Ch. 1 Fire Dynamics Flashcards by Dave Weaver

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

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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.

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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.

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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

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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

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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)

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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

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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.

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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.

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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.

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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

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Ch. 1 fire dynamics: Modern vs legacy

In single-family residential structures, the square footage of houses increased __________ between _____ and _____.

150%
1973
2008

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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

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______ are not combustible but will support or enhance combustion

Oxidizers

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Ch. 1 pg.10

The study of matter and energy and includes chemistry and physics.

Physical Science

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______ Can undergo many types of physical and chemical change

Matter

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Occurs when a substance remains chemically the same but changes in size,shape and appearance
water freezing and liquid boiling are examples

Physical Change

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When a substance changes from 1 type of matter into another.

Example: 2 or more substances combining to form compounds

Chemical Reaction

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Chemical reaction involving the combination of an oxidizer

Oxidation

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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

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Amount of energy that and object can release at some point

potential energy.

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Energy a moving object possesses

kinetic energy

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Fuels have a certain amount of potential energy before they are ignited based on their____.

Chemical Composition

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Rate at which a fuel releases energy over time depends on: (4)

chemical composition
Arrangement
Density of fuel
Availability of oxygen for combustion

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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

1. Describes extent to which a substance will mix with water. 2. Materials that are___ will mix with water in any proportion. 3. Flammable liquids known as___ will mix with water.

1. Solubility 2. Miscible 3. Polar solvents

1. FF's should use proper __or __ agent to extinguish liquid fuels that are not water soluble. 2. Water soluble liquids will mix with some water-based extinguishing agents, such as many types of ___ ____ foam. 3. Should use Alcohol resistant firefighting foams specifically designed for ___ ___.

1. Foam or chemical 2. Fire fighting 3. 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.

1. temperature differential of the bodies | 2. thermal conductivity of materials involved.