Fire Investigation Flashcards
How do you collective debris with suspected volatile accelerants?
- Use metal cans, glass jars, or special nylon or polyester bags (e.g., Kapak)
- Do not fill completely – leave airspace
- Seal completely
- Label contents, source, location
- Keep cool
- Freeze if contains soil
- Do not use polyethylene containers
How do you collect clothing evidence?
- Air-dry and seal in clean paper bags unless volatiles are suspected
- If volatiles are suspected, seal in cans
- Refrigerate and transport to lab ASAP to minimize mold/mildew
How do you collect chemical evidence?
- Seal in glass vials with Teflon-lined caps
- Label all containers
- Document thoroughly via notes, sketches, and photos before
collection - Residues of chemical incendiaries are usually corrosive so should be
placed in glass jars with Teflon-lined lids or in Kapak bags
How do you collect fingerprint evidence?
- Seal in glass vials with Teflon-lined caps
- Label all containers
- Document thoroughly via notes, sketches, and photos before
collection - Residues of chemical incendiaries are usually corrosive so should be
placed in glass jars with Teflon-lined lids or in Kapak bags
How do you collect liquids?
Uncontaminated flammable liquids from the scene are often collected for
reference
– May be left in original container
– Could be transferred to clean sealable container
– Could be absorbed on to some material (e.g. cotton ball) and placed in a suitable airtight
container
* If liquid is present on concrete, how do you collect?
– Moisten area and spread adsorbent material
* Could be clay-type kitty litter, diatomaceous earth, or flour
* Let stand for 20 to 30 minutes then put into a clean metal can
* Critical is the cleanliness of the cans and tools used to collect the
adsorbent
What are comparison samples in fire investigation?
- help account for contributions made to the analytical results by the debris and substate materials
- unburnt carpet samples, wood etc.
What conditions must be present for a fire to occur?
- combustible fuel
- an oxidizer
- ignition source
- fuel and oxidizer must react in a self sustaining reaction
- removal of any of the four conditions required for fire results in extinguishment or failure of ignition
What is conduction?
- transfer of heat through a material by direct contact
- ignition is made easier with fuels with poor conductivity as heat is not being conducted away from application
What is convection?
the distrubution of heat by means of a circulating medium or the transfer of hear to or from a moving medium
What does convection do during a fire?
- this form of heat transfer accounts for most hear movement in a normal fire
- in fires the moving masses of hot materials are the gaseous products of combustion along with the surrounding air (which is also heated)
- these expand, become lighter and move upward at a rapid rate
What is radiation?
- all objects radiate some electromagnetic energy
- this energy does not need contact or a circulating medium to be imparted
What is radiation in a fire?
- aids fire spread across fuel surface without contact or circulating medium
- can be sufficient to bring combustible materials to ignition
What are general considerations of a fire scene investigation?
- Successful fire investigations start with proper attitude
– Open mind
– Care of evidence
– Adequate time, resources, expertise - Fire scenes are everything a good crime scene investigator would not like them
to be - Arson is a unique crime that destroys rather than creates evidence as it
progresses
Who must the investigator conduct interviews with at a fire scene?
- firefighters
- witnesses
What kind of search patterns are used in a fire search?
- anything that looks out of place should be checked
- aerial or overhead views
- most structure fires lend themselves to a spiral search pattern (outside in)
- large scenes (or fatal fire scenes) may require gridding to permit thorough searching
What do fire patterns indicate?
- direction of spread
- location of fuels
- location of ventilation sources
What are burn patterns?
created when applied heat fluxes are above the critical thresholds to scorch, melt, char or ignite a surface
what is a v-shape burn pattern?
A V-shape burn pattern refers to a specific type of burn pattern commonly seen in fire investigations or arson cases. It occurs when a flammable liquid is poured or splashed onto a surface and then ignited. When the liquid burns, it creates a distinct pattern resembling the shape of a V.
This pattern is created because the liquid spreads out in the direction it was poured due to gravity, forming a wider base where it was initially poured and narrowing as it travels away. When the liquid is ignited, the resulting flames follow this pattern, leaving a burn mark that resembles a V shape.
What is a u-shaped burn pattern?
This pattern is formed when a liquid is poured or pooled in a specific area and then ignited. As the liquid burns, the flames create a U-shaped pattern due to the distribution and movement of the liquid before ignition.
What is beveling and direction in burn patterns?
Edges and corners of items are easier to ignite and burn more
quickly
* This can induce beveling of edges when heat is applied to an item
* This predictable behavior can be used to re-create the direction of
fire gases
* Directional travel can produce cross-sectional beveling of exposed
wood elements, indicating the flow of hot gases around them
– Can be used to plot pointers or “arrows” of fire spread in a direction plan of
the building
– Vector analysis – combination of direction and intensity indicators
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What is heat level?
The demarcation (usually horizontal)
of fire damage revealed by the
charring, burning, or discolouration of
paint or wall coverings
Why are low burns on walls or burned floor materials important?
low burns on walls or floor materials serve as essential clues for fire investigators, guiding them in determining the fire’s origin, behavior, and potential causes.
