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Fire Academy > Ch. 4 - Fire Dynamics (Test 4) > Flashcards

Ch. 4 - Fire Dynamics (Test 4) Flashcards

1
Q

Even though there are fewer fires today than there were in the late 1970’s, there are more firefighters dying as a result of traumatic fireground injuries. ______

A

(+67%)

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2
Q

(2014-2017)

Average of 295,975 fires per year ________________.

A

(58% decrease)

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3
Q

(2014-2017)

Average of 2,728 civilian deaths ________________

A

(53% decrease)

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4
Q

Despite there being countless examples of fire being mystified, stylized or humanized but the truth is:

______________________________

A

Fire is insentient

Devoid of all intent and/or emotion

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5
Q

_________ - A rapid oxidation process, which is a chemical reaction resulting in the evolution of light and heat in varying intensities. (NFPA 921)

A

Fire

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6
Q

___________ - A self-sustaining chemical process of oxidation that occurs at a rate fast enough to produce heat and light. (i.e. a glow of a flame) – NFPA 921

A

Combustion

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7
Q

For generations, firefighters were taught that for fire to exist, only three (4) essential items needed to be present. Those elements are/were:

__________
__________
__________

A

Fuel
Oxidizing Agent
Heat (Activating energy)

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8
Q

For fire to exist, fuel, oxidizer, AND heat must interact in a such a way so as to for a _________________.

A

Sustained chemical reaction

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9
Q

The reaction we understand to be fire, is actually a _______________ reliant upon countless variables.

A

Complex chemical process

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10
Q

In the most general of terms, fuel is ______________.

A

Consumable matter

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11
Q

Matter exists in one of three physical states:

_________
_________
_________

A

Solid
Liquid
Gas

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12
Q

It’s ___________ (and density) can be altered by changes in:

-__________
and/or
-__________

A

-physical state

  • temperature
  • pressure
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13
Q

What happens to a substance when it changes its physical state? Does its molecular structure change? ____, only the distance between molecules changes

A

No

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14
Q

Density can be defined as:

A measure of the ___________ of a substance.

A

Compactness

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15
Q

(Density)

It affects matter’s ability to ________________ heat.

A

Absorb, transfer, and release

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16
Q

Solid fuels do not burn. They release flammable gases through _________, which is the chemical decomposition of solids through the action of heat.

A

Pyrolysis

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17
Q

Pyrolysis is ___________ by nature.

A

Endothermic

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18
Q

A few characteristics that affect solid fuels ability to generate ignitable gases.

  • ______________
  • ______________
  • ______________ to heat source
  • ______________
  • ______________ of fuel
  • ______________
  • ______________
A
  • Density
  • Surface area to mass ratio
  • Physical position/orientation
  • Size and shape
  • Continuity
  • Ignition temperature
  • Level of Exposure
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19
Q

Liquid fuels do not burn either. They release ignitable ashes through the process of ____________, which is the process of changing liquid matter into gaseous matter through variances in ___________________.

A
  • vaporization

- temperature and/or pressure

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20
Q

A few characteristics that effect solid fuels ability to generate ignitable gases:

  • ____________
  • ____________
  • ____________
  • ____________
  • ____________
  • ____________
A
  • Volatility
  • Vapor Pressure
  • Boiling Point
  • Specific Gravity
  • Solubility
  • Fire Point
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21
Q

___________ - The ease with which a substance passes into a gaseous state at a given temperature and pressure.

A

Volatility

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22
Q

Volatility is determined by:

  • ___________
  • ___________
  • ___________
A
  • Flash point
  • Exposed surface area
  • Pressure
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23
Q

____________ - The lowest temperature at which a fuel will give off sufficient flammable vapors to ignite momentarily when provided with an external ignition source.

A

Flash point

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24
Q

Atmospheric pressure at sea level is: _____.

Atmospheric pressure in Salt Lake City is approx. _____.

A
  1. 7 psi

12. 5 psi

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25
Q

__________ - The pressure exerted by vapors at the point of __________ with its solid or liquid state (There is no net loss to evaporate).

A
  • Vapor Pressure

- equilibrium

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26
Q

____________ - The temperature at which the vapor pressure of a liquid ________ atmospheric pressure.

A
  • Boiling point

- exceeds

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27
Q

_________ - Water is used as a constant for comparison to other liquids and is given the relative value of one (1):

Any liquid with a density of ________ will sink.

Any liquid with a density of ________ will rise.

A

-Specific Gravity

  • greater than one
  • less than one
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28
Q

__________ - The relative ability of a substance to be dissolved into water.

A

Solubility

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29
Q

__________ - The lowest temperature at which a liquid fuel will produce sufficient vapors to ignite and support combustion for at least 5 seconds.

A

Fire point

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30
Q

Gaseous fuels ___________ vaporization of pyrolysis to support combustion.

Only an ___________ AND a proper mixture of an __________ is needed.

A

-do not require

  • ignition source
  • oxidizer
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31
Q

Characteristics that effect gaseous fuels:

  • _______________
  • _______________
A
  • Vapor Density

- Flammable Limits

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32
Q

Any gas with a density __________ will sink.

A

Greater than 1.0

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33
Q

Any gas with a density ___________ rise.

A

Less than 1.0

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34
Q

There are only _________ gases with vapor density of less than one (1).

A

Fourteen (14)

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35
Q

Most ____________ fuel vapors are heavier than air.

A

Hydrocarbon

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36
Q

Flammable Limits: The range of flammable vapors in air, expressed by percentages; that will ignite when provided an ignition source

The area between the lower and upper limits are known as the fuel’s:
_________________

A

Flammable range

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37
Q

(Flammable Limits)

At what point an environment containing ignitable vapors may be considered _______ but still hazardous.

A

inert

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38
Q

The concept of ignitable gases acting to inert a flammable/combustible environment applies only:

  • _______________
  • To areas so _______________ to fuel sources as to displace or exclude all oxygen.
A
  • To closed containers

- immediately adjacent

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39
Q

_____________ - A measurement of the potential fire threat of a given structure.

A

Fire load

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40
Q

Since the 1970’s, the average single-family dwelling in this country has:

  • Seen a ___________ in the number of occupants living within them
  • Increased in size by nearly _____

-Transitioned from primarily single-story structures to primarily 2-story structures
—____ increase in number of 2-story homes built
—____ decrease in the number of 1-story homes built

A
  • 20% decrease
  • 73%
  • 143%
  • 52%
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41
Q

How has the fire load of modern structures changed?

  • Home sizes have changed
  • _______________
  • Structural resistance has changed
  • Energy Density
  • _______________
A
  • Contents have changed

- Heat Release Rate (HRR)

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42
Q

(Energy Density)

______________ - The amount of heat released per unit of mass or volume until of a substance at the end of a complete combustion process.

A

Heat of Combustion

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43
Q

(Heat Release Rate [HRR])

HRR is ________________________ when describing a fire problem

The __________________________ to life

A
  • the single most important variable

- higher the HRR the greater the threat

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44
Q

(Heat Release Rate [HRR])

The __________________________ to life

A

higher the HRR the greater the threat

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45
Q

These increases in energy density and heat release rates result in:

Greater __________ measurements.

A

heat flux

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46
Q

Essentially, the fuel changes are:

Greater quantities
More energy dense
Higher HHRs

……resulting in:

Greater heat flux

OR

More ___________________

A

Heat making more heat

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47
Q

Does this “Heat making more heat” mean that fires are hotter now than they were in the 1970’s?

___________

A

Yes & No

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48
Q

While today’s fire environments are:

________ hotter as a result of changes to compartmental heat loss…

The actual temperature of flaming combustion has not changed that much.

A

Up to 26%

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49
Q

Rather…

It is the _________ of these fires that has dramatically increased.

Resulting in:

  • ________________
  • Increased requirements for oxygen
  • Drastically shortened burn times
A
  • power (HRR)

- More rapid consumption of fuels

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50
Q

__________ is the most common oxidizer

A

Oxygen

51
Q

Atmospheric air is comprised of:

__________
__________
__________

A

21% oxygen
78% nitrogen
1% other gases

52
Q

___________ - A reactant that removes electrons from other reactants during a redox reaction.

A

Oxidizer

53
Q

(Oxidizing Reactions)

These redox reactions can occur very slowly
—______

Very quickly
—______

A
  • Rust

- Explosions

54
Q

___________ - The complete chemical reaction of organic materials with oxygen or other oxidizing agents resulting in the formation of more stable chemical compounds.

A

Oxidation

55
Q

Only a relatively small amount of energy is required to start the reaction resulting in a larger energy release making ______________________.

A

oxidation an exothermic process

56
Q

___________ - A chemical reaction that releases more heat energy than it uses.

A

Exothermic

57
Q

__________ - A chemical reaction that absorbs more heat energy than it releases.

A

Endothermic

58
Q

Oxidation Variables:

  • ___________
  • ___________ of available oxidizing agent - Higher concentrations of oxidizer result in more redox reactions
  • ___________ - The greater the exposed surface area, the greater the number of simultaneous redox reactions
  • ___________ - Excess compounds in the atmosphere may prevent block the pathways of energy preventing or limiting the sustainment of redox reactions.
A
  • Temperature
  • Quantity
  • Interface Area
  • Accessibility
59
Q

Accessibility– Excess compounds in the atmosphere may prevent block the pathways of energy preventing or limiting the sustainment of redox reactions. These compounds are commonly referred to as:

_______________ – Any substance occupying space and capable of absorbing heat resultant of a redox reaction.

A

Thermal Ballast

60
Q

TRUE OR FALSE

The terms Heat and Temperature are synonymous?

A

False

61
Q

_____________ – is a measurement of the average kinetic energy caused by the movement of molecules within a substance.

A

Temperature

62
Q

_______ – is the form of energy that ____________________ of molecules.

A
  • Heat

- raises the average kinetic energy

63
Q

(Sources of Heat Energy) Chemical

___________ source of heat energy in combustion reactions

A

Most common

64
Q

(Sources of Heat Energy) Chemical

Chemical heat energy is produced by ______________

A

oxidation reactions

65
Q

Forms of Chemical Heat Energy:

  • ______________
  • ______________
  • ______________
  • ______________
A
  • Heat of Combustion
  • Heat of Solution
  • Spontaneous Heating
  • Heat of Decomposition
66
Q

(Sources of Heat Energy) Mechanical

Forms of Mechanical Heat Energy:

________ - the force that resists the relative motion or tendency to such motion of two bodies in contact.
________ - the application of continuous force by one body on another that it is touching

A
  • Friction

- Pressure

67
Q

(Sources of Heat Energy) Nuclear

Forms of Nuclear Heat Energy
______ - a thermonuclear reaction in which nuclei of light atoms join to form nuclei of heavier atoms.

______ - the splitting of the nuclear of an atom into nuclei of lighter atoms, accompanied by the release of energy.

A
  • Fusion

- Fission

68
Q

Heat (energy) will flow from areas of higher concentration to areas of lower concentration in an attempt to balance itself out.
—This transfer will occur in several ways:

______________
______________
______________

A

Conduction
Convection
Radiation

69
Q

____________ - Transfer of heat energy from _____________________.

A
  • Conduction

- one material/molecule to another

70
Q

Variables of Conduction:

  • ______________
  • ______________
  • ______________
  • ______________
A
  • Thermal Conductivity (k)
  • Temperature
  • Mass
  • Exposure
71
Q

____________ - Transfer of heat energy from one point to another through _____________________.

A
  • Convection

- the movement of liquids and/or gases

72
Q

Convection is the _________________ inside a structure.

A

main reason for fire spread

73
Q

There are two distinct mechanisms of convective heat transfer:

___________
___________

A

Natural

Forced

74
Q

(Mechanisms of heat transfer) Natural

Velocity of flowing gas it controlled by _________________

A

buoyancy-induced flows

75
Q

(Mechanisms of heat transfer) Forced

The velocity of flowing gas is __________________________

A

artificially imposed (fan, wind, fire stream)

76
Q

_____________ - Fluid compounds (liquids and gases) will stratify within a given space based upon temperature and density.

A

Stratification

77
Q

____________ - Heated fire gases and smoke will rise as long as their temperature remains higher than the surrounding atmosphere. Once either the temperatures equalize or rising gases and smoke impact the ceiling within the space, rising pressure from continued combustive by-products will force the gases and smoke to push outward along a horizontal plane and begin to bank down and stratify.

A

Mushrooming

78
Q

____________ - Transfer of heat energy from one material to another by _______________ without the need of an intervening medium.

A
  • Radiation

- electro-magnetic waves

79
Q

Variables of Radiation:

  • ___________
  • ___________
  • ___________
  • ___________
A
  • Color/Opacity
  • Position
  • Distance
  • Temperature
80
Q

The first phase of fire development is:

_________ - The process of initiating self-sustaining combustion

A

Ignition

81
Q

Ignition requires:

Sufficient ______ to initiate and sustain the combustion reaction.

A source of _____ either in an immediately ignitable state or one capable of converting to this state with available heat.

An adequate supply of ______ or another oxidizing agent.

A

heat
fuel
oxygen

82
Q

With enough heat, the available fuel gases will ignite and begin the combustion process.

The amount of heat required depends upon the fuel’s:

___________________
___________________

A
  • Piloted Ignition Temperature

- Auto-Ignition Temperature

83
Q

____________________ - The minimum temp at which a solid fuel will give off sufficient flammable/combustible vapors in air capable of sustained combustion if supplied with an external ignition source.

A

Piloted Ignition Temperature

84
Q

______________________ - The minimum temp at which a solid fuel will give off sufficient flammable/combustible vapors in air capable of sustained combustion without an external ignition source.

A

Auto-Ignition Temperature

85
Q

What is the temperature of Carbon Monoxide’s Auto-Ignition Temperature?

A

1128º F

86
Q

The piloted ignition temperature is generally ____________ than the auto-ignition temperature.

A

significantly lower

87
Q

Once the fuel has reached its ignition temperature and flaming combustion has commenced, the fire is said to be in its incipient stage. In this stage, continued growth will depend upon the following variables:

  • _______________
  • _______________
  • _______________
  • _______________
  • _______________
A
  • Compartment Design
  • Location of fuel
  • Fuel Composition
  • Availability of Oxygen
  • Time/Duration of Exposure
88
Q

A fire in its Incipient State present with:

  • __________________
  • ____________ usually seen on windows in or near the fire compartment
  • Fire that is small in size
  • Little to no development of a _________ or accumulation of hot gases at the top of the compartment
A
  • Low compartmental heat
  • Condensation
  • flow path
89
Q

(Incipient Stage) Characteristics

  • ____________________
  • Heated gases rise and mix with and/or _________________
A
  • Little if any visible smoke

- displace cooler gases

91
Q

(Growth Stage)

The ease/speed at which a fire grows depends largely upon the following variables:

  • _______________
  • Heat
  • _______________
  • _______________
A
  • Available fuel
  • Compartment Design
  • Air/Oxygen
92
Q

(Growth Stage) Heat is:

_____________________

A

Heat is the driving factor in fire growth

93
Q

(Growth Stage) Air/Oxygen

Fire grows in ______________ to the volume of oxidizer (air) available to it.

A

direct proportion

94
Q

A fire in its Growth Stage will present with:

  • _______________
  • Condenstaion seen during the incipient stage will be replaced with _______________ and/or _________________ near the fire
  • Fire that has dramatically increased in size
  • Increased smoke and gas production dust to ______________
A

-Increased compartmental heat

  • brownish black staining
  • cracks in upper panes of glass

-incomplete combustion

95
Q

____________ - As fire gases, near the ceiling, reach ignition temp and enter into their flammable range, flames spread through the gases in wave or snake-like patterns

A

Rollover

96
Q

(Rollover) Increase in flames cause increases in compartmental:

  • ___________
  • ___________
  • ___________
A
  • Pressure
  • Heat
  • Heat Transfer
97
Q

(Rollover)

_________ - Forces smoke and gases to extend beyond the compartment (Down the hall)

A

Pressure

98
Q

(Rollover)

_______ - Increased flames create greater liberation of heat and light. All elements within the compartment are pushed to near auto-ignition temp.

A

Heat

99
Q

(Rollover)

___________ - Compartment walls, ceiling, and contents are bombarded with an ever-increasing amount of heat.

A

Heat Transfer

100
Q

If the fire/compartment cannot be/is not cooled, the fireground phenomenon ____________ will occur.

A

FLASHOVER

101
Q

Remember, flashover is a _____________ in fire development as opposed to a truss stage

A

transitional phase

102
Q

In order for flashover to occur, a few conditions must be present:

Ceiling temperature within the compartment must reach __________

A

500-600º C

103
Q

In order for flashover to occur, a few conditions must be present:

Average Heat Flux to the floor of the compartment must reach __________

A

15-20 kW/m^2

104
Q

In order for flashover to occur, a few conditions must be present:

Sufficient _________ must be available to support the increased rate of combustion

A

oxygen

105
Q

In order for flashover to occur, a few conditions must be present:

_____________________

Once the walls and ceilings have absorbed all the heat they possibly can, they begin to_______________ back into the space, switching from _______________________.

This radiation feedback _______________________ resulting in a drastic spike in room and content temperature

A
  • Thermal Radiant Feedback
  • re-radiate heat
  • endothermic to exothermic
  • dramatically increases heat flux
106
Q

An impending flashover will present with:

_______________ exiting through openings in the container

____________ inside the compartment with visible off-gassing of uninvolved objects

Isolated flames traveling in the hot gas layer __________ or increasing concentration of _________

A
  • Intense turbulent smoke
  • Intense heat
  • ghosting
  • rollover
107
Q

Variables Affecting Flashover:

  • _______________
  • _______________
  • _______________
  • _______________
A
  • Room Geometry
  • Conductivity/Flammability of walls and ceiling
  • Contents
  • Rate of heat release
108
Q

Cellulose materials release and average of __________________

Synthetic materials release between _______________________

A
  • 9000 BTUs per pound

- 12,000 to 18,000 BTUs per pound

109
Q

Rate of Heat Release - Equation based on type, quantity, and location of materials involved in fire.

________________________________

A

This is the single most important factor concerning flashover

110
Q

A fire in its fully developed stage will present with:

Voluminous smoke:
_________ (Gray, brown, or black)
_________ through the predominant flow path

A
  • Dark in color

- Driven by heat

111
Q

A fire in its fully developed stage will present with:

A well-defined and strong flow path:
-In this state, the fire is _____________ and increasing the amount of available air will increase the size of the fire and the volume of heat.

A

ventilation limited

112
Q

A fire in its fully developed stage will present with:

Fire that’s producing substantial heat:
_____________ (1292-2192º F)

A

700-1200º C

113
Q

A fire in its fully developed stage will present with:

As the fire’s fully developed stage progresses,
_________________ continues to increase

A

the potential for collapse

114
Q

Variables that effect a fully developed fire:

  • Access to _________
  • Its supply of _______
  • _______
A

oxygen
fuel
Heat

115
Q

(Decay) A fully developed fire that is confined or that stays compartmentalized will transition into the decay phase though one of three routes:

  • ___________________________
  • The amount of available ____________________________
  • ________________ and transferred out through the structure
A
  • All available fuel is consumed
  • oxidizer falls below sustainable levels
  • Heat balance is lost
116
Q

(Decay) If the fire enters an oxidizer-induced decay phase as a result of its container:

  • The fire’s heat release rate will decline in ________________ with the amount of available oxidizer
  • Temperature within the compartment may ________________ (temporary)
  • Fuels will continue to ______________ – releasing ignitable gases

Compartmental pressure will continue to increase.
—>Up to a ________

A
  • direct correlation
  • continue to rise
  • vaporize/pyrolyze
  • 3:1 ratio
117
Q

Eventually, the fire will self-extinguish and minimize the hazard as long as oxygen is not reintroduced.

If, oxygen is reintroduced however, a __________ may occur.

A

backdraft

118
Q

Backdraft definition:

The __________________ to a confined area, that is pressurized with heated flammable gases, resulting in an explosive force of significant intensity.

A

reintroduction of oxygen

119
Q

(Backdraft) Precursors to backdraft capable environments:

  • ______________
  • ______________
  • ______________
A
  • Ventilation controlled states
  • Available Heat
  • Available Fuel
120
Q

Indicators of a possible backdraft:

-Fire in a _____________ or _____________

-Smoke
——___________
——Appears to be _____________ from the structure

-Air
________ rapidly into the structure

-Doors/Windows
_____ to the touch

A
  • ventilation controlled
  • late decay state
  • Issuing under pressure
  • breathing of puffing
  • Being drawn
  • Hot
121
Q

(Backdraft) Sequence of Events:

__________________ of oxygen to the confined fire space

A

Improper reintroduction

122
Q

(Backdraft) Sequence of Events:

___________________ needs to contain an explosive mix for backdraft to occur

A

Only 25% of total space

123
Q

(Backdraft) Sequence of Events:

Super-hearted gases ignite in an _____________________

A

explosive combustion process

124
Q

(Results of Backdraft)

  • ____________ will explosively press toward ventilation opening
  • ____________ capable of breaking glass, damaging/injuring objects and personnel in its path
  • _____________
  • Room of backdraft origin ________________________
A
  • Fireball/smoke
  • Shockwave
  • Possible collapse
  • returns to fully developed state
125
Q

Rollover is the _____________ an area if an effective hose stream is not in place and operating.

A

last sign to leave

Fire Academy (14 decks)

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