SABT 5 D FIRE SCENE INV Flashcards
-Three basic elements of fire = Heat, Fuel, Oxygen
FIRE TRIANGLE
1 -
A rapid oxidation process, which is a chemical reaction resulting in the evolution of light and heat in varying intensities.
FIRE
- Expanded upon the fire triangle to include the uninhibited (Chemical) chain reaction to a four side solid geometric form called a ______
- continue as long as all three are there Heat, oxygen, fuel
FIRE tetrahedron
2 Explain fire growth as it relates to the
- three methods of heat transfer and the
- three types of fuel.
- 1 Conduction-heat transfer to another body or within a body by direct contact (needs a body to get thru)
- 2 Convection- Heat transfer by circulation within a medium, such as a gas or liquid (side of flame is Radiation/ top is heat) Go thru air heat rays
- 3 Radiation- Heat transfer by way of electromagnetic waves.
-1 Solid
-2 Liquid
-3 Gaseous
Convection and Radiation are the primary source of the fire
Types of Combustion
Spontaneous
Smoldering
Premixed
Diffusion
Extremely slow oxidation of a fuel due o the limited exposure to air
- Temperature rise in the fuel in inversely proportional to its ability to dissipate heat
- Insufficient heat loss may lead to a thermal runaway
- Process from inception to ignition may range from hours to days
Spontaneous Combustion
Combustion with flame, usually with incandescence and smoke
Smoldering combustion
Any flame in which the fuel and oxidizer are initially mixed and ignited
Pre-Mixed Flame
A flame in which fuel and air mix or diffuse together at the region of combustion
Diffusion Flame
The movement of molecules from an area of high concentration to an ara of low concentration
Fickās law of diffusion
Two major types of fuel air explosive that are encountered most commonly by fire investigator s
1 Mechanical explosions
2 Chemical Explosion
as explosion in which a high pressure gas creates internal pressure within a confining container and produces a purely physical reaction
Mechanical Explosive
the most common explosion related to fires is a chemical explosion that is also referred to as gas/ vapor explosion, a fuel air explosion, or a combustion explosion.
-high pressure gas is the result of exothermic reaction wherein
A- combustion reaction
B- decomposition reaction
C- rapid exothermic reaction
chemical explosion
3 Explain fire behavior as it relates to the four phases of fire growth, flashover, fire spread and fuel load.
1 Ignition Phase
2 Growth Phase,
3 Fully Developed,
4 Decay phase-fire begins to decline in intensity due to lack of fuel oxygen or heat (Fire suppressions Efforts)
-The transition stage in fire development when all combustible in the room reach ignition temperatures simultaneously. BC a room on fire
-Flashover
The amount of energy impacting a solid fuel surface necessary to gasify a unit mass of fuel
-referred to as (PYROLYSIS)
Breaking down fuels until they decompose and gasify. The gas ignite and burns
Heat of Gasification
- Fire will spread at the heat is transferred by methods of convection, conduction and radiation.
-Fire spread
-The consideration of fuel loads will answer the question of what is burning?
-Fuel Load
have a flash point of less than 100F
Flammable Liquid
Have a flash point of 100F or greater (additional energy required)
Combustible Liquid
Heat of combustion x area will tell u
Mass burn rate
Turbulent Flame
-Fame heights approaching approaching 1 foot less stable due to velocity of air entrainment
-Large eddies develop from air entrainment
Radiant heat transfer can account for up to ___ heat tranfer
50%
4 List and define two major types of fuel air explosion and the properties/ behaviors of common combustible gases.
1 Mechanical explosions
2 Chemical Explosion
Relatively uniform pushing
- Window frames tend to stay intact and are projected away from structure
- Greater damage away from point of initiation
- Subsonic blast wave
Fuel/ Air Signatures
Why Inv Fire scene
Need to bring to the Courtroom
- Never miss an opportunity to walk where a bad guy walked
- scene polygraph
what is the Scientific Method of a fire ( A systematic Approach)
Recognize the need Define the problem Collect Data Analyze Data Develop Hypotheses Test Hypotheses Select Final Hypothesis Make a determination
Scene Investigation steps
Arrival at scene use-determine legal authority
Security of fire scene= CS, limit access, overnight security
safety at the fire scene
Documentation
Origin and cause determination
Finish Sketches are
NOT TO SCALE
What is Examine the scene from the outside to inside
-Examine the scene from the area of least damage to the area of most damage
Systematic Approach Origin to inside
Why are fires investigated
To determine if a criminal act has occurred (arson)
To determine liability or responsibility (Civil)
To determine fire prevention (Public Safety)
Fuels are lighter than air (natural gas) will result in explosion damage in the upper portions of the structure: fuels that are heavier that air (LP) will result in damage that is in the lower portions of the structure= T or F
note
Artifacts left by the fire FP of the fire Noted and Documented Part of Data collection process Studied and tested
Fire Patterns
What are the two type of fire patterns
Fire Movements Patterns
Fire intensity patterns
Multiple origins -trailers -Pour patterns, Ignitable Liquids -Disabling fire protection system -Tampering with utilities -Unusual fuel loads or fuel configurations -Incendiary devices -crime concealment -
Incendiary Fire indicators
Accidental causes of fire
Electrical Heating equipment mechanical Cooking smoking candles Spontaneous heating Children
The intentional or unintentional destruction of evidence which would prohibit the interested parties from a fair examination of evidence
Spoliation
Common Fire causes
1 Improper careless use of smoking materials 2 Electrical causes 3 Cooking/ kitchen fire 4 Industrial 5 mechanical Failures 6 Natural 7 Open Flame 8 Negative corpus
What is intentionally ignited fore under circumstance in which the person knowns that the fire should not be ignited
Incendiary
- Accidental - cause that does not involve an intentional human act to ignite
- Incendiary - Cause that involves an intentional human act to ignite
- Undetermined- A proven cause that cannot be determined
Three fire cause determinations
- suspicious is a fire call
- fire burned too hot and fast
- this hole means something was poured low burn
- most damage always equal area of origin
- multiple origins means incendiary
- inverted v pattern means accelerant
- Depth of Char
Myths, Legends and pitfalls
-
Cause investigation
10 ID and explain the origin and cause of a fire in a burn cell during the fire scene practical Exercise (PE) by following the step of the systematic approach and by using team concept
-
9 - Spalling of concrete Crazing of glass Area of greatest damage= area of origin Rate of char analysis Alligatoring of wood Hot and fast fire Pour Pattern vs post flashover damage Melting of aluminum thresholds
Common Myths and Legends (False)
8 Accidental- cause that does not involve an intentional human act to ignite
Incendiary- A cause that involves an intentional human act to ignite
Undetermined- a proven cause that cannot be determined
-
7 what is
Common incendiary fire indicators
5 List and define the steps of the systematic approach to the origin and cause investigations of a fire and how it applies to the team approach at fire scene investigations.
Recognize the need Define the problem Collect Data Analyze Data Develop Hypotheses Test Hypotheses Select Final Hypothesis Make a determination
6 List and define common terms pertaining to direction and intensity of burn and fire patters such āVā patterns, lines of demarcation, char, protected areas, clean burn, calcination, pour patterns, and spalling
- V Patterns= up and out
- Hourglass=narrow down low then spread out at top
- Lines of Demarcation=soot and heat damage line around the building
- Char (Depth of Char)
- Pour Patterns vs Floor patterns
- Protected Areas
- Clean Burn
- Calcination of Gypsum
