire than its lightweight counterparts, giving warning signs before collapse due to its wooden roof deck and closely spaced joist system.
A firefighter walking on a fire-weakened roof deck of a conventional wooden joist roof can grab onto a beam and avoid falling into the fire below, which is not the case with many of the new lightweight roof supports.
Steel bar joist roof systems and lightweight wood truss construction pose significant fire safety concerns, requiring early identification, proper fire protection, and careful consideration of occupancy hazards.

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