13 - Fire Behaviour

Question 1

Physical vs chemical change

Answer 1

Physical: reversable change where the chemical composition doesnt change.
Chemical: substance changes from one substance to another, such as compounds or combustion. Unreversible.

Question 2

Energy definition and types of energy

Answer 2

Energy is the capacity to perform work.
Potential: the amount of kinetic energy an object CAN release in the future.
Kinetic: energy possessed by a moving object.
Chemical, Electrical, Sound, Mechanical, thermal

Question 3

Exothermic vs endothermic

Answer 3

Exothermic release thermal energy; combustion.
Endothermic collects thermal energy; steam conversion.

Question 4

Pyrolysis

Answer 4

The chemical decomposition of a solid material by heating

Question 5

Vaporization

Answer 5

Physical process of changing a liquid into a gaseous state

Question 6

Forms of ignition

Answer 6

Piloted ignition: moment when a mix of fuel and O2 meet an external heat source with sufficiant thermal energy to start the combustion process.
Autoignition: Initialt of combustion by heat without spark or flame to ignite fuel gases or vapor.

Question 7

Fire definition (verbatim)

Answer 7

Fire is defined as a rapid oxidation process which is a chemical reaction resulting in the evolution of light and heat in varying intensities.

Question 8

Combustion definition (verbatim)

Answer 8

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

Question 9

Non-flaming vs Flaming combustion

Answer 9

Flaming: when a gaseous fuel mixes with O2 in the correct ration and is heated io ignition temp. Produces visible flame above the material.
Non-Flaming: slower at a lower temp, produces smoldering flow on the materials surface.

Question 10

Products of combustion

Answer 10

Heat: thermal energy and release.
Smoke: product of incomplete combustion. Highly toxic
Carbon monoxide: incomplete combustion of inorganic materials
Hydrogen Cyanide: combustion of materials containing nitrogen.
Carbon Dioxide: combustion of organic materials. Acts as an asphyxiant.
Irritants.
Flame:

Question 11

Fire triangle and tetrahedron

Answer 11

Triangle: Heat, O2, Fuel. Explains elements and conditions nessissary for combustion
Tetrahedron: Heat, O2, Fuel, chem chain reaction. Remove one of the 4 parts of the tetrahedron and combustion will not occur.

Question 12

3 sources and their subsources of THERMAL ENERGY

Answer 12

Chemical: Self heating, spontanious ignition.
Electrical: Resistance, overcurrant or overload, Arcing, Sparking.
Mechanical: Adiabatic compression, Friction, Friction Sparks

Question 13

3 heat transfer methods

Answer 13

Conduction: transfer of heat through direct contact of solids. [touching a hot surface]
Convection: heat transfer through movement of fluid (liquid or gas). [heat rises through smoke and air]
Radiation: transmission of energy as an electromagnetic wave (without the need of a medium such as air). [the actual flames or smoke radiate heat]

Question 14

factors effecting radiant heat transfer

Answer 14

Nature of exposed surfaces: darker rougher material emit and absorb heat much more effectively.
Distance between heat source and exposed surface.
Temperature difference between heat source and exposed surface.

Question 15

Pyrolysis definition

Answer 15

Chemical decomposition of a solid material by heating.

Question 16

Reducing agent definition

Answer 16

A fuel, that must be in its gaseous state to be burned.

Question 17

Heat of combustion

Answer 17

Total amount of thermal energy that could be generated by the combustion reation if a fuel were completely burned. (Mj/Kg)

Question 18

Heat release rate

Answer 18

Total amount of heat release per unit of time. (kW)

Question 19

Specific gravity

Answer 19

Ratio of mass of a given volume of a liquid compared with the mass of an equal amount of water at the same temperature. Water = 1.0

~~~everything below is just for clarification~~~
Ratio is #:Water or as a number. Water being 1.0. If #>1, its heavier=sinks. If #<1, its lighter=floats.

(so if you have 1 liter of water, which weighs 1kg, and 1L of mystery fluid, that weighs 1.5kg, the ratio is 1.5:1 (or just 1.5) meaning its heavier than water. Alternatively, if you have a liquid that weighs 0.5kg, the ratio is 0.5:1 (or just 0.5), weighing lighter than water, thus floating [like gasoline, ~0.79])

Sinks>Water(1.0)>Floats

Question 20

Vapor pressure, and what it indicates

Answer 20

Pressures that vapors escaping from a liquid exert. Indicates how easily a substance will evaporate. Higher VP indicates higher evaporation rate and volatility.

Question 21

Flashpoint definition

Answer 21

Flashpoint is the minimum temperature at which a liquid gives off enough vapors to form an ignitable mixture with air near the surface of the liquids surfrace.

Question 22

Fire point definition

Answer 22

Fire point is the tempurature at which sufficiant vapors are meing generated to sustain combustion reaction.

Question 23

Solubility vs Miscibility

Answer 23

Solubility is the extent a substance (solid or liquid) will mix with water until it will not mix in any more.

Miscibility is two liquids that can mix in any proportion, without ever seperating.

Question 24

Polar solvents

Answer 24

Liquids that mix readily with water

Question 25

Lower Explosive Limit, vs UEL

Answer 25

LEL is the lowest concentration at which a fuel must exist in air to support combustion. UEL is the highest concentration """ This is known as the explosive range.

Question 26

Vapor density

Answer 26

Vapor density describes the density of gases in relation to air. Air =1, Less than 1 rises such 4HMEDICANNA, greater than 1 sinks.

Question 27

4H MEDIC ANNA (wrong chapter i know, just for funsies)

Answer 27

Helium Hydrogen Hydrogen Cyanide Hydrogen Flouride Methane Ethylene Diborane Illuminating gasses Carbon monoxide Acetylene Nitrogen Neon Ammonia

Question 28

Oxidizing Agent

Answer 28

Any substance that yields O2 during a chemical reaction. The oxidizer itself is not combustible, but will support combustion.

Question 29

O2 deficiant atmospheres vs O2 Enriched effect on burn rate and temps

Answer 29

O2 deficiant, higher temps and slower burns O2 enriched, lower temps but fast rapid burns.

Question 30

Flammable range of carbon monoxide, and flashpoint temp

Answer 30

12.5% - 94%, 609°C

Question 31

Fuel controlled vs Ventilation controlled

Answer 31

Fuel limited: Fire with adequet oxygen, growth is controlled by fuel source and amount of available fuel. Ventilation Controlled: Heat release rate is dependant on amount of O2 available

Question 32

Fire stages

Answer 32

Incipiant: Fire starts and can burn freely, not yet influencing the environment. Growth: Begins to influence the environment. Fully Developed: When growth stage has reached its maximum and all combustable materials are burning. Maximum heat release, Fire is ventilation controlled. Decay: Fire consumes all availble fuel in the compartment, fire progresses into fuel limited.

Question 33

How is the growth of a fire different in the center of a room vs in a corner

Answer 33

IN the center, air is entrainef from all sides, while in a corner, air is only entrained from 2 sides resulting in a higher plume.

Question 34

Flashover definition and describe

Answer 34

Rapid transition from local burning of contents to the widespread burning of all exposed fuels in a compartment. Tempuratures can be from 450 to 650C, with up to 1200C in the smoke cloud.

Question 35

Best defences against flashover

Answer 35

Predict using signs of flashover and do not enter. Aggresivly cool from the exterior of the compartment. Use wide fog and evacuate immidiately.

Question 36

Precursors fro flashover

Answer 36

Free burning flames within the compartment Extremely high temperatures, to the point where youre being forced down to the ground. Black smoke: High volume, density, fvelocity black smoke. Rollover: smoke has flames propagating through top of smoke accross ceiling.

Question 37

Variables effecting flashover potential

Answer 37

Compartment size, Insulation qualities, Ceiling height, ventilation.

Question 38

BAckdraft

Answer 38

The explosive rapid combustion of flammible gas (smoke)., When the fire is in the decay stage producing lots of smoke, the introduction of a new source of o2 can cause a rapid transition back into a fully involved state. Potential for backdraft must be considered before makeing any opening into a compartment.

Question 39

Backdraft indicators

Answer 39

Building: fires confined to a single compartment have a high heat release rate. Smoke indicators: Dense or darkening smoke, or smoke pulsing up and down. Air flow: High velocity and turbulant Heat: high temps Flame: little to no visible flame, but heavy dense smoke.

Question 40

Smoke explosion

Answer 40

Ignition of premixed oxygen and smoke when an ignition source is introduced.

Question 41

Smoke explosion possiblity examples

Answer 41

Sparks being produced by embers, LIght switch sparks, Pilot lights