FIRE AND EXPLOSION INVESTIGATION LECT 2. Flashcards
What is a Fire?
This is the rapid oxidation of a material in the exothermic chemical process of combustion, releasing heat, light, and various reaction products.
What is Arson?
Arson is the crime of intentionally and maliciously setting fire to buildings, wildland areas, vehicles or other property with the intent to cause damage.
How can arson be distinguished from other causes such as spontaneous combustion and natural wildfires?
Arson often involves fires deliberately set to the property of another or to one’s own property as to collect insurance compensation.
While investigating a wildfire the investigator must :
- Be aware of areas of the fire that are still burning
- keep Incident Command apprised of his/her location at all times
- never enter an area without an avenue of escape
- constantly re-assess the safety conditions based on changes in
the fire - remain alert for smoldering and the potential for rekindle
- monitor the weather, especially wind changes, and how it
changes the situation - be careful when disturbing fire debris. If the underlying material
layers are still hot, moving the debris around can expose the
heated material to oxygen, causing it to combust. - Remain alert for falling debris from damaged trees and hillsides
- always wear proper safety gear, as defined by NFPA 1977, NFPA
1500 and OSHA
How to determine the area and point of origin of a fire?
- Interviewing witnesses and fire fighters
- Examine the exterior
3.Examine the interior - Analyse the information
What is the area of origin?
geographical location of where the fire started (room, floor)
What is the point of determine?
specific location of fire (point of ignition)
What are elementary rules of fires?
- Fires spread upwards and outwards (look for Vpatterns)
- Fires need fuel and oxygen to continue
- Intensity will depend on the amounts and types of combustible materials
- The fire will rise faster as it gets hotter (look different temperature conditions)
- The spread will be influenced by air currents, walls, stairways etc.
- Falling debris and actions by fire fighters will also have an effect.
What is char?
Char is material composed of carbon that has been burned and has a blackened appearance.
What is the V-pattern?
V-pattern may indicate point of origin, but not necessarily of initial point of origin (may be a secondary fire by drop down or radiation).
What are heat shadows?
These occur when heavy furniture shields part of the wall; can help determine the origin point.
What direction does glass melts when heated?
Light bulbs tend to melt to toward the heat sources, so the “direction of melt” can indicate the direction of the fire.
What depends on the damage of glass?
The extent of exposure during the fire.
What does undamaged/different conditioned glass on the floor indicate?
Glass lying on the ground or floor in a different condition than glass remaining in the pane may indicate breakage before the fire.
What are the conditions of the floor when compared to the ceilings?
Because of the normal upward movement of heat and fire, floors are usually damaged much less than ceilings, and floor damage could be a good indicator of area of origin.
What is Spalling?
Spalling (chipping or breaking away) of concrete is indicative of high temperatures and could be indicative of the use of fire accelerants.
How can spalling indicate presence of accelerants?
Analysis of concrete samples from areas of spalling may indicate/confirm the presence of accelerants.
What indicate trail patterns on floor?
Trail patterns on floor indicative of accelerants.
What are the three basic elements of arson?
- There is a burning of property
- The burning is incendiary in origin
- The fire has be shown to be started with malice, with intent to destroy.
Signs of incendiary fires (arson) include:
- Multiple points of origin
- Evidence of incendiary devices
- Signs of ignitable liquids
- Low levels of charring
- Hour glass and/or inverted V-patterns
What are evidence of incendiary devices?
- Metal parts of electrical devices such as timers often found in fire debris
- Metal parts of lighters or even staples of match books or empty match boxes can remain and be found in fire debris.
- The upward spread of the fire can mean combustible materials (such as empty match boxes) are not fully destroyed in the fire.
What are signs of ignitable liquids?
- Ignitable liquids will flow to the lowest point and can soak into materials.
- Unburned materials showing signs of accelerants should be collected in nylon bags for analysis by gas chromatography in the laboratory.
- Ignitable liquids will produce pronounced (and irregular) damage to the floor area.
4 … but beware as the damage could have resulted from “concentrated” fuel loads subject to good ventilation
What does low levels of charring may indicate?
Low levels of charring may indicate intensive heat at low levels, characteristic of the presence of ignitable liquids.
What does a hourglass pattern indicate?
A hourglass pattern may result from the use of ignitable liquid … effectively resulting from a combination of a normal V and an inverted V.
What indicates that ignitable liquid was poured on the floor?*
The base of the inverted V will be on the floor ,where the ignitable liquid has been poured, and will spread up the wall to the point of the inverted V.
Questions to ask when there is a body on scene?
- Are the remains human? - assume this to be the case unless there is evidence to the contrary.
- Who is the victim? – personal effects may help but dental records tend to be most useful.
- What was the cause and manner of death?
- Was the person alive and conscious at the time of the fire? carbon monoxide levels, indications of asphyxiation, smoke inhalation are pointers.
- Was the death due to the fire? – if not alive at start of fire then others causes come into play and need evaluating from post mortem evidence/examination
