Fire Cause Investigation Flashcards
Why do we investigate fires?
- It is the law as required by the International Fire Code
- To determine unsafe products and /or procedures that may be causing and creating a danger to the community
- To determine incendiary fires and investigate until the responsible party(ies) have been brought to prosecution
Definition of Fire according to Fire Cause class
• Fire is a rapid, self-sustaining oxidation process usually accompanied by the evolution of heat and light in varying intensities
Fire Triangle/fire tetrahedron
- Fire Triangle
a. Oxygen
b. Fuel
c. Heat - Fire Tetrahedron
a. Oxygen
b. Fuel
c. Heat
d. Uninhibited chemical chain reaction
Methods of heat transfer
a. Conduction
i. Transfer of heat by direct contact of one body to another
b. Convection
i. Transfer of heat by some circulating medium (either gas or liquid)
ii. Convection is the form of heat transfer which is most responsible for the spread of heat in structure fires
c. Radiation
i. Heat being transferred from one area to another without direct contact with the area, and without any circulating hot gases to help “bathe” the area in heat. It is heat in the form of energy which travels through space or materials as waves
Flashover according to fire cause class
a. Contained fire where exposed surfaces simultaneously ignite from thermal radiation
b. Stage of fire when room or other area becomes heated to the point when flames flash over the entire surface area
Backdraft according to fire cause class
a. An explosion or rapid burning of heated gases resulting from the introduction of oxygen when air is admitted into a building heavily charged by smoke form a fire that has depleted the oxygen content of the buildin
Fire stages according to fire cause class
a. Growth/Incipient 300-600 21% oxygen
b. Free Burning 1200-2000 18%
c. Smoldering 800-1000 13-15%
Combustion By-Products
a. Fire gases
b. Flame
c. Heat
d. Smoke
Point of origen
a. The place of the fire’s beginning
b. Normally, the fire cause will be found at, or very near, the point of origin
c. Fires often burn longer near the point of origin
d. Evidence of incendiarism is often recovered near the point of origin
e. Evidence of fire spread (or direction of fire travel) may be noted/ confirmed after locating the point of origin
f. The point of origin may confirm or contradict the stories of owners/ occupants/suspects
Fire Cause investigation is backwards why?
Investigator must usually work backwards in relation to the fire’s travel or spread, working toward the point of origin. For this reason, fire cause investigation is commonly referred to as a “Backward” investigation
What fire investigative stuff do we find on the outside of a structure?
i. Note areas of damage by heat and smoke
ii. Fire damage to building exterior
What are we looking for on the inside of a structure
i. Ceiling damage may help to locate point of origin
ii. Floor damage may help to locate point of origin
iii. Lowest level of burning
iv. Lack of soot (carbon) in a heavily burned area may indicate the area of origin
v. “V” Patterns
vi. Structural damage from fire as an indicator of fire’s travel
vii. Depth of charring as an indicator of fire’s travel and the point of origin
1. 1” for every 45 minutes in wood. (structural members) at approx.. 1400 F
viii. Flashover
ix. Multiple points of origin
What does fire cause look for in glass objects?
- Light staining .. limited fire or intense heat and/or rapid fire growth
- Heavy staining.. slow fire build up or remote distance from point of origin. (Exception- Heavy petroleum base in fire load)
xi. Glass- Cracking or crazing, Light bulbs
What does fire cause look for in melting stuff?
xii. Melting
1. Aluminum 1200 F
2. Copper 2000 F
3. Window Glass 900 F when exposed for 10 minutes
Is reconstructing the scene necessary?
xiii. Reconstruction Necessary to Properly Determine the Point of Origin
1. Locating the proper position of items within the fire scene
2. Identification and use of “protected areas”
3. Allows the investigator to more readily determine eh lowest level of burning, “V” patterns, and evaluate the fuel load and burning sequence within an area
Three elements of accidental fire cause
a. Three elements of fire
i. Heat source
ii. Fuel
iii. An “event” which brings together the heat source and the fuel
Heat sources
i. Chemical – exothermic, endothermic, pyrolysis, solution
ii. Electrical – resistance, induction, dilation, arching/sparking
iii. Mechanical – friction, compression
iv. Nuclear – explosion, radiation
Accidental fire includes
i. Acts of God
ii. Mechanical Malfunctions
iii. Carelessness
iv. Stupidity