IFSTA(5th)-Chapter 3 Flashcards
physical change
substance changes size, shape, or state
Matter
anything that occupies space and has mass
chemical change
substance changes from one type of matter to another
Exothermic
heat is produced
Endothermic
heat is absorbed
Combustion
rapid, self-sustaining chemical reaction that produces heat and light
fire
form of combustion. can be smoldering or flaming
Fire triangle
fuel, oxygen, heat
best describes smoldering combustion
Fire tetrahedron
Fuel, oxygen, heat, self-sustaining chemical chain reaction. best describes flaming combustion
Heat
kinetic energy associated with the movement of the atoms and molecules in matter. measured in Joules (Newtons/meters)
Temperature
measurement of KE due to heat
KE
kinetic energy
energy of a moving object
PE
potential energy
energy within an object at rest that can be released in the future
Heat movement
from hot objects to cold ones conduction radiation convection flame impingement
Energy
capacity to perform work
Work
force applied over distance
(mass x acceleration)/distance
force
mass x acceleration
Kg)(meters/s squared
BTU
British thermal unit
amount of heat required to raise Temp of 1# of water 1 degree F.
Fahrenheit
F=(C x 1.8) + 32
Celsius
C = (F-32)/1.8
auto ignition temp.(AIT)
point at which a material ignites without an external ignition source
Pyrolysis
chemical decomposition of a substance due to heat
piloted ignition
ignition due to external source
6 energy forms that can create heat
chemical electrical light mechanical nuclear sound
oxidation
occurs when a combustible comes into contact with oxygen. when an oxygen electron is added to something. almost always produces heat.
Increase in 10 degrees C
results in most chemical reaction rates doubling
electrical heating occurs 4 ways
resistance heating
overload/overcurrent
arcing
sparking
Resistance heating
electric current flowing through a conductor
overload/overcurrent
when electric current exceeds conductor capacity
Arcing
high temp. luminous electric discharge across a gap or through a medium. e.g., when a conductor is separated, lightning, static electricity, or due to excessive voltage
Sparking
the glowing particles that spatter away from the point of arcing
Mechanical heat energy
due to friction or compression
Rate of heat transfer
is greater between 2 objects with a greater Temp. difference.
heat transfer/time.
Conduction
transfer of heat from one solid object to another solid object by direct contact.
Thermal conductivity
measure of an object’s capacity to transfer heat via conduction. the greater the conductivity, the faster the heat transfer!
insulating materials
slow conduction.
made of fine particles or fibers with lots of air filled voids.
because molecules are far apart in gases, air doesn’t conduct heat very well.
Convection
transfer of heat from a liquid or a gas to a solid
Radiation
transmission of heat energy as an electromagnetic wave through space.
examples: infrared, radio, x-rays
360 degree spread at the speed of light
As Temp. increases the radiant energy…
increases by a factor to the 4th power. for example: if T is doubled, then 2 to the 4th is 16. so T is doubled and the radiant energy is 16x greater
Passive agents
substance such as water that is inside a substance or within a gas and absorbs heat but does not participate actively in combustion. relative humidity and fuel moisture are examples.
Reducing agent
the fuel that is being oxidized. it is being reduced 2 ways: reduction of fuel and the addition of electrons(negative charge)
organic
contains carbon
2 types of organic fuels
hydrocarbons
cellulose-based materials
flaming combustion only occurs in which state?
gaseous
Vapor density
if > 1 the gas will sink
if < 1 the gas will rise
methane VD
0.55, rises
Propane VD
1.52, sinks
LPG
liquid petroleum gas
also known as propane
CO VD
carbon monoxide
VD=0.96, rises
Specific Gravity
if SG < 1, floats on water
if SG > 1, sinks in water
Vaporization
transformation of a liquid to a gas
Rate of Vaporization depends on…
vapor pressure of substance
amount of heat energy applied
Flash Point
Minimum Temp. when a liquid gives off enough vapors to form an ignitable mixture with air.
Fire Point
Temp. at which a liquid fuel produces enough vapors to support combustion once the fuel is ignited. normally a few degrees higher than the flash point.
As surface area of a liquid increases, vapor production…
increases
solubility
degree of a substance to dissolve in a solvent (usually water)
Polar sovents ____ with water
mix
Hydrocarbons_____with water
do not mix
SG gasoline
0.72, floats on water
Miscible
material that can mix with water in any proportion
SG diesel
is > 1, sinks
SG ethanol
= 0.78, floats
SG methanol
= 0.79, floats
for solids, as surface-to-mass ratios increase, ignitability…
increases
4 stages(Temp. Ranges) of Pyrolysis
< 392 degrees F, moisture is being releases
392 - 536 degrees F, charring begins
536 - 932 degrees F, rapid pyrolysis occurs, charcoal is produced, ignition can occur
> 932 degrees F, free burning as wood is converted to flammable gases
Do solids burn more rapidly due to position?
yes, due to convection solids that are vertical burn more rapidly
Heat of Combustion
total amount of energy released when a fuel is burned(oxidized).
kiloJ/gram
HRR
heat release rate
energy released over time for a given fuel
“Oxygen deficient”
atmosphere with less than 19.5% oxygen
“oxygen enriched”
atmosphere with > 23.5% O2
Common Oxidizers(other than O2)
calcium hypochlorite-chlorination of water in pools
chlorine gas-water purification
ammonium nitrate-fertilizer
hydrogen peroxide-antiseptic, industrial bleaching
methyl ethyl ketone peroxide-plastics
31% O2
O2 concentration that Nomex ignites and readily burns
Flammable(explosive) Range
range of concentrations of fuel vapor and air that allow for combustion. LFL-UFL lower flammable limit to the upper flammable limit
“Lean”
fuel vapor concentration in air is < LFL
“rich”
fuel vapor concentration in air is > UFL
Common Flammable Ranges
methane: 5-15%
propane: 2.1-9.5%
CO: 12-75%
gasoline: 1.4-7.4%
diesel: 1.3-6%
ethanol: 3.3-19%
methanol: 6-35.5%
Methane is also known as _____
natural gas
free radicals
electrically charged, highly reactive parts of molecules that combine with other components of a fuel to create new substances
Chemical flame inhibition
extinguishing agent interrupts the self-sustaining chemical reaction and terminates combustion. halon is an example…or a halon replacement. this cannot be done on smoldering combustion
Smoke
mixture of gases, vapor, and solid particulates
CO
carbon monoxide
asphyxiant
formed by the incomplete combustion of carbon
combines to hemoglobin 200x quicker than O2
CO2
carbon dioxide
colorless, odorless, heavier than air.
neither burns or supports combustion.
used as an extinguishing agent by displacing O2 or smothering fires
HCN
hydrogen cyanide
produced in the combustion of materials containing nitrogen. produced when polyurethane foams burn (furniture/bedding)
prevents the body from using O2 at the cellular level.
flame
visible, luminous body of a burning gas
Class A Fire
ordinary combustibles
wood, cloth, paper, plastics, rubber, grass, etc.
primary extinguishment via cooling with water
Class B Fires
flammable liquids and gases
remove supply
use class B foams to blanket or dry chemicals.
Class C Fires
energized electrical fire
de-energize before extinguishment.
Class D Fire
combustible metals aluminum magnesium potassium zirconium titanium sodium
Class K Fire
cooking fuels
Saponification
when extinguishing agents turn fats and oils into a soapy foam that extinguish the fire
fuel controlled fire
when O2 is sufficiently available
Ventilation controlled fire
when fire is limited by air supply
4 stages of fire
incipient
growth
fully developed
decay
Incipient stage
ignition occurs
fuel controlled
mostly confined to the material burning
Growth Stage
2-in/2-out is now required
rapidly increasing heat
other materials are now burning
Thermal layering
gases form into layers according to temperature. hottest are at the ceiling and coolest are at the floor.
also known as stratification and thermal balance.
Neutral plane
where high pressure gases level off thru an opening with inward moving cooler air.
Rollover
when fire gases ignite at the ceiling level and flames propagate through the hot gas layer across the ceiling
Flashover
rapid transition from growth to fully developed fire stage that is when all contents within a structure reach their ignition Temp. and flames erupt all at once.
Flashover Indicators
lower hot gas layers strong bidirectional air/smoke movement rapid increase in heat isolated flames in a hot gas layer rollover
flashover Temp. Range
900-1200 degrees F
btw, CO auto ignites at 1128 F
Fully Developed Fire
when all combustible materials in a compartment are burning
Decay
when most fuel has been consumed or the O2 has diminished enough where flaming combustion is no longer supported
Is decay fuel or ventilation controlled?
fuel
Fully developed fire is _____ controlled
ventilation
Backdraft
instantaneous explosion or rapid burning of superheated gases that occurs when O2 is introduced into a confined space
Deflagration
explosively rapid combustion
T or F. the more confined the deflagration, the more violent it will be.
true
Backdraft Indicators
little or no visible flame inward sucking smoke pressurized smoke exiting small openings smoke puffing dense gray/yellow smoke smoke stained/cracked windows confined excessive heat
6 factors that affect fire development
fuel type location/availability of another fuel compartment shape ventilation thermal properties of structure ambient conditions(wind/temp/humidity/etc)
HVAC
heating ventilation and AC
4 thermal properties that affect fire
insulation
conductivity
retention
reflection
4 ways to control fire
temp. reduction
O2 exclusion
fuel removal
inhibit chemical reaction
