Ch9 pg 257-261

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Questions and Answers

What is the primary architectural feature of H-type buildings that contributes to fire spread?

Wider connecting sections

A common cockloft (correct)

Separate stairwells

Individual balconies

Which shape is NOT typically associated with H-type buildings?

T (correct)

What term describes the narrow section connecting adjacent areas in H-type buildings?

Connector

Chamber

Passageway

Throat (correct)

What is a significant risk firefighters face when combating fires in H-type buildings?

Fire in the cockloft space Signup and view all the answers

During a fire in an H-type building, what is the usual response of firefighters in one wing experiencing a large body of fire?

Retreat and prevent spread to other wings Signup and view all the answers

What is the primary purpose of a trench cut?

To create a firebreak Signup and view all the answers

During which decades did fire activity in New York City significantly increase?

1960s and 1970s Signup and view all the answers

What type of buildings were involved in the increased fire activity in New York City?

Large, multiwinged apartments called H types Signup and view all the answers

What does a trench cut specifically target in terms of roof modifications?

Creating a firebreak Signup and view all the answers

Which of the following is not a reason for the use of trench cuts?

To improve aesthetic appearance Signup and view all the answers

What must be completed before beginning the operation of making a trench cut?

Main ventilation hole Signup and view all the answers

Which of the following is NOT one of the steps in making a trench cut?

Filling the trench Signup and view all the answers

In larger departments with available equipment, how many saws are suggested to begin cutting the trench while others handle ventilation?

Two saws Signup and view all the answers

What is the purpose of cutting inspection holes during the trench cutting process?

Twofold-ensure fire hasn’t passed the trench and to serve as indicators of when to begin pulling Signup and view all the answers

Which option best describes what should happen in departments with fewer than four saws?

Trench cutting should not begin Signup and view all the answers

What is the primary reason for locating the trench close to the fire?

To limit unnecessary extension Signup and view all the answers

How far from the main vent hole should the trench be located?

20-25 ft Signup and view all the answers

What is crucial to complete before the fire passes the trench location?

Cutting and pulling Signup and view all the answers

What assumption is made regarding the main body of fire in relation to the trench?

It is below the main vent hole Signup and view all the answers

What could happen if the trench is located too close to the fire?

There would not be enough time for all tasks Signup and view all the answers

What is the main purpose of making inspection holes before cutting a roof trench?

To check for the presence of fire and guide the trench cutting process. Signup and view all the answers

How far in front of the intended edge of the trench should inspection holes be made?

5 to 6 ft Signup and view all the answers

What is the minimum allowable width for a trench to prevent fire from jumping past it?

3 ft Signup and view all the answers

What should be ensured by making additional examination holes on the safe side of the trench?

That no fire gets past the trench. Signup and view all the answers

Which of the following describes the correct method for cutting the trench?

Make two parallel cuts about 3 ft apart from outer wall to outer wall. Signup and view all the answers

What should be considered when locating the fire trench in a building?

The construction features of the building to minimize cutting Signup and view all the answers

What is the primary reason for positioning the trench at the narrowest point?

To minimize the area of fire spread Signup and view all the answers

What should firefighters utilize when fire partitions do not extend through the roof?

Fire barriers and trench technique Signup and view all the answers

How does wind influence the direction of fire spread?

Fire usually travels towards the downwind side Signup and view all the answers

In the absence of wind, what factor becomes significant for fire spread on a roof?

The pitch of the roof Signup and view all the answers

What is the primary purpose of creating knockouts on the fire side of the trench?

To provide access for tools to grab roofing Signup and view all the answers

How should cuts be made for the trench?

Parallel and near the outer walls Signup and view all the answers

What should be considered when positioning hoselines?

There should be one hoseline per room below the trench Signup and view all the answers

What is a critical safety measure for personnel on the fire side of the trench?

They must have at least two ways off the roof Signup and view all the answers

Why is pushing down on ceilings more effective than pulling them down?

Members on the roof know the trench's location Signup and view all the answers

What is the maximum distance between handlines that should be positioned on the roof for trench cuts?

15-20 ft Signup and view all the answers

In which type of building are trench cuts particularly effective?

H-type buildings Signup and view all the answers

Why do large-area structures like supermarkets not typically benefit from trench cuts?

The length of cuts needed is impractical. Signup and view all the answers

What alternative method is suggested for fighting fires in large-area buildings with existing fire in the cockloft?

Cutting vent holes over the fire. Signup and view all the answers

How many parallel cuts are needed for a 75-ft deep store to create a trench?

Two Signup and view all the answers

What is the most logical place to cut off an extending fire?

In the throat area Signup and view all the answers

Why is the narrowness of the throat area advantageous in a fire situation?

It minimizes the risk of being outflanked by fire. Signup and view all the answers

What technique was developed to cut parallel vent holes quickly?

The trench cut Signup and view all the answers

What is a significant benefit of having an open courtyard next to the throat area?

It ensures fire cannot get behind the personnel. Signup and view all the answers

What realization helped fire personnel improve their cutting strategy on roofs?

Two parallel cuts can be made faster than several smaller vent holes. Signup and view all the answers

What should the roof team wait for before pulling the trench open?

Fire shows at the examination holes on the fire side Signup and view all the answers

What is the consequence of pulling the trench open immediately?

It can draw fire towards fresh air Signup and view all the answers

What must be done to materials below the trench before pulling it?

They must be completely removed Signup and view all the answers

How should members assist with the ceilings below the trench?

By pushing them down if not fully pulled Signup and view all the answers

What is the primary goal of cutting the trench?

To contain and control the fire Signup and view all the answers

Study Notes

Trench Cuts Overview

Trench cuts create firebreaks along the roof’s surface to combat spreading fires.
The technique gained prominence in New York City during the 1960s and 1970s due to increased fire incidents.

H-Type Buildings Characteristics

H-type buildings have a distinctive H, E, or O shape and feature common cocklofts above all wings.
The throat, a narrow connecting section, joins adjacent large areas and is critical for fire control.
Major risks arise from fires in the cockloft, which can propagate through the entire structure.
Firefighters often need to retreat when facing large fires and can strategically combat extensions at the throat area.

Trench Cut Process

Successful trench cutting follows a methodical sequence: locating, cutting inspection holes, cutting the trench, and pulling the trench.
Operations should not commence until the main ventilation hole is established, except in large departments with multiple saws available.
Trench location must balance proximity to the fire for efficiency and distance to safely complete operations.

Locating the Trench

The trench should be situated close enough to limit fire extension but far enough to allow time for cutting and pulling (approximately 20-25 ft from the main vent hole).
Utilize building construction, such as narrow points, skylights, or stair bulkheads, to minimize cutting.
Fire partitions not extending through the roof can slow fire progression; these areas are also useful for trench placement.

Inspection Holes Importance

Create inspection holes 5-6 ft in front of the intended trench edge for fire assessment and to time trench pulling.
Additional holes on the safe side verify no fire has passed through.

Cutting the Trench

Make two parallel cuts approximately 3 ft apart from wall to wall, avoiding cuts narrower than 3 ft to prevent fire jumping.
Wider cuts take longer; keep subsequent cuts parallel and as close to outer walls as possible to divide the trench into smaller sections.

Fire Officer's Safety Protocols

Ensure personnel have multiple escape routes from the roof, maintaining safety during extreme conditions.
Use hoselines effectively on the top floor and safe side of the trench for protection and fire control.

Post-Cutting Procedure

Pulling the trench should be carefully timed; wait for signs of fire through inspection holes before opening it.
Remove all materials below that could assist fire spread and push down ceilings when necessary.

Suitability of Trench Cuts

Trench cuts are ideal for H-type buildings and long narrow garden apartments but less effective in larger structures like supermarkets due to impractical cutting requirements.
For large-area fires in cocklofts, multiple large vent holes are often a more suitable strategy than trench cuts.

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Description

Test your knowledge on trench cuts and their application in H-type buildings. This quiz covers the characteristics of H-type structures, trench cutting techniques, and the importance of fire control methods. Understand how these elements work together to enhance firefighting strategies.