Chapter 13: Fire Behavior

Question 1

2 types of Ignition

Answer 1

Piloted: the moment when a mixture of Fuel & O2 encounter an external heat source with sufficient thermal energy to start the combustion reaction

Auto Ignition: is the initiation of combustion with out spark or flame to ignite gases or vapor

Question 2

Modes of Combustion

Answer 2

Flaming: occurs when gaseous fuel mixes with O2 in the correct ratio and heated to the ignition temp.

Non-Flaming: Occurs more slowly and at lower temperature producing a smoldering glow in the materials surface

Question 3

3 forms of Energy

Answer 3

Mechanical: Adiabatic Compression, Friction, Friction Sparks

Electrical: Resistance Heating, Over-current/Overload, Arching, Sparking

Chemical: Self-Heating, Spontaneous Ignition

Question 4

LAW OF HEAT FLOW

Heat transfer

Answer 4

heat is like pressure it will go from areas high temp to areas of lower temp
heat energy can be transferd in 4 ways
-Conduction: transfer of heat between solids

• Convection: TRANSFER OF THERMAL ENERGY BY THE CIRCULATION/MOVEMENT OF FLUID/GAS
• Radiation: TRANSFER OF THERMAL ENERGY as an electromagnetic wave without an intervening medium… light,radio,Xray. Factors that influence: Nature of exposed surfaces, distance between heat source and exp. surface, Temp diff. between heat source and exp surface
• Direct Flame Contact

Question 5

Fuel

Answer 5

Fuel is the reducing agent

Question 6

4 stages of fire development

Answer 6

Incipient
Growth
Fully Developed
Decay

Question 7

3 types of rapid Fire Development

Answer 7

Smoke Explosion
Back Draft
Flash Over

Question 8

Matter

Answer 8

Anything that occupies space and has mass.
Solid
Liquid
Gas(only gases will burn)

Question 9

Physical vs Chemical Change

Answer 9

Physical: substance remains chemical the same but changes shape, size, appearance (state liquid to gas)

Chemical Change: Change from one type of matte to another like 2 types of matter are combined to form a substance

Question 10

Energy

Answer 10

capacity to preform work

Question 11

Potential & Kinetic energy

Answer 11

Potential: the amount of kinetic energy a an object can release in the future

Kinetic: energy possessed by a moving object

Question 12

Law of Conservation of Mass

Answer 12

Mass and Energy my be converted from one to an other, but there is never any net loss of total mass/energy

Question 13

Chemical reactions that release thermal energy

Answer 13

Exothermic

Question 14

Chemical Reactions that absorb thermal energy

Answer 14

Endothermic

Question 15

Pyrolysis & Vaporization

Answer 15

Pyrolysis: Chemical decomposition of a solid material by heating. = gases that burn

Vaporization: Physical process that changes a liquid to gaseous state

Question 16

Auto Ignition Temerature

Answer 16

The lowest Temperature which a combustible material will ignite without an external source of ignition

Question 17

Fire

Answer 17

Is a rapid oxidation process, which s chemical reaction resulting in the evolution of light and heat in varying intensities

Question 18

Combustion

Answer 18

is defined as a chemical process of oxidation that occurs at a rate fast enough to produce heat and usually light in the form of either glow or flame

Question 19

Products of combustion

Answer 19

Heat light and Smoke

Question 20

Smoke

Answer 20

SMOKE: Suspension of heated gases and small visible particles of liquids and solids such as steam, carbon, tars and dust in air a resulting from the incomplete combustion of a fuel

• Is an Aerosol comprised of Gases, Vapor, and Solid Particulates.

smoke is a product of of incomplete combustion
Carbon Monoxide, Hydrogen Cyanide, Carbon Dioxide, Irritants

Question 21

Flame

Answer 21

Is the visible, luminous body of a burning gas

with proper amounts of O2 the flame becomes hotter and less luminous because of a more complete combustion

Question 22

Fire Triangle

Answer 22

Elements/Conditions needed for COMBUSTION
Fuel
Oxygen
Heat

Question 23

Fire Tetrahedron

Answer 23

4 elements/conditions required to have FIRE
Heat
Fuel
Oxygen
Chemical Chain Reaction

Question 24

HEAT

Answer 24

Heat is Kinetic Thermal Energy transferred from a high temp. substance to a low temp. substance

it is always in transit from open flame to exposed fuel

Question 25

Temperature

Answer 25

is the measurement of heat

Question 26

Chemical Energy: self heating

Answer 26

A form of oxidation, is a chemical reaction that increases the temperature of a material without the addition of external heat

Question 27

Chemical Energy: Spontaneous Ignition

Answer 27

Initiation of combustion of a material by an internal chemical/biological reaction that has produced sufficient heat to ignite material

if heat cannot escape fast enough it will accumulate to the point where spontaneous ignition may occur

Question 28

Mechanical Energy: Adiabatic Compression

Answer 28

Is the generation of heat when a gas is compressed

Question 29

Fuel(reducing agent)

Answer 29

A fuel is a substance being oxidized in the combustion process.

fuel can be solid, liquid, gas; but must be in a gaseous state to burn

Question 30

Heat of combustion and Heat Release Rate

Answer 30

Heat of combustion: is the total amount of thermal energy that could be generated by the combustion reaction if the fuel were completely burned.

Heat Release Rate: is the total amount of Heat released per unit of time and measured in kW

Question 31

Specific Gravity

Answer 31

Ratio of MASS of a given volume of liquid compared with the MASS of equal volume of water

Question 32

Vapor Pressure

Answer 32

the pressure of vapors escaping from a liquid;

flammable liquids with a high vapor pressure present a special hazard for ff; this is an indication of how easily they will evaporate

Question 33

Flash Point

Answer 33

is the minimum temperature at which a liquid gives off sufficient vapors to ignite but not sustain combustion

Question 34

Fire Point

Answer 34

is the temperature at which sufficient vapors are being generated to sustain the combustion reaction

under 38’c/100’f flammability hazard

Question 35

Solubility

Answer 35

Describes the extent to which a substance will mix with water

Question 36

materials that will mix in any proportion with water are

Answer 36

Miscible

Question 37

Polar Solvents

Answer 37

liquids that will readily mix with water

Question 38

Gases
all flues must be gaseous state to burn
A fuel has a LEL and UEL

Answer 38

LEL; Lower Explosive Limit: the lowest concentration of a combustible or flammable gas in the air that will support combustion
UEL; Upper Explosive Limit: Highest concentration of a combustible or flammable gas in the air that will support combustion

Question 39

Explosive Range or Ignitable mixture

Answer 39

The range of vapor mixture that will ignite when subjected to an ignition source

Question 40

Vapor Density

Answer 40

describes the density of gases in relation to air: air =1

Question 41

Oxidizing Agents

Answer 41

is any substance that yields oxygen during a chemical reaction. An oxidizer is not combustible but will support combustion

Question 42

Oxygen enriched

Oxygen Deficient

Answer 42

Normal 20-21%
Enriched>21%
Deficient<20%

Question 43

open fire strategy

Answer 43

cool the fire

Question 44

Compartment fire

Answer 44

Fuel Controlled: A fire with adequate oxygen in which the HRR and growth are determined by the characteristics of the fuel, such as quantity and geometry

Ventilation Controlled: A fire with limited ventilation in which the HRR or growth is limited by the amount of oxygen available to the fire

Question 45

Thermal Layering

Answer 45

Tendency of gases to form into layers according to temperature

Question 46

7 factors that affect fire development

Answer 46

• Fuel Type
• Avilablity and location of additional fuel
• Compartment volume and height of celing
• Ventilation/oxygen supply
• Thermal prperties of compartment
• Ambient weather conditions
• Fuel load

Question 47

Rapid Fire Development

Answer 47

Smoke explosion
Backdraft
Flashover

Question 48

Flashover

Answer 48

is a very rapid transition from local burn of contents with in a compartment to wide spread burning of all exposed fuels with in that compartment.

• can happen in as little as 90 sec.
• temp 650-1200’C
• CO has a flammable range of 12.5-74% , ignites at 610’C
• .5-2sec escape time @ 2.5’ per sec = 5’ max distance

Question 49

4 precursors to flashover

Answer 49

Free Burning
High Temp
Heavy Dark Smoke
Rollover

Question 50

4 Variables of flash over

Answer 50

• Compartment size
• Insulation qualities of compartment
• Ceiling height
• Ventilation: can delay(incepent,growth,) or cause(Fully developed/Decay) flash depending on stage of growth

Question 51

Backdraft

Answer 51

explosively rapid combustion of flammable gases caused by an increase in ventilation

introduction of O2 causes fire of explosive force

Question 52

5 Indicators of potential back draft

Answer 52

• Building:fire contained to single compartment
• Smoke: heavy dense smoke that moves or pulses
• Air flow:high velocity turbulantsmoke dischargeappering to breath/puff
• Heat: high heat, smoke stained windows, walls are hot to the touch
• Flame:little or no visible flame

Question 53

Smoke Explosion

Answer 53

It is the ignition of a premixed pocket of fire gases and oxygen that may occur when an ignition source is introduced

• smoke color is not an indicator
• can involve cold smoke
• it involves a contained layer of flammable smoke already existing with in the flammable range
• all it requires is an ignition source