IFSTA CH 11 Ventilation

Question 1

Tactical Ventilation

Answer 1

the planned and systematic 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

Question 2

reasons for tactical ventilation

Answer 2

It is a tool to help firefighters control a fire

Also used during overhaul and loss control to evacuate smoke from structures after the fire has been extinguished

Being in control of the fire means using ventilation and water application to control its behaviour

An effective way of controlling ventilation is to cover openings rather than creating more openings

Question 3

Controlling Oxygen Availability

Answer 3

As the oxygen inside the room or structure gets consumed, the fire burns less efficiently and the amount of unburned fuel in the combustion products increases

If the compartment or structure does not ventilate before consuming most of the available oxygen, the fire enters a state of ventilation-limited decay

Question 4

Tactical ventilation that is implemented during or after suppression can create an interior environment or egress path with the following, more tenable conditions:

Answer 4

Increased oxygen concentration

Reduced concentration of toxic products of combustion

Reduced temperature levels

Increased visibility to aid in fire fighting operations and primary search operations

Question 5

SAFETY CONSIDERATIONS WHEN VENTILATING

Answer 5

Careful planning

Communication of scene observations to the IC

Systematic application of procedures for removing the contaminants

Coordination with other fireground activities

Recognition that all openings are ventilation

Recognition of the advantages and disadvantages of environmental conditions at the scene

Question 6

Wind Conditions

Answer 6

Winds as slow as 10mph can affect structure fires, potentially making them wind-driven

If winds are at these speeds or faster, firefighters are safest working with the wind at their backs

Question 7

Elements that may contribute to roof failure during a fire

Answer 7

Lightweight roof trusses

Open floor plans under wide expanses with limited truss supports

Prior structural damage to the roof

Question 8

Indications of possible roof collapse

Answer 8

Melting asphalt

Smoke coming from the roof

Fire coming from the roof

Building systems such as HVAC units sagging or leaning

Spongy roof

Question 9

natural ventilation

Answer 9

Involves opening doors and windows to allow air currents and pressure differences to remove smoke and heat from the building

door control is another form of natural ventilation

Question 10

mechanical ventilation

Answer 10

Involves the use of fans and ejectors to create pressure differences

Question 11

hydraulic ventilation

Answer 11

Uses water streams to ventilate compartments and create pressure differences

Question 12

Wind Assisted Ventilation

Answer 12

When the IC gives the order, windows and doors on the downwind side of the structure should be opened first to create an exhaust point. Openings on the upwind side of the structure are then opened to permit fresh air to enter forcing the smoke toward the exhaust openings

Question 13

Creating negative pressure

Answer 13

Means artificially lowering the pressure inside the structure so that fresh air from outside moves in more quickly

Question 14

creating positive pressure

Answer 14

Artificially raising the pressure inside the structure so that smoke and fuel gases move toward lower-pressure openings more quickly

Question 15

Mechanical Horizontal Ventilation Before and During Fire Suppression

Answer 15

Accelerates the exchange of fresh air into a structure filled with smoke and hot gases

Question 16

Some limitations of mechanical ventilation include the following:

Answer 16

Depends upon a power source

Requires special equipment

Requires more resources and personnel than natural ventilation

Question 17

Mechanical Horizontal Ventilation uses after Fire Suppression

Answer 17

Clearing contaminated structures of smoke reduces smoke damage and improves relations with home or business owners

Question 18

Some advantages of using mechanical ventilation to clear contaminated atmosphere are:

Answer 18

Supplement and enhances natural ventilation

Ensures more control of air flow

Speeds the removal of contaminants

Reduces smoke damage

Promotes good public relations

Question 19

Negative-Pressure Ventilation (NPV)

Answer 19

Air movement equipment is used to develop artificial air flow to pull smoke from the structure or to enhance natural ventilation

Requires electricity, generally supplied by a cord run from a generator to the fan

Requires that the opening around the fan be sealed to prevent outside air from being drawn in around the fan

Question 20

Positive-Pressure Attack

Answer 20

The intent is to use high-volume fans to create a slightly higher pressure in adjacent compartments and force the products of combustion (smoke) to the exterior of the structure through exhaust openings that either exist or have been created

Question 21

intake

Answer 21

Opening where the fan is set up and air flow is introduced

Question 22

exhaust

Answer 22

Location where the intended products of combustion will be exhausted from the structure

Question 23

two main considerations for PPA

Answer 23

fire location

exhaust-to-intake size ratio

Question 24

Hydraulic Ventilation

Answer 24

May be used in situations where other types of forced ventilation are unavailable

Can be used to clear a room or building of smoke, heat, steam and gases after a fire has been controlled

Uses a spray stream from a fog nozzle to entrain smoke and gases and carry them out of the structure through a door or window

Requires firefighters to operate the nozzle within the contaminated atmosphere

Question 25

Hydraulic Ventilation disadvantages

Answer 25

water damages may increase within the structure

depletes the water supply, a more common problem during rural fire fighting operations where water shuttles are being used

more ice will form on the ground surrounding the building when temperatures are below freezing

the firefighters operating the nozzle must remain in the heated, hazardous atmosphere throughout the operation

Question 26

VERTICAL VENTILATION

Answer 26

involves creating openings in a roof or using existing openings to channel smoke, hot gases and products of combustion out of the structure

for vertical ventilation to be effective, a horizontal inlet opening at or below the level of the fire is needed to provide a flow path for fresh air to enter the structure

Question 27

sounding the roof

Answer 27

striking the surface of a roof to determine its structural integrity

provides no information about the structural members beneath the sheathing, sheathing may sound solid but will fail under your weight

Question 28

inspection holes

Answer 28

help to determine the location of a fire, the presence of fire below the roof and construction features of the roof

comparing observations from multiple inspection holes can provide information about the fire spread

Question 29

two primary types of inspection holes

Answer 29

kerf cut
triangle cut

Question 30

kerf cut

Answer 30

easiest and fastest inspection hole to cut

make a single cut in the roof surface using a rotary saw, chain saw or axe

Question 31

triangle cut

Answer 31

may provide a better view of conditions beneath the roof

Question 32

Ventilating Flat Roofs

Answer 32

square or rectangular openings are the most common types made in a flat roof

these openings can be made between the roof trusses or with the truss in the middle of the opening

when the truss is in the middle of the opening a louver cut is used

Question 33

Ventilating Shingle-covered Pitched Roofs

Answer 33

cut a few inches below the peak on the downwind side

always cut exhaust openings at or very near the highest point on the roof when possible

Question 34

Ventilating Slate or Tile-Covered Pitched Roofs

Answer 34

can be sliced open with an axe, carbide tip chain saw or rotary saw and peeled back

Question 35

Creating Trench Cuts

Answer 35

the purpose of trench cuts is to create a defensible line ahead of the fires spread

are created ahead of the advancing fire: how far ahead is based upon the fires rate of growth

generally the distance is far enough to ensure that the fire will not reach the personnel creating the cut before they have finished their work

Question 36

trench cut is created in two steps

Answer 36

make two parallel cuts that extend form one exterior wall to the opposite exterior wall

remove the roof material between the cuts and push down the ceiling material below

trench cut should be 4 or more feet wide and extend the width of the building

Question 37

advantages of trench cuts

Answer 37

can be used to establish a defensive position in the attic space for fire attack among structures with a common attic

works well in large buildings

Question 38

disadvantages of trench cuts

Answer 38

can be time-consuming or physically taxing on personnel

can place firefighters in the dangerous position of working ahead of the fire

if it is created improperly or at the wrong time, it can cause the fire to spread more rapidly and potentially destroy the structure

Question 39

Methods for Ventilation Basements

Answer 39

if the basement has ground level windows or even below ground level windows in wells, horizontal ventilation can be employed effectively

Question 40

High-Rise Fires

Answer 40

fire, smoke and toxic gases can spread rapidly through pipe chases (shafts), stairways, elevator shafts, unprotected ducts and other vertical and horizontal openings in high-rises

these openings contribute to a stack effect* creating an upward draft and interfering with evacuation and ventilation

horizontal smoke spread* and hot gas layer development can also occur when an exhaust opening does not match the fire size