Arson,Fire and Explosive Investigations Flashcards
1
Q
Flash and Ignition Points and Pyrolysis
A
Flash: lowest temp that a liquid gives off a combustible vapour
Ignition: lowest temp that a vapour can be ignited
Pyrolisis: decomposition of gas with heat exposure
2
Q
Flammable Range, Glowing and Spontaneous Combustion
A
Flammable: range that will support combustion
Glowing: without a flame
Spontaneous: due to natural heating
3
Q
Point of Ignition
A
- can be determined by pattern (upward)
4
Q
Arson Evidence
A
- Incendiary: scene debris, burn characteristics, accelerant
- Motive: vandalism, thrill, insurance, concealment
- Document and collect in air tight paint cans
- collect a contaminated, uncontaminated and control sample
5
Q
Explosions
A
- sudden buildup of expanding gas pressure
- low order: low rate of conversion, heat ignition (pyrotechnics)
- High-order: rapid conversion, detonation device (dynamite)
6
Q
Scene Search
A
- detonation point: should have enough residue for ID, microtagants
- hot zone: highest damage
- warm zone: end of evidence + half that distance
- cold zone: command post, family
7
Q
evidence collection
A
- collect in nylon arson bags or paint cans
- items that can’t be collected are swabbed and placed in glass jars
8
Q
Chemistry of Fire
A
- Exothermic rapid oxidation reaction
- oxidation: more energy released than needed to react
- fuels broken down in gas state and consumed
- CO is a by-product
9
Q
Flammable v. Combustible
A
Flammable: less than 60 degrees
Combustible: greater than 60 degrees
10
Q
Methods of Heat production and transfer
A
- production: chemical, electrical, mechanical, compression, nuclear
- transfer: conduction (direct), convention (circulation), radiation (waves)
11
Q
Phases of progression
A
- incipient: earliest, seconds to hours
- emergent smoldering: pronounced combustion products
- free burning: increased intensity and rate of burning, increases with every 18 degree Fahrenheit increase
- oxygen regulated smoldering: oxygen depleted, heavy smoke
12
Q
potential indicators of arson
A
- accelerant, incendiary devices, ignition devices
- liquids are rarely fully consumed in a fire
13
Q
lab recovery of flammable residues
A
- heated in a airtight container, vapour removed with a syringe and injected in a chromatograph
- or charcoal strip in container, washed with solvent to remove vapour and placed in a chromatograph
14
Q
Gas Chromatograph
A
- separates hydrocarbon components and produces a pattern specific to a petroleum
15
Q
Ion mobility spectrometer
A
- sample bombarded with radioactive nickel isotopes, separated, characterized by movement through the field
