Chapter 6

Question 1

During fires within a compartment, the characteristics of the initial fuel package, as well as all other fuels present, will influence the rate of fire spread and growth within the space.

Answer 1

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Question 2

During the development of an incipient fire, the rate of flame spread, and heat release rate is greatly dependent on the configuration and characteristics of the fuels involved.

Answer 2

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Question 3

As radiant heat from the fire warms nearby fuels, it continues the progress of further pyrolysis allowing the flames to continue to spread and involve more fuel surfaces causing the fire’s HRR to increase as the fire moves into the growth stage.

Answer 3

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Question 4

When the plume reaches the ceiling, the flow is diverted horizontally under the ceiling as a ceiling het and flows in all directions until the gases strike the wall of the compartment.

Answer 4

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Question 5

The height at which the flow changes direction is known as the neutral plane.

Answer 5

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Question 6

As the fire continues to grow, the ceiling layer gas temperature and the intensity of the radiation on the exposed combustible contents in the room increases.

Answer 6

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Question 7

The high radiant heat flux present causes the surface temperature of the combustible fuels within the compartment to rise, and pyrolysis gases produced.

Answer 7

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Question 8

When the hot gas layer temperature reaches approximately 590*C, a heat flux from the hot gas layer of approximately 20 kW/m2 at floor level is often present.

Answer 8

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Question 9

Flashover, which is a rapid transition of a growth phase fire to a fully developed fire, is a dangerous phenomenon and has claimed the lives of countless firefighters.

Answer 9

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Question 10

Time to flashover form ignition was as little as 3 to 5 minutes.

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Question 11

Flashover may occur multiple times in a structure as the fire progresses from one area to another with each event having a potential to impact other compartments.

Answer 11

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Question 12

In a fully developed fire, the air flow into the compartment is not sufficient to burn all of the combustibles being pyrolyzed by the fire, and the fire will shift from fuel limited to ventilation limited where the HRR is limited by the amount of oxygen available.

Answer 12

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Question 13

Although pyrolysis can continue throughout the compartment, flaming combustion will only occur where there is sufficient oxygen present.

Answer 13

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Question 14

Fully developed fires are ventilation limited.

Answer 14

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Question 15

During the development of an incipient fire, the rate of flame spread and HRR is greatly dependent on the configuration and characteristics of the fuels involved.

Answer 15

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Question 16

As radiant heat from the fire warms nearby fuels, it continues the progress of further pyrolysis, allowing the flames to continue to spread and involve more fuel surfaces, causing the fire’s HRR to increase as the fire moves into the growth stage.

Answer 16

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Question 17

As the fire burns, the gaseous products of combustion move upwards due to differences in temperature, density, and pressure between the room temperature air and the gases generated and heated by the fire, creating a fire plume.

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Question 18

As a fire develops within a compartment that is interconnected to other spaces in the structure, fluid flows develop due to the pressure differentials created by the fire.

Answer 18

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Question 19

Hot gas flows have claimed the lives of many fire fighters and ca be extremely dangerous when crews are positioned in the exhaust portion of the flow path, which is between the fire and the exhaust vent.

Answer 19

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Question 20

Exhaust portions of the flow path exist above the neutral plane and allow fire gases to exit the structure.

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Question 21

Intake portions of the flow path exist below the neutral plane and allow fresh air into the structure.

Answer 21

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Question 22

The safest position from which to mount an interior fire control is to place firefighters on the intake side of the flow path.

Answer 22

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Question 23

A bidirectional flow can often be seen at an opening positioned at the same level as the fire.

Answer 23

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Question 24

A unidirectional flow can often be seen when two openings exist at different elevations allowing the whole inlet or exhaust openings to be positioned completely below or above the neutral plane.

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Question 25

The most dangerous place for firefighters to be located is in the exhaust portion of the flow path.

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Question 26

Exhaust portions of the flow path have had gas speeds recorded up to 20mph.

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Question 27

Dynamic flow is a condition where unidirectional or bidirectional flow of smoke/air presents irregular stratification and shape or alternates in direction.

Answer 27

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Question 28

A unidirectional or bidirectional flow of smoke/air that presents irregular stratification and shape or alternates in direction is identified as dynamic flow.

Answer 28

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Question 29

Wind speeds as low as 9mph can have a significant impact on the flow behavior of the fire gases and increase the risk of fire extension and threat to human life.

Answer 29

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Question 30

Under the right conditions, the fuel to air mixture in the vicinity of the smoldering source can become ignited, and a smoke explosion occurs as a deflagration moves quickly through the premixed flammable mixture.

Answer 30

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