BOOK 83 - FIRE INVESTIGATION MANUAL Flashcards
The responsibility for the investigation of fires is shared between the
Bureau of Emergency Services and the Bureau of Fire Prevention.
which has the primary responsibility for the cause determination of fires
Bureau of Emergency Services
Who is responsible for the protection of the public from those people who set fires.
The fire department
Who has the primary responsibility to determine the cause of all fires, criminal and non-criminal.
The Bureau of Fire Suppression and Rescue
The Bureau of Emergency Services also has the follow-up investigation responsibility of fires where the total loss is less than
$25,000.
As per the Manual of Operation, the responsibility for determining the most probable cause of a fire rests with the
Incident Commander.
refers to the fire scene investigation and subsequent investigation needed to establish the cause.
preliminary investigation
refers to the criminal investigation necessary to seek the prosecution of an arsonist.
follow-up investigation
The Arson Investigation Section is organized to provide limited fire investigation service for the City of Los Angeles on a __hour basis.
24 hour
The amount of heat required to raise the temperature of one pound of water one degree Fahrenheit (measured at 60 degrees F.).
British Thermal Unit (B.T.U.)
Liquids having a flash point at or above 100 degrees F.
Combustible liquids
Rapid oxidation of a substance accompanied by the release of energy usually in the form of heat and light.
Fire
The lowest temperature of a liquid in an open container at which vapors evolve fast enough to support continuous combustion.
Fire point
describes the minimum concentration of vapor-to-air below which propagation will not occur in the presence of an ignition source.
lower flammable limits
the maximum vapor-to-air concentration above which propagation of flame will not occur.
upper flammable limit
Liquids having a flash point below 100 degrees F.
Flammable liquids
The minimum temperature at which a liquid gives off vapors in sufficient concentrations to form an ignitable mixture with air near the surface of the liquid.
Flash Point
A form, of energy associated with the motion of atoms and molecules.
Heat
The amount of heat released during the complete oxidation of a substance.
Heat of combustion
The minimum temperature to which a substance must be heated in air in order to initiate or cause combustion, independent of the heating element or source.
Ignition temperature
The ignition temperature of ordinary combustibles is between
300 and 1000 degrees F.
As a substance burns, it mixes with oxygen and produces heat.
Oxidation
The ratio of the weight of a solid or liquid substance to the weight of an equal volume of water.
Specific gravity
The quantity of heat concentration. The intensity of heat is measured in degrees (Fahrenheit or Celsius).
Temperature
The weight per unit volume of a pure gas or vapor.
Vapor density
A vapor density less than __ indicates a vapor lighter than air.
1.0
Class “_” fires are fires involving ordinary combustible fuels.
Class A
Class “_” fires are fires involving liquid fuels.
Class B
Class “_” fires are fires involving energized electrical equipment.
Class C
Class “_” fires are fires involving combustible metals.
Class D
The fire triangle
Heat
Fuel
Oxygen
The fire tetrahedron
In reality, fire has four parts which are necessary for self-sustaining, open flaming combustion:
Heat
Fuel
Oxygen
Uninhibited chain reaction among all parts of the tetrahedron.
When certain extinguishing agents are introduced, it breaks up this chemical reaction and extinguishes the fire without affecting the heat, fuel, or oxygen sides of the fire triangle. These extinguishing agents are:
Dry chemical
Halon
the chemical decomposition of matter through the action of heat.
Pyrolysis
Early indications of the pyrolysis process are usually observed as discoloration of the
Fuel
As pyrolysis continues, combustible gases are released and a black carbon residue called “___” remains.
Char
If the fuel continues to be heated slowly, but there is not sufficient heat present to reach ignition temperature, ____ ____ may result.
Pyrophoric carbon
What is usually the key element in ignition (and extinguishment) of most fires.
Heat
Heat is transferred in four ways:
Conduction
Convection
Radiation
Direct flame impingement
The transfer of heat from one object to another through direct physical contact.
Conduction
The transfer of heat by some circulating medium (liquid or gas). This is the form of heat transfer most responsible for fire spread in structural fires.
Convection
The transfer of heat as energy traveling through space or materials as waves.
Radiation
Direct flame contact with combustibles.
Direct flame impingement
Phases of fire:
Incipient phase
Free burning phase
Smoldering phase
Oxygen in the area remains near 21%. Thermal updraft causes heat to accumulate at the higher portions of the area. What stage is this
Incipient stage (growth)
“Mushrooming” may take place and flame is present. oxygen content of area is usually reduced to 16% - 18%. “Flashover” frequently occurs during this phase.
Free burning (fully developed)
Area fills with dense
smoke. Oxygen may drop below 15%. Temperatures may reach 1000 degrees
Smoldering phase (Decay)
an explosion or rapid burning of heated fire gases resulting from the introduction of oxygen when air is admitted into a building heavily charged by smoke from a fire which has depleted the oxygen content of a building.
Backdraft
Carbon monoxide is one of the most common gases found in structural fires and is highly flammable. (Explosive limits =
12.5%-74%
The ignition temperature of carbon monoxide
1128 degrees F
is the stage of the fire when all combustibles in an area have become heated to their ignition temperature, then ignite simultaneously.
Flashover
Buildings of steel, iron, concrete, or masonry.
Type I - Fire Resistive
Noncombustible/fire-resistive, one-hour, or no-hour construction.
Construction in which walls, partitions, and structural members are of noncombustible material but do not qualify as Type I Fire-resistive.
Type II
Construction in which exterior bearing walls or bearing partitions of exterior walls are of noncombustible materials and have a minimum hourly fire-resistive rating. Wood allowed for interior use.
Type III - Ordinary construction
Construction where exterior bearing and non-bearing walls are noncombustible and have a minimum fire-resistive rating of four hours. Columns, beams and girders are commonly heavy timber with wood floors and roof construction built without concealed spaces. “
TYPE IV
Construction in which exterior walls, bearing walls, partitions, floors and roofs as well as their supports are wholly or partly wood or other combustibles.
Type V - Wood frame construction
The weight of the building and any equipment permanently
attached or built-in.
Dead loads
Any load other than a dead load. vary with intended or actual use of the structure.
Live loads
Loads which are delivered in a short period of time. Examples are explosions, wind (lateral analysis), and earthquakes.
Impact loads
The total number of British Thermal Units (BTU) which might be
evolved during a fire in the building or area under consideration and the rate at which the heat will be evolved.
Fire loads
Attic areas (Unprotected concealed space) cannot exceed ____
square feet without fire walls
3000 SQFT
The process of determining cause and origin of a fire starts prior to arrival on the fire scene. Some considerations are as follows:
Type of occupancy
Time of day and day of week
Color of fire and smoke
As the amount of hydrocarbons increase, the flames will become _____ and more _____ in color.
Darker and more orange
Then examine the interior of the structure, working from. the ____ to the _____ damaged fire areas.
Least to the most
____ ____ Then examine the interior of the structure, working from. the LEAST to the MOST damaged fire areas.
Burn patterns
_______ and ______ play a major role in producing burn patterns.
Convection and radiation
Factors that may influence the burn patterns:
Fuel load
Venting
Firefighting activities
Weather
The normal growth of a fire is usually upward and outward. This burning usually produces a
V pattern
diffused line of demarcation usually indicates a slow smoldering combustion.
Wide “V” pattern
sharp line of demarcation may indicate flaming, rapid combustion.
Narrow “V” pattern
sharp line of demarcation may indicate flaming, very rapid combustion; possible presence of flammable accelerants.
Inverted “V” pattern
In some cases, “V” may be
vertical, horizontal or a combination of both.
“V” patterns may extend around
corners, walls and doors
_____ structural elements may form “V” patterns.
Interior
Douglas fir burns at the rate of approximately one inch in ____-____ minutes
40-45
Hardwoods burn at the rate of about __ inch in 40-45minutes and pine burns at a faster rate than fir.
3/4
is usually found near the point of origin and may be a good indicator to help locate the point of origin.
Deep char
factors that may effect charring are:
______
____ of the product
______ content
______/_____ of the product
_______ of the fire
Existing _____ _____ around the product
Firefighting ______ & ________
Ventilation
Age
Moisture
Hardness/density
Temperature
Tactics and strategies
the explosive breaking off of pieces of masonry materials such as concrete or brick during exposure to fire.
Spalling
Spall only suggests a possibility of the presence of
lammable liquid
Spalling can be caused by rapid contraction of the surface of the concrete as a result of application of
Hose streams
caused by the application of a flammable liquid to a surface covered with asphalt tile.
Ghost marks
Light bulbs
When subjected to___ degrees F., may swell toward the point of heat.
900
the ballast transformers are designed to operate continuously at approximately __degrees F, but the temperature often goes higher
90
Ballast transformers have a life expectancy of
15 years.
Factors that effect glass behavior
Age
Thickness
Type
Temperature variation (inside to outside)
Country of manufacture
Smoke stains Stops forming when temperatures reach ___degrees F.
700
_____ of glass usually caused by rapid buildup of heat during the fire.
Crazing
____ _____ of glass
Usually larger than crazed glass.
Usually caused by slower heat buildup.
Heat fracturing
half-moon shape found on surface of glass.
Usually results from water being applied to heated glass.
Checkering of glass
Calcination of drywall/sheetrock
Naturally contains __% water which is chemically bound in the
product.
21%
Dehydration of gypsum is called
“calcination”
Heat exposure causes it to undergo calcination (____+ degrees F.).
105
The average automobile contains over ___ pounds (approximately 13%) of plastics which are derived from petroleum products.
300
A properly operating catalytic converter can reach internal temperatures of
1600 degrees
An improperly operating converter may generate an external temperature of approximately
2500 degrees
Wildland Fire travel is controlled by
Weather, wind, fuel, and topography
Cigarettes may not ignite dry vegetation unless the relative humidity is under
22%
defined as the sudden and rapid escape of gases from a confined space, accompanied by high temperatures, violent shock, and a loud noise.
Explosion
___ pressure waves result from an explosion.
Two
Positive and negative
. The negative wave has about __ percent of the power developed by the positive wave.
60%
any explosion that occurs within a container or vessel.
A mechanical explosion
Mechanical:
This condition might only occur for a _________ as in the case of a pipebomb.
Millisecond
caused by the rapid conversion of a chemical compound into gases.
A chemical explosion
occurs within the atom of an element and may be either nuclear fission or nuclear fusion.
A nuclear explosion
can occur in any industrial occupancy where combustible dusts are created and allowed to accumulate.
Dust explosions
High explosives have a shock wave of approximately _____ feet per second.
25,000
A critical fact to keep in mind is that all fires should be considered ______ at the beginning of each investigation.
Accidental
Spontaneous heating as a straight chemical reaction , a process of oxidation or a fermentation known as
Thermogenesis
Heat buildup in insulation adjacent to wiring.
Overcurrent
Heat buildup caused by an arc, where a spark travels across a gap.
Arcing/Sparking
The discharge of electrical energy from a cloud to an opposite charge on another cloud or the ground.
Lightning
The mechanical energy used in overcoming the resistance to motion when two solids are rubbed together.
Frictional Heat
Resulting from the impact of two hard surfaces, one of which is usually metal.
Friction Sparks
Friction Sparks
Depending on the metal, the temperature of these sparks can range from ___ to over ____degrees Fahrenheit,
500 to 2500
The ignition of a fire is dependent upon:
Mass (amount) of the fuel
State of the fuel
An event which brings the heat source and the fuel together can be:
an Action (Acts)
a Lack of Action (omissions)
The very small negatively charged particles which are practically weightless and circle (orbit) the nucleus of an atom.
ELECTRON
Electrons that have left their orbit in an atom and are wandering free through a material.
FREE ELECTRONS
The movement of free electrons.
ELECTRIC CURRENT
A deficiency of electrons.
POSITIVE CHARGE
A surplus of electrons.
NEGATIVE CHARGE
Materials that permit the free movement of many electrons such as silver, copper.- aluminum, zinc, brass, and iron (listed in order of ability to conduct).
CONDUCTORS
Materials that do not permit the free movement of many electrons such as dry air, glass, ceramics, mica, rubber, and plastics (listed in order of their ability to insulate).
INSULATORS
The ability of a source of electrons to overcome resistance. As compared to a water system, it would be water pressure.
POTENTIAL (VOLTS)
Rate at which electrons pass through a circuit. As compared to a water system, it would be gallons per minute.
CURRENT (AMPERES)
Opposition offered by a material to the flow of current. As compared to a water system, it would be friction loss.
RESISTANCE (OHMS)
Rate of energy use or dissipation. The product of POTENTIAL x CURRENT
POWER (WATTS)
Current that always maintains a direction of electron flow.
DIRECT CURRENT
Current will periodically change the direction of electron flow (regulated at 60 times per second in the United States)
ALTERNATING CURRENT
A partial or total failure in the insulation or continuity of a conductor.
FAULT
An insulation failure between a conductor and ground, where the failure is not to a grounded conductor normally intended to carry current in the circuit.
GROUND FAULT
A fault where there is an abnormal connection between two points of different voltage in a circuit.
SHORT CIRCUIT
electricity at rest
Static Electricity
AN ELECTRIC CIRCUIT HAVING VOLTAGE SUPPLIED TO IT BUT NO CURRENT FLOW WILL NOT CAUSE
Ignition
Almost every residential building in the United States has a potential of ___ volts service.
230 volts
The electrical power enters the structure through ____ wires.
Three wires
Residential electrical systems
The voltage of the other two conductors has a potential from the grounded conductor of
115 volts
The incoming power flows through the service entrance conductors to the_____ ______ meter which monitors and records the amount of electricity used.
watt- hour meter
Conductors are, generally made of
Copper or aluminum
All building wire will have the code printed on the ______ or _______ of the wire or cable.
Covering or jacket
Common building wire is rated for continuous service at ____ degrees F. maximum.
140 degrees
T” Thermoplastic ___
degrees
“R” Rubber ___ degrees
“H” Higher Temperature ___ degrees
“HH” Higher Temperature ___ degrees
140
140
167
194
Insulation Color
Grounding wire
Bare or green
Insulation color
Grounded
White neutral
Insulation color
Hot
Black line or other colors
The conductor must be of such size so voltage drop is not excessive. Generally, size must be adequate to supply the load without exceeding a __% drop in voltage.
2%
The melting temperature of copper is listed as ___ degrees F.
1981
In recent years smoking related fire deaths have accounted for nearly a ____ of all residential fire deaths where the cause of fire was known.
Third
Legislation was passed requiring that any mattress sold in the United States be-cigarette resistant. What year
1973
Requirement that every piece of furniture sold in California be flame retardant and smolder resistant. In 1980, this requirement was made more restrictive.
What year?
1975
Most upholstered furniture (chairs, sofas, etc.) and mattresses are made with cover fabrics and porous stuffing materials whose ignition temperatures
500-700
Smoker type fires typically take from __ minutes to ___ hours to develop into the free burning phase.
20 mins to 2 hours
