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CFD 11 Month > IFSTA CH 4 Fire Dynamics > Flashcards

IFSTA CH 4 Fire Dynamics Flashcards

1
Q

physical change

A

substance remains chemically the same but changes in size, shape or appearance (ex. freezing/boiling)

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2
Q

Chemical reaction

A

occurs when a substance changes from on type of matter into another

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3
Q

oxidation

A

chemical reaction involving the combination of an oxidizer with other materials

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4
Q

timeline of oxidation

A
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5
Q

potential energy

A

the amount of energy that an object can release at some point in the future

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6
Q

kinetic energy

A

energy that a moving object possesses

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7
Q

exothermic reaction

A

reactions that emit energy as they occur

ex. Fire, releases energy in the form of heat and sometimes light

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8
Q

endothermic reaction

A

reactions that absorb energy as they occur

ex. converting water to steam

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9
Q

fire triangle

A
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10
Q

Fire Tetrahedron

A
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11
Q

eliminate any of the elements in the fire triangle

A

the fire will be extinguished

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12
Q

ignition

A

fuels must be in a gaseous state in order to burn

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13
Q

pyrolysis

A

occurs when a solid fuel is converted into a gaseous fuel

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14
Q

vaporization

A

is the conversion of a liquid to a vapour by heat energy

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15
Q

piloted ignition

A

most common form of ignition

occurs when a mixture of fuel and oxygen encounter an external heat source with sufficient heat or thermal energy to start the combustion reaction

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16
Q

autoignition

A

occurs without any external flame or spark to ignite the fuel gases or vapours

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17
Q

autoignition temperature (AIT)

A

minimum temp at which a fuel in the air must be heated in order to start self-sustained combustion

always higher then its piloted ignition temperature

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18
Q

two modes of combustion

A

flaming and non-flaming

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19
Q

non-flaming combustion

A

occurs more slowly and at a lower temperature, producing a smoldering glow in the materials surface (fire triangle)

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20
Q

flaming combustion

A

commonly referred to as fire

produces a visible flame above the materials surface

occurs when a gaseous fuel mixes with oxygen in the correct ratio and heats to ignition temperature (fire tetrahedron)

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21
Q

products of combustion

A

often described as heat and smoke

materials produced and released during burning

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22
Q

incomplete combustion

A

smoke is a product of incomplete combustion

combustion is incomplete when any of the fuel is left after combustion has occurred

has the potential to burn

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23
Q

carbon monoxide

A

toxic and flammable product of the incomplete combustion of organic materials

colorless and odorless gas

acts as a chemical asphyxiant (frequent cause of death in civilians)

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24
Q

hydrogen Cyanide (HCN)

A

toxic flammable substance produced int he combustion of materials containing nitrogen

is a significant byproduct of the combustion of polyurethane foam used in many household furnishing

is 35x more toxic than CO

HCN prevents the body from using oxygen at the cellular level

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25
Q

carbon dioxide

A

is a product of complete combustion of organic materials

it displaces existing oxygen which creates an oxygen deficient atmosphere

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26
Q

pressure

A

is the force per unit of area applied perpendicular to a surface

gases always move from areas of higher pressure to areas of lower pressure

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27
Q

health effects of CO

A
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28
Q

health effects of HCN

A
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29
Q

Heat

A

is the thermal kinetic energy needed to release the potential chemical energy in a fuel

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30
Q

temperature

A

is the measure of heat

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31
Q

heat (HRR) - candle example

A

one candle burns at the same temperature as ten candles

however the heat release rate of the ten candles is 10x greater than on candle at the same temperature

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32
Q

HRR and PPE

A

the temperature tells you it is safe to go in but the heat transfer rate - not the temperature - tells you how long you can stay in

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33
Q

chemical energy

A

most common source of heat in combustion reactions

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34
Q

self-heating

A

a form of oxidation

is a chemical reaction that increases the temperature of a material without the addition of external heat

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35
Q

spontaneous ignition

A

ignition without the addition of external heat

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36
Q

electrical energy can occur in several ways, including

A

resistance heating
overcurrent or overload
arcing
sparking

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37
Q

resistance heating - electrical

A

electric current flowing through a conductor produces heat

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38
Q

overcurrent or overload - electrical

A

when the current flowing through a conductor exceeds its designed limits

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39
Q

arcing

A

high-temp electric discharge across a gap or through a medium

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40
Q

sparking - electrical

A

when an electric arc occurs, glowing particles can form and splatter away from the arcing point

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41
Q

temperature - Celsius/Fahrenheit conversion

A
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42
Q

mechanical energy

A

friction and compression generate mechanical energy

movement of two surfaces against each other

compressed gas

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43
Q

heat transfers from

A

warmer objects to cooler objects

44
Q

Heat transfers in 3 ways

A

conduction
convection
radiation

45
Q

conduction

A

transfer of heat through and between solids

a material is heated as a result of direct contact with a heat source

46
Q

Convection

A

transfer of thermal energy by the circulation or movement of a fluid

47
Q

convection - vertical movement

A

due to the buoyancy of smoke and fire gases

48
Q

convection - lateral movement

A

usually the result of pressure differences between

49
Q

radiation

A

transmission of energy as electromagnetic waves

travels in a straight line at the speed of light (ex. sun)

common cause of exposure fires

50
Q

fuel

A

is the oxidized or burned material or substance in the combustion process

fuel in a combustion reaction is known as the reducing agent

51
Q

gases

A

for flaming combustion to occur, fuels must be in a gaseous state

52
Q

HRR in watts

A
53
Q

vapor density

A

describes the density of gases in relation to air

air has a vapor density of 1

54
Q

gases of a vapor density less than one will

A

rise

55
Q

gases of a vapor density greater than 1 will

A

sink

56
Q

liquids

A

have mass and volume but no definite shape

57
Q

specific gravity

A

ratio of the mass of a given volume of a liquid compared to the mass of an equal volume of water at the same temperature

water is assigned a specific gravity of 1

58
Q

specific gravity of less than 1 will

A

float

59
Q

specific gravity of greater than 1 will

A

sink

60
Q

flash point

A

is the minimum temperature at which a liquid gives off sufficient vapors to ignite but not sustain combustion in the presence of a piloted ignition source

61
Q

fire point

A

the temperature at which a piloted ignition of sufficient vapors will begin a sustained combustion reaction

62
Q

solubility

A

describes the extent to which a substance will mix with water

63
Q

miscible

A

materials that are miscible in water will mic in any proportion

64
Q

polar solvents

A

flammable liquids that have an attraction to water

will mix readily with water

65
Q

solids

A

have a definite size and shape

66
Q

surface-to-mass ratio

A

ratio of the surface area of the fuel to the mass of the fuel

as the ratio increases, the particles ability to ignite increases

67
Q

oxygen

A

primary oxidizing agent in most fires

normally air consist of about 21% oxygen

68
Q

flammable (explosive) range

A

range between the upper flammable limit and lower flammable limit in which a substance can ignite

69
Q

lower explosive (flammable) limit

A

minimum concentration of fuel vapor and air that supports combustion

to lean to burn

70
Q

upper explosive (flammable) limit

A

concentration above which combustion cannot take place

too rich to burn

71
Q

chemical flame inhibition

A

occurs when an extinguishing agent, interferes with this chemical reaction, forms a stable product and terminates the combustion reaction

72
Q

fuel limited

A

when sufficient oxygen is available for flaming combustion

incipient stage = fuel limited

73
Q

ventilation-limited

A

have access to all the fuel need to maintain combustion

the fire does not have access to enough oxygen to continue to burn

74
Q

stages of fire development

A

incipient stage
growth stage
fully developed stage
decay stage

75
Q

three key factors that control how the fire develops

A

fuel properties
ventilation available
heat conservation

76
Q

flammable (explosive) range photo

A
77
Q

surface-to-mass ratio photo

A
78
Q

incipient stage

A

starts with ignition (where the fire begins)

fuel-limited fire

portable extinguishers or small hose line can extinguish

79
Q

ceiling jet

A

hot gases in the plum rise until they encounter the ceiling, then begin to spread horizontally

80
Q

growth stage

A

a visual indicator that a fire is leaving the incipient stage is flame height

when flame reach 2.5 feet high, radiant heat begins to transfer more than convection

can become vent-limited or fuel limited

81
Q

fuel package location and entrainment of air

A
82
Q

Thermal layering

A

the tendency of gases to form into layers according to temperature, gas density and pressure

83
Q

neutral plane

A

interference between the hot gas layers and cooler layer of air

net pressure is zero where the layers meet

84
Q

rapid fire development

A

refers to the rapid transition from the growth stage or early decay stage to a ventilation-limited fully developed stage

85
Q

flashover

A

rapid transition from the growth stage to the fully developed stage

the combustible materials and fuel gases in the compartment ignite almost simultaneously

changes from a two-layer condition to a single (untenable)

86
Q

rollover

A

significant indicator of flash over

condition where unburned fire gases that have accumulated at the top of the compartment ignite and flames propagate through the hot gas layer or across the ceiling

87
Q

four common elements of flashover

A

transition in fire development
rapidity
compartment
pyrolysis of all exposed fuel surfaces

88
Q

fully developed stage

A

occurs when the heat release rate of the fire has reached its peak because of a lack of either fuel or oxygen

89
Q

backdraft

A

an increase in ventilation such as opening door or window can result in an explosively rapid combustion of the flammable gases

occurs in a space containing a high concentration of heated flammable gases that lack sufficient oxygen for flaming combustion

90
Q

fuel-limited conditions

A

the available fuel limits the peak heat in a fuel-limited, fully developed fire

ex. campfire

91
Q

ventilation-limited conditions

A

lacks the oxygen available to grow

92
Q

decay stage

A

runs out of available fuel or oxygen

93
Q

flow path

A

composed of two regions

  • ambient air flow in
  • hot exhaust flow out

unidirectional due to pressure differences

94
Q

smoke explosion

A

occurs when a mixture of unburned fuel gases and oxygen comes in contact with an ignition source

95
Q

effects of firefighting operations

A

temperature reduction
fuel removal
oxygen exclusion
chemical flame inhibition

96
Q

temperature reduction

A

using foam or water to cool

97
Q

fuel removal

A

typically a tactic in wildland, liquid and gas fires

98
Q

oxygen exclusion

A

flow path control

door control/tactical ventilation

99
Q

chemical flame inhibition

A

using extinguishing agents other than water and foam to interrupt the combustion reaction and stop flame production

ex dry chemicals

100
Q

fuel load

A

total quantity of combustible content of a building, space or fire area

101
Q

compartments

A

any open space with no complete fire barrier dividing is considered a compartment

compartmentation - layout of the various open spaces in a structure

102
Q

pulsing smoke

A

backdraft

103
Q

rollover

A

flashover

104
Q

flashover indicators

A

increase temperature
rollover
lowering of hot gas layer (neutral plane)

105
Q
A

CFD 11 Month (32 decks)

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