Chap 1 Flashcards
Fire Dyamics (155 cards)
1
Q
__ __ describes the meeting point between fire science, materials science, fluid dynamics of gases, and heat transfer
A
Fire dynamics
2
Q
All fires involve a heat producing chemical reaction between some type of __ and an __, most commonly __ in the air
A
Fuel
Oxidizer
Oxygen
3
Q
Calcium hypochlorite, chlorine, ammonium nitrate, hydrogen peroxide, and methyl ethyl ketone peroxides are all..
A
Common oxidizers
4
Q
A chemical process of oxidation that occurs at a rate fast enough to produce heat and usually light in the form of a glow or a flame
A
Combustion
5
Q
A rapid oxidation process, which is a gas phase chemical reaction resulting in the evolution of light and heat
A
Fire
6
Q
Form of energy associated with the motion of atoms or molecules in solids or liquids that is transferred from one body to another as a result of a temp difference between the bodies
A
Heat
7
Q
Measure of a avg kinetic energy of the particles in a sample of matter, expressed in terms of units or degrees designated on a standard scale
A
Temperature
8
Q
Physical science is the study of __ and __ and includes chemistry and physics
A
Matter
Energy
9
Q
__ change occurs when a substance remains chemically the same but changes in size, shape, or appearance (water freezing (liquid to solid) and boiling (liquid to gas))
A
Physical
10
Q
A __ __ occurs when a substance changes for one type of matter into another, such as two or more substances combining to form compounds
A
Chemical reaction
11
Q
A material that will maintain combustion under specified environmental conditions
A
Fuel
12
Q
Any material that readily yields oxygen or other oxidizing gas, or that readily reacts to promote or initiate combustion of combustible materials
A
Oxidizer
13
Q
Anything that occupies space and has mass
A
Matter
14
Q
Capacity to perform work; occurs when a force is applied to an object over a distance, or when a substance undergoes a chemical, biological, or physical transformation
A
Energy
15
Q
Chemical process that occurs when a substance combines with an oxidizer
A
Oxidation
16
Q
The rate at which fuel releases energy over time depends on many variables including:
A
Chemical composition
Arrangement
Density of fuel
Available oxygen for combustion
17
Q
A fuels __ energy is the result of virbrations in molecules
A
Kinetic
18
Q
Stored energy possessed buy and object that can be released in the future to perform work once released
A
Potential energy
19
Q
Total amount of thermal energy (heat) that could be generated by the combustion (oxidation) reaction if a fuel were completely burned.
A
Heat of combustion
20
Q
The heat of combustion is typically measured in..
A
Kj/g or MJ/kg
21
Q
Energy possessed by a moving object because of its motion
A
Kinetic energy
22
Q
Kinetic energy associated with the random motions of the molecules of a material or object; often used interchangeably with the terms heat and heat energy
A
Thermal energy
23
Q
Types of energy:
A
Chemical
Thermal
Mechanical
Electrical
Light
Nuclear
Sound
24
Q
Energy is measured in __ in the International System of Units (SI)
A
Joules (J)
25
The quantity of heat required to change the temp of 1 gram of water by 1 degree Celsius is..
4.2 joules
26
In the customary system, the unit of measurement for heat is the..
British thermal unit (Btu)
27
The amount of heat required to raise 1 pound of water 1 degree Fahrenheit is..
Btu
28
1055 J is equal to..
1 Btu
29
1 calorie is equal to..
4.19 J
30
Reactions that emit energy
Exothermic reactions
31
Reactions that absorb energy
Endothermic reactions
32
Unit of work or energy in the International System of Units (SI); the energy (or work) when a unit force (1 newton) moves a body through a unit distance (1 meter)
Joule ( J )
33
Chemical reaction between two or more materials that changes the materials and produces heat
Exothermic reaction
34
Chemical reaction in which a substance absorbs heat
Endothermic reaction
35
Chemical decomposition of a solid material by heating. Precedes combustion of a solid fuel
Pyrolysis
36
Physical process that changes a liquid into a gaseous state; the rate depends on the substance involved, heat, pressure, and exposed surface area
Vaporization
37
Moment when a mixture of fuel and oxygen encounters an external heat source with sufficient heat or thermal energy to start the combustion reaction
Piloted ignition
38
Initiation of combustion by heat but without spark or flame
Autoignition
39
The lowest temp at which a combustible material ignites in air without spark or flame
Auto ignition Temp (AIT)
40
The auto ignition temp of a substance is always __ than its piloted temp
Higher
41
Two modes of combustion
Flaming
Nonflaming
42
__ __ occurs more slowly and at a lower temp producing a smoldering glow in the materials surface
Nonflaming combustion
43
__ __ is commonly referred to as fire. Produces a visible flame above the materials surface
Flaming combustion
44
To draw in and transport solid particles or gases by the flow of a fluid
Entrain
45
Materials produced and released during burning
Products of combustion
46
Result of inefficient combustion of a fuel; the less efficient the combustion, the more products of combustion are produced rather than burned during the combustion process
Incomplete combustion
47
Fuels in which the energy of combustion derives principally from carbon
Carbon-based fuels
48
Petroleum based organic compound that contains only hydrogen and carbon; may also be used to describe those materials in a fuel load which were created using hydrocarbons such as plastics or synthetic fabrics
Hydrocarbon fuel
49
Heat and smoked are described as..
Products of combustion
50
Smoke is an aerosol comprised of gases, vapor, and..
Solid particulates
51
Smoke is a byproduct of..
Incomplete combustion
52
Examples of left over fuel from incomplete combustion..
Smoke and ash
53
Unburned fuel is smoke, and it has the potential to..
Burn
54
When the air supply is __, the level of incomplete combustion is __, which produces more smoke
Limited
Higher
55
__ is composed of a wide range of toxic and flammable gases and particulates
Smoke
56
Fatal condition caused by severe oxygen deficiency and an excess of carbon monoxide and/or other gases in the blood
Asphyxiation
57
Colorless, toxic, and flammable liquid until it reaches 79 degrees F. Above that it becomes a gas with a faint odor similar to bitter almonds
Hydrogen Cyanide (HCN)
58
Acts as a chemical asphyxiant. It’s molecules attach to hemoglobin, decreasing the bloods ability to carry oxygen
CO
59
CO combines with hemoglobin about __ times more effectively than oxygen
200
60
HCN is __ times more toxic than CO
35
61
HCN prevents the body from using __ at the cellular level
Oxygen
62
Colorless, odorless, heavier than air gas that neither supports combustion nor burns
CO2
63
Force per unit area exerted by a liquid or gas measured in psi or kPa
Pressure
64
The tendency or capacity of a liquid or gas to remain afloat or rise
Buoyant
65
Total amount of heat released per unit time. Typically measured in kW or MW
HRR
66
The measure of the rate of heat transfer to or from a surface. Typically expressed in kW/m2
Heat flux
67
Result of Exothermic reactions, occurring spontaneously in some materials under certain conditions, where heat is generated at a rate sufficient to raise the temp of the material
Self-Heating
68
Initiation of combustion of a material by an internal chemical or biological reaction that has produced sufficient heat to ignite the material
Spontaneous ignition
69
Gases always move from areas of __ pressure to __ pressure
Higher
Lower
70
__ is the thermal kinetic energy needed to release the potential chemical energy in a fuel
Heat
71
Temperature is the measurement of the avg __ __ in the particles of a sample of matter
Kinetic energy
72
__ energy is the most common source of heat in combustion reactions
Chemical
73
The oxidation process almost always results in the production of __ energy. The energy dissipates almost as quickly as it is generated.
Thermal
74
Friction or compression generates __ energy
Mechanical
75
__ is generated when a gas is compressed
Heat
76
The transfer of heat from one point or object to another is part of the study of __
Thermodynamics
77
Thermal equilibrium is where all areas of an object are a uniform..
Temperature
78
The rate at which heat transfers is related to the temperature differential of the bodies and the __ __ of the materials involved
Thermal conductivity
79
__ is the transfer of heat through and between solids
Conductivity
80
Heat transfer due to conduction is dependent upon 3 factors:
-Area being heated
-Temp difference between heat source and the material being heated
-Thermal conductivity of the heated material
81
Insulating materials slow the __ of heat from one solid to another
Conduction
82
__ is the transfer of thermal energy by the circulation or movement of a fluid (fluid or gas)
Convection
83
The point at which 2 regions that are in thermal contact no longer transfer heat between them because they have reached the same temp
Thermal equilibrium
84
The propensity of a material to conduct heat within its volume
Thermal conductivity
85
Physical flow or transfer of heat energy from one body to another, through direct contact or an intervening medium, from the point where the heat is produced to another location, or from a region of high temp to a region of low temp
Conduction
86
Transfer of heat by the movement of heated fluids or gases, usually in an upward direction
Convection
87
Transmission or transfer of heat energy from one body to another body at a lower temp through intervening space by electromagnetic waves
Radiation
88
Radiated heat energy travels in a straight line at the __ __ __
Speed of light
89
Radiation is a common cause of..
Exposure fires
90
A fire ignited in fuel packages or bldgs that are remote from the initial fuel package or bldg of origin
Exposure fire
91
Fuel that is being oxidized or or burned during combustion
Reducing agent
92
Amount of energy delivered over a given period of time. And the rate at which energy transfers.
Power
93
The SI unit of power or rate of work equal to 1 joule per second (J/s)
Watt (W)
94
A multiple of thousands
Kilo
95
A multiple of millions
Mega
96
__ describes the density of gases in relation to air.
Vapor density
97
Air has a vapor density of..
1
98
The vapor density of gas provides an indication of where a gas will __ at an incident
Collect
99
__ __ is the ratio of the mass of a given volume of a liquid compared to the mass of an equal volume of water at the same temp.
Specific gravity
100
Water is assigned a specific gravity of..
1
101
The specific gravity of a liquid indicates whether the liquid will __ on the surface of water or __
Float
Sink
102
__ __ is the min temp at which a liquid gives off sufficient vapors to ignite, but not sustain combustion, in the presence of a piloted ignition source
Flash point
103
__ __ is the temp at which a piloted ignition of sufficient vapors will begin a sustained combustion reaction
Fire point
104
Flammable liquids called polar solvents such as alcohols (methanol, ethanol) will readily..
Mix with water
105
Materials that are __ in water will mix in any proportion
Miscible
106
Pyrolysis of wood begins at temps below __
400*F
107
The energy release in fire is directly proportional to the amount of __ available for combusiton
Oxygen
108
At normal ambient temps (68*F), materials can ignite and burn in oxygen concentrations as low as __
15%
109
Range between the upper and lower flammable limits in which a substance can ignite
Flammable (explosive) range
110
As flaming combustion occurs, the molecules of a fuel gas and oxygen break apart to form..
Free radicals
111
Electrically charged, highly reactive parts of molecules released during combustion
Free radicals
112
Extinguishment of a fire by interruption of the chemical chain reaction. (Dry chemical, Halon, etc)
Chemical flame inhibition
113
Compartment fire development depends on whether the fire is __ __ or __ __
Fuel limited
Vent limited
114
All compartment fires begin in the incipient stage as __ __ fires
Fuel limited
115
4 stages of fire development
Incipient
Growth
Fully developed
Decay
116
Description of a fire burning in the open with no restrictions to its oxygen supply
Open burning (free burning)
117
Transition from the incipient to the growth stage can occur in a matter of __ depending on the type and configuration of __
Seconds
Fuel
118
Horizontal movement of a layer of hot gases and combustion by-products from the center point of the plume
Ceiling jet
119
The drawing in and transporting of solid particles or gases by the flow of liquid
Entrainment
120
A fire the enters vent limited decay __ __ indicate that the fire is in its final stage of development
Does not
121
The __ of a fire in a compartment influences the entrainment of air into the fire
Location
122
Area surrounding a heat source in which there is sufficient air available to feed a fire
Combustion zone
123
__ __ is the tendency of gases to form into layers according to temp, gas density, and pressure
Thermal layering
124
Changes in ventilation and flow path can significantly alter..
Thermal layering
125
__ or __ flames may move through the hot gas layer
Isolated
Intermittent
126
The appearance of isolated flames is sometimes an immediate indicator of ..
Flashover
127
The interface between the hot gas layers and cooler layer of air is commonly referred to as the __ __ because the net pressure is zero, or __ where the layers meet
Neutral plane
Neutral
128
Even if temps decrease, __ can continue where a large volume of flammable products of combustion can accumulate within the compartment. These gases are fuel that can ignite with new oxygen source.
Pyrolysis
129
Warning: even coordinated tactical vent increases the combustion rate in __ __ fire
Vent limited
130
Rapid transition from growth to fully developed stage
Flashover
131
Rapid fire development has been responsible for numerous ff..
Deaths and injuries
132
Instantaneous explosion or rapid burning of superheated gases that occurs when oxygen is introduced into an oxygen depleted confined space
Backdraft
133
Flashover typically occurs during the fires __ stage
Growth
134
As flashover occurs, the gas temps in the room reach __ or higher
1100*F
135
4 common elements of flashover:
-Transition in fire development-growth to fully developed
-Rapidity-flashover happens rapidly, in a matter of seconds
-Compartment-must be an enclosed space
-Pyrolysis of all exposed surfaces
136
The auto ignition temp of CO, the most abundant fuel gas created by most fires, is approx..
1100*F
137
When a fire is in __ __ decay, the intro of new oxygen can trigger flashover quickly
Vent limited
138
The available __ limits the peak heat release in a fuel limited, fully developed fire
Fuel
139
Warning: additional ventilation will cause an already __ fire to grow
Ventilated
140
It is not possible to make enough __ in a compartment to transition a fire from vent limited to fuel limited conditions
Openings
141
__ __ occurs when a structural member fails-usually because of exposure to heat- and introduces a new source of oxygen to the fire
Unplanned ventilation
142
Unplanned ventilation is often the result of:
Occupant action
Fire effects on bldg
Actions other than planned, systematic, and coordinated tactical ventilation
143
Warning: wind speeds as low as __ mph can create wind driven fire conditions
10
144
Caution: a __ __ can overpower the natural convective effect of a fire and drive the smoke and hot gases back into the bldg
Strong wind
145
FF’s can influence fire dynamics in a number of ways:
Temp reduction
Fuel removal
Oxygen exclusion/flow path control
Chemical flame inhibition
146
Form of gas ignition; the ignition of accumulated flammable products of combustion and air that are within their flammable range
Smoke explosion
147
The total quantity of combustible contents of a bldg, space, or fire area, including finish and trim
Fuel load
148
The orientation of fuels as well as their surface-to-mass ratio will also influence the __ and __ of fire spread
Rate
Intensity
149
__ __ coverings may add carbon fuel (wooden siding) or petroleum fuels (vinyl siding) to the fuel load
Exterior wall
150
Thermal properties of a bldg include:
Insulation
Heat reflectivity
Retention
151
Unprotected engineered steel and wooden trusses can fail after __ to __ minutes of exposure to fire
5
10
152
For steel trusses, __ is the critical temp of steel- the temp at which steel begins to weaken
1000*F
153
Warning: entire pieces of decking may fall into the fire when __ __ fail. There may be no indications from the exterior that the trusses no longer support the roof decking.
Lightweight trusses
154
The bowstring truss’ compressional forces within the top chord act to force the load bearing walls __ as well as __
Outward
Downward
155
Web members in the bowstring truss transfer __ from the bottom chord and __ from the top chord onto load bearing walls
Tension
Compression
