Ch. 1 Fire Dynamics Flashcards
Ch. 1 pg. 13
The rate at which a fuel releases energy over time depends on many variables including: (4)
Chemical composition
Arrangement
Density of the fuel
Availability of oxygen for combustion
Ch. 1
The rate at which heat transfers is related to the _____________ of the bodies and the _____________ of the materials involved.
Temperature differential
Thermal conductivity
Note: The greater the temperature differences between the bodies, the greater the transfer rate.
Ch. 1 Conduction
Conduction is the transfer of heat through and between solids. Conduction occurs when a material is heated as a result of direct contact with a heat source. Heat transfer due to conduction is dependent upon three factors:
- Area being heated
- Temperature differences between the heat source and the material being heated
- Thermal conductivity of the heated material.
Ch. 1
The British Thermal Unit is the amount of heat required to raise the temperature of ________ of water by _______ Fahrenheit.
1 lbs.
1 degree
Ch. 1. Convection
Convection is the transfer of thermal energy by the circulation of movement of a fluid (liquid or gas).
Heat transfer due to convection is dependent upon three factors.
- Area being heated
- Temperature difference between the hot fluid or gas and the material being heated.
- Turbulence and velocity of moving gases
Ch. 1. Fuel pg 30
Fuel is the oxidized or burned material or substance in the combustion process. Most fuels are organic, containing carbon and other elements. Organic fuels can be divided into hydro-carbon based fuels, such as: (4)
- gasoline
- fuel oil
- Plastics
- Cellulose-based materials (wood and paper)
Ch. 1 fire dynamics: Solids
The _______ and ______ of a solid fuel relative to the source of heat also affects the way the fuel burns.
proximity
orientation
Ch. 1. fire dynamics; Oxygen
Oxygen in the air is the primary _______ agent in most fires.
oxidizing
the energy release in fire is directly proportional to the amount of oxygen available for combustion.
Ch. 1 Fire dynamics: Thermal Layering
________ is defined as the space between the air intake and the exhaust outlet.
Flow Path
Changes in ventilation and flow path can significantly alter thermal layering.
Ch. 1. fire dynamics: Flow Path
A flow path’s effectiveness to transport ambient air to the seat of the fire is based on the following: (4)
> size of ventilation opening
Length of the path traveled
Number of obstructions
Elevation differences between the base of the fire and the opening.
Ch. 1 fire dynamics: Unplanned ventilation
The source of new oxygen does not have to __________ from outside the building. When floors fail above basement fires, the interior air in the structure becomes a new oxygen source.
originate
Ch. 1 fire dynamics: Modern vs legacy
In single-family residential structures, the square footage of houses increased __________ between _____ and _____.
150%
1973
2008
Ch.1 Fire Dynamics
Fires can take various forms, but ____ fires, involve a chemical reaction between some type of ___ and ____, most commonly air.
All
Fuel and Oxidizer
______ are not combustible but will support or enhance combustion
Oxidizers
Ch. 1 pg.10
The study of matter and energy and includes chemistry and physics.
Physical Science
______ Can undergo many types of physical and chemical change
Matter
Occurs when a substance remains chemically the same but changes in size,shape and appearance
water freezing and liquid boiling are examples
Physical Change
When a substance changes from 1 type of matter into another.
Example: 2 or more substances combining to form compounds
Chemical Reaction
Chemical reaction involving the combination of an oxidizer
Oxidation
Occurs when a a force is applied to an object over a distance or when a substance undergoes a chemical,biological or physical change, this describes what?
Work
Amount of energy that and object can release at some point
potential energy.
Energy a moving object possesses
kinetic energy
Fuels have a certain amount of potential energy before they are ignited based on their____.
Chemical Composition
Rate at which a fuel releases energy over time depends on: (4)
- chemical composition
- Arrangement
- Density of fuel
- Availability of oxygen for combustion
Types of energy(7)
chemical thermal mechanical electrical light nuclear sound
In terms of ___ the potential chemical energy of a fuel converts into heat and light during combustion
Fire behavior
Energy is measured in?
Joules
In the customary system, the unit of measurement for heat is the….
British Thermal Unit (BTU)
1 pound water increased 1 degree fahrenheit
Reactions that emit energy as they occur
Exothermic Reactions
Fire is an exothermic reaction that releases energy in the form of __ and ___
Heat and Sometimes Light
Reactions that absorb energy
Endothermic Reaction
Example: water going from a liquid to a gas.
Fire Triangle Components (3)
Fuel
Oxygen
Heat
Fire Tetrahedron Components (4)
Fuel
Oxygen
Heat
Self sustaining chemical reaction
The fire tetrahedron model includes the Chemical Chain Reaction to explain ____ or _____ phase combustion
Flaming or Gas
An _____ chemical chain reaction must also be present for a fire to occur.
Uninhibited
Fuels must be in a ___ state to burn
Gaseous
When heat is transferred to a liquid or a solid the ___ increases and the substance converts to a gaseous state, also called ______
Temperature
Off-gassing
Temperature is the measurement of heat.
In ____, Off-gassing is a chemical change known as pyrolysis
Solids
Pyrolysis is off gassing of solids
Vaporization is off gassing of liquids
In___ a physical change is called vaporization
Liquids
Occurs when a mixture of fuel and oxygen encounter an external heat source with sufficient heat or thermal energy to start the combustion reaction
Piloted Ignition
Note: most common form of ignition
Occurs without and external flame or spark to ignite the fuel gases or vapors.
Autoignition
Exchange of energy from the burning gases to the fuel results in….
Sustained Combustion Reaction
The minimum temp at which a fuel in the air must be heated in order to start self sustained combustion
Autoignition Temp
Combustion is a____ and can occur without flames
chemical reaction
Occurs when a gaseous fuel mixes with oxygen in the correct ratio and heats to ignition temp
Flaming combustion
fire commonly know as flaming combustion
Each element of the Fire Tetrahedron must be in proper proportion and in close physical proximity for ____ combustion to occur
Flaming
Ignition is where the ____ process begins
Combustion
As the heat transfers to the gaseous combustion process, they begin to expand and begin to rise and move away from the fire due to_____
Buoyancy
note: think smoke and convection
Products of combustion are simply described as ____ and ____.
Heat and Smoke
pg 18
Exposure to toxic gases found in smoke and ______ cause most fire deaths
Lack of oxygen
Smoke is the product of _____ combustion.
Incomplete
ch. 1 pg. 18
as fuel burns, its chemical composition changes, creating new products. THese products are simply discribed as heat and smoke. smoke is an aerosol comprised of ____, _____ and _____________
gasses,
vapors
solid particulates
Most structure fires involve multiple types of ___ and limited____
Fuels
Limited Air Supply
When air supply is ____, incomplete combustion is higher, which produces more smoke.
Limited
Vapor and Particulates give smoke its varied_____
Colors
As part of the chemical reaction, the consumed oxygen combines with carbon in the smoke to form combustion products like…..
Carbon Monoxide
Carbon Dioxide
Concentration of the products of combustion and low oxygen concentration can cause____
Asphyxiation (fatal level of oxygen deficiency in blood)
pg 19
Frequently identified as the cause of death in civilian fatalities
CO Exposure
pg 19
Sometimes lethal condition in which carbon molecules attach to hemoglobin, decreasing bloods ability to carry oxygen
CO Poisoning
pg 19
CO combines with hemoglobin ____ times more effectively than oxygen does
200
pg 19
Does not act on the body, but excludes oxygen from the blood leading to hypoxia of the brain and tissues
Carbon Monoxide
A toxic flammable substance produced in combustion of materials containing Nitrogen commonly found in smoke although at lower levels than CO
Hydrogen Cyanide (HCN)
Ch. 1. Flow Path.
The flow path is composed of two regions: the ambient air flow in and the hot exhaust flow out. The flow is alway unidirectional due to pressure with ambient air moving _____ and the products of combustion flow______ from the fire towards low pressure outlet.
toward the fire.
away
35 times more toxic than CO.
Prevents body from using oxygen at the cellular level.
Can be inhaled, ingested, or absorbed where it then targets the heart and brain
HCN
Product of complete combustion of organic materials. Displaces oxygen creating oxygen deficient atmosphere.
Acts as respiratory stimulant, increasing respiratory rate.
Carbon Dioxide (co2)
At Standard Temp (68 degree F) and Atmospheric Pressure (1) gases remain calm. Differences above or below this pressure create?
(as little as 0.1kPa or less)
Movement in gases.
pg 22
Heat is the __kinetic energy needed to release the potential energy in a fuel, While_____ is the measurement of Heat.
Thermal
Temperature
pg 22
Chemical, electrical and mechanical are all sources of___Energy and most frequently the ignition sources of structure fires.
Thermal Energy
ch. 1 pg 22
A form of oxidation and a Chemical reaction that increases the temperature of a material without the addition of external heat which can lead to spontaneous combustion.
Self Heating
ch 1 pg. 12
Normally produces thermal energy slowly but and external heat source, such as the sun, can accelerate the process.
Oxidation
pg. 24
Electric current flowing through a conductor produces Heat. When a current flowing through a conductor exceeds its design limits,the conductor may over heat and present and ignition hazard.This is an example of?
Unintended Resistance Heating
note: this is over current or overload.
pg 24
High temp luminous electric discharge across a gap or through a medium is referred to as_____. Which is different than ____, which are luminous glowing particles from electric arc that splatter away from the point of arcing.
Arcing
Sparking
pg 24
Diesel engines use ____ energy which generates heat when a gas is compressed. When a compressed gas expands, it absorbs heat.
Mechanical Energy
Friction or compression generates mechanical energy.
pg 26
The rate at which heat transfers is related to the temperature differential of the bodies and the _____ conductivity of the materials involved.
Thermal
pg 26
____ is the transfer of heat through and between solids occurs when a material is heated as a result of direct contact with a heat source and increases molecular motion and collisions between a substances molecules.
Conduction
The transfer of thermal energy by the the circulation or movement of a fluid(liquid or gas) is called____ ? In the fire environment, this usually involves the transfer of heat through the movement of hot smoke and fire gases.
Convection
Convection may occur in any direction. Vertical movement is due to_____ while horizontal movement is usually the result of_____ differences.
Buoyancy
Pressure
___ heat can become the dominant mode of heat transfer as the fire grows in size and can have significant effects on the ignition of objects some distance from the fire resulting in fire development and spread in compartments.
Radiant
Radiant heat transfer primarily depends on the __ of the heat source. As an electromagnetic wave, radiated heat energy travels in a ______ at the speed of sound.
Temperature
Straight Line
Radiated heat travels through ____ and air spaces that would normally disrupt conduction or convection. However,materials that reflect, absorb or scatter radiated energy will ____ the heat transmission.
vacuums
disrupt
pg 28 Situational awareness (in the moment) is essential for monitoring PPE performance during operations. This is especially true when SCBA facepieces are susceptible to radiated\_\_\_\_\_ . This heat emitted from flames or hot surfaces may cause PPE failure even when temp of gasses within a compartment are within acceptable limits.
Heat Flux (kw/m2)
ch.1 pg. 30
____ may be found in any of the 3 states of matter and is the oxidized or burned material or substance in the combustion process known as the reducing agent.
Fuel
Organic fuels such as plastics and cellulose are ____ based, while inorganic fuels do not contain_____.
Carbon
Carbon
The rate at which energy transfers and rate at which energy converts from one form to another is known a___ which is measured in watts. 1 watt=1___ per second.
Power
Joule
The heat release rate refers to the ___ released per unit of time and is measured in ____watts or ____watts.
energy
kilo=thousand
Mega=million
Vapor density describes the density of ____ in relation to air and is measured at standard temp and pressure. Air has a vapor density of 1 which means gasses greater than 1 will____ while gasses less than 1 will___.
gasses
sink
rise
For vaporization to occur, the escaping vapors must be at a ___ pressure than the atmospheric pressure. The pressure that vapors escaping from a liquid exert is ____ pressure. Flammable liquids with a high vapor pressure present a special hazard to Firefighters.
greater
vapor
___ have mass but no definite shape. ____ gravity is the ratio of mass of a given volume of liquid compared to the mass of an equal volume of water at the same temp
Liquids
Specific
___ point is the minimum temp a liquid gives off sufficient vapors to ignite but not sustain combustion in the presence of a piloted ignition source. However, the temp at which a piloted ignition of sufficient vapors will begin a sustained combustion process is called the ____point.
Extra: Liquid fuels that vaporize sufficiently to burn under___ present a significant flammability hazard.
Flash
Fire
100 degrees F
- Describes extent to which a substance will mix with water.
- Materials that are___ will mix with water in any proportion.
- Flammable liquids known as___ will mix with water.
- Solubility
- Miscible
- Polar solvents
- FF’s should use proper __or __ agent to extinguish liquid fuels that are not water soluble.
- Water soluble liquids will mix with some water-based extinguishing agents, such as many types of ___ ____ foam.
- Should use Alcohol resistant firefighting foams specifically designed for ___ ___.
- Foam or chemical
- Fire fighting
- Polar Solvents
Solid fuels have definite shape and size that can significantly affect how easily they ignite. Wood, when it first heats, begins to ___ and decompose into its volatile components and carbon. This process can begin at temps below ____ in wood.
Pyrolize
400 degrees F
The ___ and ___ of a solid fuel relative to the source of heat affects the way a fuel burns.
Proximity
Orientation
Oxygen in the air(which consists of 21% oxygen) is the ____ oxidizing agent in most fires, In most compartment fires, the energy released is directly proportional to the ____amount of oxygen available, not the amount of fuel. At normal ambient temp (68*F) materials can ignite and burn at oxygen concentrations as low as____%.
Primary
Limited
15%
Oxygen Deficient %
Oxygen Enriched %
Oxygen Enriched % that Nomex burns
Note:Fires in Oxygen enriched atmospheres are more difficult to extinguish and present potential safety hazard.
19.5%
23.5%
Approx 31%
The range of concentrations of the fuel vapor and air is called_____ range. This is reported using the percent of gas or vapor in air for the ___ and ____.
Flammable(explosive)
LEL(Min. concentration of fuel vapor and air that supports combustion)
UEL(Concentration above which combustion cannot take place)
ch 1 pg. 25
Thermal dynamics is the study of heat transfer. The rate at which heat transfers i related to two properties of the material:
1
2.
- temperature differential of the bodies
2. thermal conductivity of materials involved.
