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
Misrepresentation of fire causes
i. Owners and /or occupants will sometimes misrepresent accidental fires because:
1. May think insurance will not pay off
2. May be embarrassed
3. Hope fire department will find another cause
4. Afraid of being charged for fire department response
5. Parents trying to cover for juveniles or adult children trying to cover for parents
Accidental fire causes sources
i. Heating equipment
ii. Smoking
iii. Flammable/Combustible liquids
iv. Spontaneous heating
v. Fireworks/ Explosives
vi. Lightning
vii. Low temperature ignition and accidental fires
viii. Cooking equipment
ix. Electrical equipment
x. Open flames/ Sparks
xi. Gas fires/ Explosions
xii. Dust explosions
xiii. Wild Land fires
Incendiary fire indicators
ALL of them…
i. Multiple fires
ii. Flammable accelerants
iii. Structural damage prior to fire
iv. Absence of all accidental fire causes
v. Removal of contents prior to the fire
vi. Major appliances removed prior to the fire
vii. Trailers
viii. Plants
ix. Common equipment/appliances
x. Absence of personal items/ important papers
xi. Location of the fire
xii. Evidence of other crimes in the structure
xiii. Unnatural fire spread, excessive fire damage, or evidence of extreme heat
xiv. Entry of fire companies blocked or view into structure blocked
xv. Injuries to occupants
xvi. Inappropriate period of time between exit of occupant and fire
xvii. Pre-burned contents of second fire in same structure
xviii. Presence of burned or unburned fuel near point of origin
xix. Fires occurring on holidays or weekends
xx. Time of day
xxi. Water heater fires or fires where a convenient heat source is available
xxii. Fires during renovations
xxiii. Reported activities of owners/ occupants
xxiv. Statements of owners/occupants
Incendiary fire indicators - fire only
- Multiple fires
- Flammable accelerants
- Trailers
- Plants
- Location of the fire
- Pre-burned contents of second fire in same structure
- Presence of burned or unburned fuel near point of origin
Incendiary fire indicators - people only
- Evidence of other crimes in the structure
- Unnatural fire spread, excessive fire damage, or evidence of extreme heat
- Injuries to occupants
- Inappropriate period of time between exit of occupant and fire
- Reported activities of owners/ occupants
- Statements of owners/occupants
Incendiary fire indicators - structure only
- Structural damage prior to fire
- Entry of fire companies blocked or view into structure blocked
- Fires during renovations
- Water heater fires or fires where a convenient heat source is available