fire dynamics
fire in fuel packages can only entrain air from
2 sides
fire in fuel packages near walls entrain air from
3 sides
the quantity of heat required to change the temperature of 1 gram of water by 1 degree celsius is
4.2 joules
Combustion
A chemical process of oxidation that occurs at a rate fast enough to produce heat and usually light in the form of either a glow or flame.
chemical flame inhibition
Extinguishment of a fire by interruption of the chemical chain reaction.
asphyxiation
Fatal condition caused by severe oxygen deficiency and an excess of carbon monoxide and/or other gases in the blood.
autoignition
Initiation of combustion by heat but without a spark or flame.
backdraft
Instantaneous explosion or rapid burning of superheated gases that occurs when oxygen is introduced into an oxygen-depleted confined space. The stalled combustion resumes with explosive force; may occur because of inadequate or improper ventilation procedures.
Autoignition Temperature (AIT)
The lowest temperature at which a combustible material ignites in air without a spark or flame.
concentrations above the ---- are said to be too rich to burn
UEL
any open space with no complete fire barriers dividing it is considered
a compartment
all fires involve
a heat producing chemical reaction
all fuel is
a reducing agent
in the case of heat, work means increasing - ------ --------
a substance's temperature
what is a feature of older structures built prior to approximately 1990?
air pockets in empty wall cavities
fire in fuel packages in the middle of the room entrains air from
all sides
the energy release in fire is directly proportional to the
amount of oxygen available for combustion
Combustion zone
area surrounding a heat source in which there is sufficient air available to feed a fire
the best indicators of the structural integrity of a burning building are gathered
at the scene
in which kind of structure is bowstring truss most likely to be found
bowling alley
gaseous combustion products rise and move away from the fire due to
buoyancy
production of complete combustion of organic materials; creates an oxygen deficient atmosphere
carbon dioxide
toxic and flammable product of the incomplete combustion of organic materials
carbon monoxide
in terms of fire behavior, which potential energy of a fuel converts into heat and light during combustion
chemical
the rate at which fuel releases energy over time depends on
chemical composition arrangement density of the fuel availability of oxygen for combustion
what occurs when an extinguishing agent interferes with this chemical reaction, forms a stable product, and terminates the combustion reaction
chemical flame inhibition
carbon monoxide
colorless, odorless, dangerous gas. toxic and flammable. formed by incomplete combustion of carbon. binds with hemoglobin 200 times faster than oxygen and decreases blood ability to carry oxygen
carbon dioxide
colorless, odorless, heavier than air gas that neither supports combustion nor burns. used in portable fire extinguishers, puts out class b or c fires
the transfer of heat through and between solids
conduction
wood shakes, when treated with fire retardant, can significantly ________ to fire spread
contribute
transfer of thermal energy by circulation or movement of a fluid
convection
consumes the available fuel or oxygen and the heat release rate begins to decline
decay stage
reactions that absorb energy as they occur are
endothermic reactions
kinetic energy is
energy that moving object has
potential energy
energy that will release at some point
reactions that emit energy as they occur are known as
exothermic
temperature is an accurate measurement of heat transfer
false
two modes of combustion
flaming and nonflaming
When sufficient oxygen is available for flaming combustion, the fire is said to be ------ ------
fuel limited
carbon based fuels
fuels where the energy of combustion derives from carbon ex: wood, cotton, coal, or petroleum
when all combustible materials in the compartment are burning at their peak heat release rate based on the available oxygen
fully developed stage
more of the initial fuel package becomes involved and the production of heat and smoke increases
growth stage
flaming combustion requires liquid or solid fuels to be converted to the gas phase through the addition of
heat
potential energy available for release in the combustion process is
heat of combustion
gases move from areas of _____ pressure to areas of ______ pressure
higher, lower
ceiling jet
horizontal movement of a layer of hot gases and combustion byprods from the center point of the plume when a horizontal surface redirects vertical development of the rising plume
significant byproduct of the combustion of polyurethane foam used in many household furnishings
hydrogen cyanide
starts with ignition when the three elements of the fire triangle come together and the combustion process begins
incipient stage
smoke is the product of
incomplete combustion
the thermal properties of the building that can contribute to rapid fire development are ------, ----- ----, and -----
insulation, heat reflectivity, retention
when a fire cannot grow without the introduction of fuel source or a new oxygen source
it has left the growth stage and become fully developed
hypoxia
lack of oxygen
what type of combustion occurs more slowly and at a lower temperature, producing a smoldering glow in the material's surface
nonflaming
the ------ of the fuels as well as their ---- --- -- ----- will also influence the rate and intensity of fire spread
orientation, surface-to-mass-ratio
the oldest and simplest model, the fire triangle, shows three elements necessary for combustion to occur: ----, ----, and ----
oxygen, fuel, heat
energy is the capacity to
perform work
most common form of ignition
piloted
the amount of energy delivered over a given period of time is the definition of
power
what is an indicator for backdraft
pulsing smoke
common cause of exposure fires
radiation
transmission of energy as electromagnetic waves, such as light waves, radio waves, or x rays, without an intervening medium
radiation
which of the following is a significant indicator of flashover
rollover
example of oxidation
rust
Gases with a vapor density greater than 1 will:
sink
which of the following can occur when a mixture of unburned fuel gases and oxygen comes in contact with an ignition source
smoke explosion
ignition without the addition of external heat in known as
spontaneous
buoyant
tendency or capacity of a liquid or gas to remain afloat or rise
the tendency of gases to form into layers according to temperature, gas density, and pressure
thermal layering
four flashover indicators
transition from growth to fully developed rapidity enclosed space fire gases ignite
liquids that are less dense than water are difficult to extinguish using water as the sole extinguishing agent
true
oxidizers are combustible
true
oxidizers are not combustible but will support or enhance combustion
true
piloted ignition occurs without any external flame or spark to ignite the fuel gases or vapors
true
when firefighters ventilate windows or make entry into a building, they establish new flow paths between the fire compartment and exterior vents of the building
true
while the heat from a fire is a danger to anyone directly exposed to it, exposure to toxic gases found in smoke and/or lack of oxygen causes most fire deaths
true
------- ------ occurs when when a structural member fails and introduces a new source of oxygen to the fire
unplanned ventilation
most residential fires that develop beyond the incipient stage become ---------------
ventilation limited
there are two main types of fully developed fires: fuel-limited and ----- -----
ventilation limited
heat transfers from ______ objects to _______ objects.
warmer, cooler
heat is a form of
work