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