3 Fire Behavior Flashcards
The science of fire is an attempt to understand and control fire and involves both scientific and commonsense answers to the following questions
How does fire transform matter. How does fire spread
When material burns a visible change occurs, generating what
Heat and light
What occurs when a material or substance remains chemically the same but changes in size shape or appearance
A physical change
What occurs when a substance changes from one type of matter into another.
Chemical change
Reactions that absorb energy as they occur are called
Endothermic
Reactions that give off energy as they occur are called
Exothermic
Fire is what
And exothermic chemical reaction called combustion that releases energy in the form of heat and light
If your potential energy is released during combustion and converted into what
Kinetic Energy
Some solid fuels particularly those that are porous can char and undergo oxidation on the fuel surface. This oxidation is known as
Nonflaming or smoldering combustion
The old combustion model composing of oxygen fuel and heat
Fire triangle
The new fire behavior model which explains smoldering combustion comprising of heat fuel or reducing agent chemical change reaction and oxidizing agent
Fire tetrahedron
The fire tetrahedron is comprised of four elements
Fuel. Auction. Heat. Self sustained chemical reaction
The material or substance being oxidized or burned in the combustion process
Fuel, reducing agent
In organic fuels such as hydrogen or magnesium do not contain what
Carbon
Organic fuels contain what
Carbon
Organic fuel can be for the divided into two categories
Hydrocarbon-based, cellulose based
To key factors influencing the combustion process are
Physical state and its distribution or orientation
Three physical states of matter which fuel may be found
Solid liquid or gas
For flaming combustion to occur fuels must be in what state
Gaseous
A fuel that has definite size and shape
Solid fuel
A type of plastic that is not readily change its physical shape when exposed to heat
Thermosetting plastics
When wood is first heated what is released as the wood dries
Water vapor
As surface increases the more material is exposed to heat in this generates combustible pyrolysis products more quickly making the fuel easier to ignite is the explanation of what
Surface to mass ratio
The distribution and orientation of a solid fuel, vertical/horizontal, relative to the source of heat also affects what
The way it burns
A state of fuel that has mass and volume but no definite shape
Liquid fuel
Gasoline has a specific gravity of what
Less than one
Liquid fuels have a number of characteristics that contribute to their abilities to ignite and burn. These characteristics include the following
Solubility. Vaporization. Vapor pressure. Flashpoint. Flammable/combustible liquids. Surface area
Flammable liquids have a flashpoint that is less than what temperature
Less than 100°F
Combustible liquids have a flashpoint that are greater than what temperature
Greater than 100°F
Transformation of a liquid to a vapor or gaseous state
Vaporization
Pressure produced or exerted by the vapor that a liquid releases. As a liquid is heated this increases along with the rate of vaporization
Vapor pressure
The temperature at which a liquid releases sufficient vapors to ignite but not sustain combustion, commonly indicate flammability hazard of liquid fuels
Flashpoint
Extent to which a substance will mix with water
Solubility
Substances that readily mix with water such as alcohol
Polar solvents
Materials that are miscible in water will mix in
Any proportion
Weight of a given volume of pure vapor or gas compared to the weight of an equal volume of dry air at the same temperature and pressure
Vapor density
The most dangerous type of all fuel types
Gaseous fuel
State of fuel that mass but no definitive shape or volume
Gaseous fuel
A gas that has a vapor density less than one and rises
Methane
Liquid petroleum gas tends to sink and has a vapor density less or greater than one
Greater than one
Vapor density is generally specified at what temperature
68°F
The primary oxidizing agent in most fires is what
Oxygen
At normal ambient temperatures materials can ignite and burn at oxygen concentrations as low as what percent
14%
Some petroleum-based materials will auto ignite during what condition
Oxygen concentrations are higher than 21%
And industrial bleaching agent used to typically for paper manufacturing
Hydrogen peroxide
many materials that do not burn at normal oxygen levels and burn readily and what type Of atmosphere
Oxygen enriched
The fuel to air concentration range that supports combustion is called
The flammable range. Or explosive range
Lowest Limit at which a flammable gas or vapor will ignite
Lel
Upper limit at which flammable gas or vapor will ignite
UFL
True/false. Variations in temperature and pressure can cause the flammable range to vary considerably
True
Generally increases in temperature or pressure brought in the range of
Flammability
Decreases in temperature and pressure does not narrow the flammable range. True/false
False it does narrow it
Energy exists in two states
Potential and kinetic energy
Potential energy is
The energy possessed by an object that may be released in the future
The energy possessed by a moving object is
Kinetic energy
Form of energy associated with the motion of atoms or molecules and capable of being transmitted through solid and fluid media by conduction convection and radiation
Heat
Heat moves away from fuel that is burning toward what
Fuel that is not burning
Flammable Range of methane
5% through 15%
Flammable range of propane
2.1% -9.5%
Flammable range of carbon monoxide
12% -75%
Flammable range of gasoline
1.4% -7.4%
Flammable range of diesel
1.3% -6%
Flammable range of ethanol
3.3% -19%
Flammable range of methanol
6% -35.5%
There are two forms of ignition
Piloted ignition and autoignition
This type of ignition occurs when a mixture of fuel and oxygen encounters and external heat source with sufficient heat energy to start the combustion reaction
Piloted ignition
This type of ignition occurs without any external flame or spark to ignite fuel gases or vapors
Autoignition
Temperature to which the service of a substance must be heated for ignition and self sustained combustion to occur
Autoignition temperature
The autoignition temperature is always higher than what
The pilot ignition temperature
The most common type of ignition is
Piloted ignition
Heat energy usually comes from one or more of the following sources
Chemical. Mechanical. Electrical. Light. Nuclear. Sound
The most common sources of heat that results in the ignition of fuel
Chemical and electrical and mechanical energy
The most common source of heat in combustion reactions
Chemical heat energy
Oxidation almost always results in the production of what
Heat
Heating that occurs when a material increases in temperature without the addition of external heat
Self heating, or spontaneous heating
For spontaneous ignition to occur the following set of circumstances must be met
Insulate of property of material must be so that it cannot dissipate as fast as it is being generated.
Rate of the production great enough to raise temperature to ignition point.
Available air supply adequate to support combustion
Heat generated as electrical current passes through a conductor such as copper wire
Electrical heat energy
Electrical heating can occur in several ways including the following
Resistance heating.
Overcurrent or overload.
Arcing.
Sparking
Heat produced when electric current flows through a conductor
Resistance heating
Unintended resistance heating
Overcurrent or overload
High temperature luminesce electric discharge across a gap or through a medium such as charted insulation
Arcing
Form of heat energy generated by friction or compression
Mechanical heat energy
Movement that results in the generation of heat and or Sparks, created went to services move against each other
Heat of friction
Energy created when a gas is compressed
Heat of compression
In order for heats to be transferred from one object to another the two objects must be a different
Temperatures
The transfer of heat from object to object is measured as
Energy flow overtime
Transfer of heat within an object or to another object by direct contact, heat flow through and between solids
Conduction
The transfer of heat energy for my fluid, liquid or gas, to a solid surface
Convection
Transmission of energy as an electromagnetic wave such as lightwaves radio waves are x-rays without an intervening medium
Radiation
All matter having a temperature above what will radiate heat energy
Absolute zero
This type of he becomes the dominant Mode of heat transfer when a fire grows in size and he can have significant effect on the ignition of objects located some distance away
Radiant heat
A wide range of factors influence radiant heat transfer including the following
Distance from heat source.
Temperature difference between source and material heated.
Collar and reflective qualities of heat source and material heated
As temperature of the heat source increases the radiant energy increases by a factor of what
Increases by a factor to the fourth power
Materials that absorbs heat but do not participate actively in the combustion reaction
Passive agents
A passive agent that slows the absorption of heat energy in the ignition and combustion process
Fuel moisture
Insulating materials retard the transfer of heat primarily by what
Slowing conduction from one body to another
Type of heat transfer that is the cause of most exposure fires
Radiation
A fourth method for heat transfer that has historically been used by the fire service is actually a combination of conduction and radiation rather than an independent method of heat transfer
Direct flame contact
Free radicals combined with oxygen or with the elements that form the fuel material producing what
Intermediate combustion products, new substances
Free radicals
Atom or group of atoms that has at least one unpaired electron, unstable and reactive
Methane burns it creates what
Carbon and hydrogen
When methane burns it creates what
Carbon monoxide and formaldehyde
Surface combustion also involves oxidation at the surface of the actual material without initiation or continuation of the chemical change reaction found in what type of combustion
Flaming combustion
Surface or smoldering combustion cannot be extinguished by chemical inhibition because
There are no flames and related chemical change reaction
Halon agents extinguish fires by
Interrupting the chemical chain reaction
An aerosol comprised of fire gases paper and solid particles
Smoke
Carbon monoxide is the byproduct of
Incomplete combustion of organic materials
Most common products of combustion encountered in structure fires
Carbon monoxide
This is Produced in The combustion of materials containing nitrogen and a significant byproduct of the combustion of polyurethane foam
Hydrogen cyanide
Product of complete combustion of organic materials is non-toxic but is an asphyxiant by displacing oxygen
Carbon dioxide
This class of fire involves ordinary solid combustible materials such as would cloth paper rubber and plastics
Class a fires
This class of fire involves my flammable and combustible liquids and gases such as gasoline oil and alcohol
Class B fires
Class c fires involve what
Energize electrical equipment
Combustible metals such as aluminum magnesium potassium sodium titanium and zirconium form this class of fire
Class D
True/false. No single extinguishing agent effectively controls fires and all combustible metals
True
Class K fires involve
Oils and greases normally found in commercial kitchens using deep fryer’s
A process caused by class K extinguishing agents turning fats and oils into a soapy foam that extinguishes a fire
Saponification
When sufficient oxygen is available for development is controlled by the characteristics and configuration of the fuel and is considered to be
Fuel controlled
When fire development is limited by the air supply the fire is set to be
Ventilation controlled
Four stages of fire development
Incipient. Growth. Fully developed. Decay
Ignition occurs when all three elements of the fire triangle come together and combustion happens true or false
true
Once combustion begins development of an incipient fire is largely dependent on the characteristics and configuration of
Fuel involved
To draw in and transport as solid particles or gas, by the flow of a fluid
Entrain
The ceiling Jet is otherwise known as
Mushrooming
First affect caused by the transition into the growth stage is the amount of air that is
Drawn into the plume
What determines the amount of air that is entrained and thus the amount of cooling that takes place
Location of fuel in relation to the compartment walls
Thermal layering, isolated flames, rollover, and flashover are all found during what stage of fire
Growth stage
Pocket flames that may be observed moving through the hot gas layer above the neutral plane is sometimes referred to as
Ghosting
The rapid transition between the girls and fully developed by her stages but not a specific event like ignition
Flashover
When the temperature in a compartment results in the simultaneous ignition of all the combustible contents in the space
Flashover
Flashover temperature is typically occur between what
Between 900°F and 1200°F
The temperatures associate with flashover is a range that usually correlates with the autoignition temperature of what, commonly produced gas
Carbon monoxide
To develop flashover conditions the fuel must have sufficient
Heat energy
A seal room might not provide enough what for a developing fire to reach flashover
Ventilation, oxygen
Measurement of the amount of heat released when a material burns as stated in kilowatts or BTU
Heat release rate
Most fires they grow beyond incipient stage become what controlled
Ventilation controlled
The compartment fire will Decay as the fuel is consumed or as the oxygen concentration
Falls to the point where Flaming combustion can no longer be supported
Instantaneous explosion or rapid burning of superheated gases that occurs when oxygen is introduced into a smoldering fire in a confined space
Backdraft
Flammable products of combustion can accumulate within the compartment and if with in the flammable range they can ignite resulting in
Smoke explosion
Ignition of accumulated flammable products of combustion
Smoke explosion
A Backdraft will occur if the accumulated products of combustion are at or above their
Ignition temperature
The following factors influence fire development with in a compartment
Fuel type. Availability and location of additional fuel. Compartment volume. Ventilation. Thermal properties of compartment. Ambient conditions. Effects of changing conditions.
In a compartment fire the most fundamental fuel characteristics influencing fire development are
Mass and surface area
A number of factors influence the availability and location of additional fuels including the following
Building configuration. Contents of building. Construction of the building. Interior finish materials. Fuel proximity and continuity. Fire location
Amount of fuel present express quantitatively in terms of weight of fuel per unit area
Fuel load
All things being equal a fire and a large compartment will develop more slowly than one in
A small compartment due to greater volume of air and material that must be heated
Firefighters influence our behavior by doing one or more of the following actions
Reducing temperature. Eliminating fuel. Separating the fire from available fuel. Changing oxygen concentration. Interrupting chemical chain reaction
When water is converted into steam at 212°F expands approximately how many times
1700 times
Simplest method of fuel removal is
To allow the fire to burn until all fuel is consumed
For fires involving pesticides or flammable liquid spills what might be the most appropriate action to extinguish
Allowing fuel to burn out because of possible environmental harm from water run off
Example of oxygen exclusion to extinguish fire would be
Covering a cooking fire pan with a lid. Dry chemical extinguisher
Halogenated agents are effective in extinguishing gas and liquid fuels because
They interrupt chemical change reaction and the fuels must flame to burn
The primary duty of the fire inspector is to ensure
The life safety of all citizens and fire emergency services responders
