highlighted sections Flashcards
how often should the scientific method be applied when conducting fire investigations?
every time
Although 921 is entitled a guide, it is considered to be what?
the standard of care for fire investigations
What is the purpose of NFPA 921?
to establish guidelines and recommendations
What are the steps of the sciencific method?
recognize a need define the problem collect data analyze the data develop a hypothesis test the hypothesis select the final hypothesis
Is it ok to use speculations when analyzing data>
no, only facts and direct observations should be used
What is the purpose of the hypothesis
it is to provide an orientation for further data collection efforts
two things to do when testing a fire origin and cause hypothesis
- eliminate all other reasonable origins and fire causes
2. compare the hypothesis against known fire dynamics
The standard for Professional Qualifications for Fire investigator is
1033
a search under the 4th amendment occurs when…
a governmental employee or agent of the government violates an individual’s reasonable expectation of privacy
two requirements to plan view
- right to be there
2. evidence is in plain view
Post flashover damage is similar to full-room involvement damage without flashover which includes what?
- relatively even floor burning
- relatively even charring on surfaces
- surface burning on contests and furnishings
is establishing the burn-time by depth of char reliable?
no
3 types of drafts caused by fire department activities
- premature venting of structure
- improper ventilation location
- forced ventilation before extinguishment
Normal fire growth is what and produces what?
normal growth is upward and outward and produces a V-shaped fire pattern on vertical surfaces.
What is the total quantity of combustible contents including interior finishes and trim?
fire load
does total fuel load have any effect on the rate of fire growth in the pre-flashover stage?
no
fire growth before flashover is determined by what?
the heat release rate of the burning fuel
following flashover, the heat release rate is determined by what?
- the heat release rate of the burning fuel,
- the amount of air
- the exposed combustible contents
fire scenes should be ____ when possible
reconstructed
reconstruction of fire scenes helps what?
id the point of origin
id fire causes
what are protected areas?
unburned areas that were protected from something on top of them that reduces the oxygen below it or covered the combustible fuels
T or F: Arc mapping must be used in combination with other techniques, such as burn patterns and reconstruction
True
What is “the circumstances, conditions, or agencies that bring together a fuel, ignition source, and oxidizer resulting in a fire or a combustion explosion?”
fire cause
define fire cause
the circumstances, conditions, or agencies that bring together a fuel, ignition source, and oxidizer resulting in a fire or a combustion explosion
5 types of electrical heat energy
- resistance heating
- induction heating
- dielectric heating
- heat from arcing (including static)
- heat generated by lightning
what type of electrical heat energy is created when electric current flows through a conductive material?
resistance
What type of electrical heat energy is created when heat of material where an electric current is caused to flow through the material or its container?
induction heating
what is high-frequency heating, microwave?
dielectric heating
3 types of fire causes per nfpa 921
accidental
incendiary
undetermined
Before a fire can be determined to have been incendiary, what must be eliminated?
all accidental causes must be
one of the most common causes involving heating equipment is…
combustibles being places too near the heating unit
what are the indicators of a smoldering fire in furniture?
the collapse of springs (over 750 degrees is required to produce a loss of spring tensile strength.
DC or AC - electric current flowing continuously in one direction through a circuit at a constant rate
DC
DC or AC - constantly changing intensity and direction
AC
Volt, Amp, or Watt? the pressure (electromotive force) of the electricity in a circuit
volt
Volt, Amp, or Watt?
the quantity of electrictiy flowing through the circuit
amp
Volt, Amp, or Watt?
the unit of power (rate of doing work)
watt
Amps = ______ divided by ______
wattage, voltage
Watt = _______ multiplied by ______
voltage, amperes
What is the friction encountered by the electric current?
resistance
what is electrical resistance?
friction encountered by the electric current
electrical resistance is determined by what? (3 things)
size of the wire
the material of which it is made
length of the wire
electrical resistance produces what?
heat and drop in voltage
What type of buildings receive electricity through three wires (single-phase service)
Most residential and smaller commercial
Single phase consists of what wires
two insulated 120-volts and an uninsulated neutral wire
What is it when a hot wire in contact with some other object capable of supporting current flow?
ground flow
What is it when a hot wire is in contact with neutral wire?
direct short circuit
most residential breakers are what type?
thermal-magnetic type
______wire have less resistance than _____ wires and carry more current
larger, smaller
Pure copper melts at _____ degrees F.
1980
Pure aluminum melts at _____ degrees F.
1220
what causes aluminum connections to loosen and heat
thermal expansion
What is a resistance heating
it is heat that is generated when a conductor is overloaded
what is a common cause of resistance heating
cords carrying too great a load
electrical arcs can generate temperatures over _____ F
34,000
when overheating occurs in a screw-type fuse, isinglass usually shows what?
little or no burning or discoloration
when a short circuit occurs in a screw-type fuse, isinglass usually shows what?
discolor (dark spot on the glass)
what is a visual indicator that a mechanical break from objects strikes a wire?
flat ends
What is a major cause of electrical fires?
loose or failed connections
a common problem with recessed lighting is
that it may have a light bulb of excessive wattage installed
when looking at recessed lighting, always check for what?
insulation packed on top of the fixture which prevents heat and dissipating and can ignite surrounding materials.
What is a common reason for electrical blankets to cause a fire?
misuse by owner
What are the most common causes of fas-fueled fires
leaks from pipes or equipment
3 ways that spontaneous heating can be produced
chemical action
oxidation
fermentation or microbial thermogenesis
before a fire can be ruled incendiary, what must be eliminated
every reasonable accidental cause
do all or only close to the area of origin do major accidental ignition sources throughout a structure need to be examined?
all
what type of item used to causes incendiary fires are one of the most difficult to prove and easiest to set
available combustibles
if multiple points of origin, do you need to eliminate all accidental fires at each location?
yes
What is a trailer?
any combustible or flammable material used to spread the fire from one area to another
3 things to about using waxed paper as a trailer
- burns slowly and without extreme heat
- may not burn surface it burned on
- leaves fire ash which may be difficult to find
flammable liquids have flash points above or below 100F
below
combustible liquids have flash point above or below 100F
above
according to 921, what is a doughnut-shaped pattern
the irregularly shaped burn area surrounds a less burned area, may result from an ignitible liquid
how do doughnut-shaped patterns occur?
it happens when the vapors burn as the liquid protects and cools the floor surface
floor tile or vinyl floor blistering occurs from what and occurs how often?
occurs from heating the floor covering and can occur in any fire
_____ is a result of concrete being heated
spalling
spalling may be caused by (3)
heated concrete cooled by water
moisture within the concrete
age or mixture of concrete
spalling is common in ______
total fire loss
incendiary devices are classified by the type of ignition mechanism, what are the 3?
chemical
electrical
mechanical
thermite may reach temperatures of up to _____F
4300
what can burn through steel?
thermite
Molotov cocktails may fail for four common reasons
- thick glass bottle used
- bottle does not strike a solid object
- self-extinguishes in flight
- wick falls out during flight
homemade napalm is a mixture of what?
gasoline and styrofoam
T or F. A valid fire cause cannot be determined unless the area of origin has been identified and confirmed
True
What is the destruction of, failure to save evidence, or alteration of evidence that could have been used by another in future litigation?
spoliation of evidence
what is spoliation?
destruction of, failure to save evidence, or alteration of evidence that could have been used by another in future litigation?
What is a graphic portrayal of the scene or incident and of items within the scene that are of interest to the investigation
a sketch
What is the primary purpose of a sketch?
orientation
What is the most important thing to write on sketches?
“not to scale”
What is the most common plotting method for fire investigation?
rectangular coordinates
What must be kept if an image is enhanced?
an original image and you must state the extent to which the image was enhanced
What is the biggest problem when photographing fire scenes?
poor lighting
the primary purpose of field notes?
help to recall incidents, situations, and details
What is a pugilistic attitude?
post mortem, the boxer-like stance of flexed elbows and needs, clenched fist, caused by the shrinkage of body tissues and muscle due to dehydration caused by heating
studies have shown that up to ___% of fire victims die from CO poisoning
60%
CO binds with hemoglobin ____ times more than oxygen
210
HCN is _______
hydrogen cyanide
HCN is ____ times more toxic than CO
35
_____ is the “deliberateness” of an act
intent
What is the most deadly type of fire motive?
spite and revenge
serial arson is committed by firesetters who _____
set 3 or more fires with a significant cooling-off period between fires
the average age for juvenile firesetters between ___ and ___
4, 9
are all juvenile-set fires arson?
no
what is a sudden conversion of potential energy (chemical or mechanical) into kinetic energy with the production and release of gas(es) under pressure
explosion
what are low-order explosions
incomplete detonation or complete detonation at or below 3300 feet per second (pushing apart explosion)
what are high order explosions?
complete detonation above 3300 fps
what makes an explosion a seated explosion
those that create a crater or damage at the center of the blast area
what is the blast pressure effect?
as gases are produced and expand outward from the point of origin, they produce a pressure front that is primarily responsible for the damage
explosions will take the avenue _______ in a structure
of least resistance
what should you do before evidence is collected?
photographed in place
where would an investigator use a grid search during explosion investigation?
used closer to the blast site
what is the difference between an admission and a confession?
admission is a verbal acknowledgment of guilt and confession is a signed statement acknowledging guilt
Which interviews must be thoroughly documented?
all
the value of any information obtained is largely dependent on _____ and ______
validity, reliability
what is a theory or tentative explanation?
hypothesis
what can an expert witness provide that a fact witness can not
opinions
4 elements on whether an expert witness testimony can be admitted
- is the evidence beyond the normal understanding of the jury?
- is the evidence relevant
- is the witness qualified to give an expert opinion
- are the expert’s opinions and methods reliable
in a civil case, the preponderance of the evidence =____% or more
51
