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Forensic Science: Fire Investigation

Chemistry35 CardsCreated 4 months ago

This deck covers key concepts in fire investigation, including the chemistry of fire, causes of fires, and methods used in forensic analysis to determine the origin and cause of fires.

What does the chemical reaction of fire produce?

heat and light
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Key Terms

Term
Definition
What does the chemical reaction of fire produce?
heat and light
Define what is the ignition point?
The ignition point is where a burst of heat and light is produce. = flame
Define combustion?
When heat changes the state or shape of an object
Name the 3 things that are contained within the fire triangle?
oxygen, heat, fuel
The more oxygen allows the fire to be more what?
The more oxygen the fire has the more fierce and intense the flame will then become. Allows the flame to keep ablaze
Name a few basic fuels?
wood, paper, dry grasses, coal, petroloil

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TermDefinition
What does the chemical reaction of fire produce?
heat and light
Define what is the ignition point?
The ignition point is where a burst of heat and light is produce. = flame
Define combustion?
When heat changes the state or shape of an object
Name the 3 things that are contained within the fire triangle?
oxygen, heat, fuel
The more oxygen allows the fire to be more what?
The more oxygen the fire has the more fierce and intense the flame will then become. Allows the flame to keep ablaze
Name a few basic fuels?
wood, paper, dry grasses, coal, petroloil
defin ; ignition
The initial energy required to start the fire
defin; Heat
This is the factor that controls the fire spread
What is preheating?
The period time in which the fuel is being heated
What is Radiation?
This is when the heat is transferred to the fuel via heat waves and rays .= fuel to heat up and catch fire
What is convection?
When the air becomes lighter when it is warm there rises to the highest point to cooler air warms that up and rises even more and so on
What is conduction?
Heat directly transferred from the fuel to the source
Name 3 causes of how a fire can start?
Electricity, Chemical leakages, Friction
Name one way of how an electric fire can start?
1/ overload of electrical circuits
Chemical fires
Through flammable chemicals i.e. Turpentine, insect, paint, sprays
What is smouldering ignition source?
When something hasn't been but out properly and just smoulders once it is exposed to enough oxygen it will relight
What are premixed flames?
An incipient flame in ignition of solids or liquids before diffusion flame emerges i.e. petrol engine ( spark ignition )
spontaneous combustion
chemical reaction takes place causing the item i.e. hay stack heating it up enough to ignite
Why do we investigate fires?
1/ establish cause and effect, 2/ identify to reduce future appearance, 3/ help in operational decisions and public educations
Name the main objectives of fire investigation
where, how, who, what, when, carbon monoxide poisoning
Name a few laboratory examinations?
Flammable liquid analysis, liquid comparison, burning test, appliance examination, devices, computer techniques
Is forensic fire examination and opinionated science?
YES , due to most fire after testing a burning things you can confidently assume
'Every fire scene must be considered as a possible crime scene until proven otherwise'
Kirks fire investigation
Main considerations when going in to a fire scene?
safety, control and security, scene preservation, cooperation, continuity of evidence
Safety equipment used?
hard hat, overalls, steel -toe-boots, debris gloves, dust mask
State some Dangers within a fire scene?
Changes in weather may effect the scene, affects of fire fighting, gas + electical supplies, roofs,glass, walls , floors - weakened, Asbestos / toxins
' A fire or explosion investigation is a complex endeavour involving both art and science'
NFPA 921
what needs to be done at the scene?
documentation, photos, video, audio commentary, name of witness
What are the characteristics of a point of origin?
low burning, V pattern, deeper chairing of wood, material distortion, smoke staining
Flash over
produces consistent burning over the whole top of the room
Burning of flamble liquids will leave what?
Trails, uniform burning, may be flash over
What are the indication of an arson fire?
accelerate present, elimination of natural causes, trail, multiple origin points
soot
fine black particles which are mainly carbon, can have sooty flame
long stress crack across in glass indicate what?
rapid hit
Cobweb in glass indicates what?
impact i.e. smashing