Determining Fire Cause

1
Determining Fire Cause
2
Determine Area of Origin Point of Origin

• Before attempting to determine a cause

3
Fire Cause

• Results of an event that brought together the
  heat, fuel, and oxidizer that resulted in a fire

4
Types of Fire Cause

• Accidental Fires
• may originate with or without the aid of a human
  being
• Incendiary Fires
• are those that are maliciously or deliberately
  ignited

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Incendiary Fires

• Watch for key indicators
• when you observe these indicators call for fire
  marshal immediately
• take steps to preserve evidence

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Multiple Points of Origin

• Prove that they are separate distinct
• not the result of fall down

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Trailers

• An ignitable material used to spread fire
• usually leaves char or burn patterns
• may be used with an incendiary device

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Incendiary Device

• Designed used to start a fire
• Most leave evidence
• especially metal parts
• More than one device may be used
• Sometimes faulty ones can be found

9
Ignitable Liquid Patterns

• Irregular damage on floor may indicate
• Can be created by carpet, high fuel loads
  ventilation
• Liquids flow to lowest point
• Inspect corners base of walls for accumulation

10
Low Levels of Charring

• Indicate high amounts of heat at low levels
• May indicate ignitable liquids
• Dont jump to conclusions
• May be result of firefighting tactics, flashover,
  or ventilation
• Consider low burn with all other information

11
Concrete Spalling

• Caused by high heat moisture in concrete
• New concrete spalls more than old
• Can indicate ignitable liquids
• Consider all information when viewing spalling

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Inverted V-Patterns

• May indicate ignitable liquids
• Narrower at the apex (top) than at base
• Found on walls originate at floor
• May result from pooled ignitable liquids
• Can result from fall down, etc.
• Rule out all possibilities first

13
Hourglass Patterns

• Formed as a result of air movement from the side
  of the fire, cooling the wall surface where air
  enters the flame zone

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Hourglass Pattern

• May be the result of an ignitable liquid
• or
• any other material that releases heat at a high
  rate

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Red Flags

• After elimination of all accidental causes, use
  the red flags to assist in origin and cause

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Red Flag Questions

• Are contents moved or out of place?
• Is there an absence of personal items?
• Is there evidence of other crimes in the
  structure?
• Was the second fire in the same structure?
• Was there structural damage before the fire?

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Red Flags Cont.

• Was the fire department access blocked?
• Did the fire occur at an unusual time of day?
• Were there signs of forced entry?
• Does the owners/occupants story match the
  circumstances?
• Did the fire occur during inclement weather?
  (delayed response or excuse for fire)

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Electrical Sources of Ignition

• Ignition source may be electricity
• Rule out all other possible ignition sources

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If you suspect electrical

• Do a careful examination of the electrical system

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Interview Occupants

• Any problems before the fire?
• Lights dimming
• Appliances worked intermittently
• Television pictures contracted
• Receptacle plates were warm
• Wiring could have provided an ignition course

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Four Groups of Electrical Sources of Ignition

• Aging electrical equipment
• Improper use of approved equipment
• Electrical accident
• Improper installations

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Aging Electrical Equipment

• Deterioration
• Worn out
• Includes
• electric motors
• switches
• appliance cords
• extension cords

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Improper Use

• Use other than its intended purpose
• Examples
• Using heating appliances for drying items such as
  clothing
• Using undersized extension cords

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Electrical Accident

• Result of unexpected happening by persons using
  equipment
• Examples
• Electrical shorts in the electrical panel due to
  tools arcing
• Nails driven through wiring
• Unintentional physical damage

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Improper Installation

• Installation not in compliance with electrical
  code
• Examples
• improper splicing of wires
• uncovered junction boxes
• electrical motor installed without required over
  protection devices

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ElectricalOverload/Short Circuit

• A fire resulting from an electrical overload or
  short circuit can start any where in the building
  where there is electricity
• ex electrical panel, fuse boxes, breakers,
  wiring, appliances

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Electrical Overload

• Too much current flows through a wire or other
  conductor
• Fuses circuit breakers are over-current devices
  that automatically open or break the circuit when
  current is above safe levels

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Short Circuit

• Contact between two conductors unintentionally
  occurs
• Look for signs of arcing, beading and splattered
  metal
• Temperatures produced by arcing
• 2,000F - 7,000F

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Electric Motor Malfunctions

• Friction of motor belt
• Overfusing or malfuction of overload protection
  devices
• Improper mounting
• Hazardous mounting
• on a combustible surface

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Light Fixtures Bulbs

• Ballast transformers in fluorescent lights
• maybe an ignition source
• Transformers are designed to operate
• continuously at 194F
• Heat may melt or vaporize transformer contents
• Light bulbs
• contacting combustibles

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Aluminum Wiring

• Aluminum wire attached to a copper or brass
  terminal may eventually cause the connector wire
  to loosen, increasing resistance and producing
  heat

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Electrical Appliance Malfunction

• Clothes irons, coffee pots, toasters, deep
  fryers, frying pans
• Malfunction of the thermal control or thermostat
  contact points
• Clothes dryers
• high limit control or cycling thermostat
• accumulated lint ignited during normal operation

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Electronic Equip. Malfunction

• Common ignition sources
• insulation failure of the electric cord
• inadequate clearances
• breakdown and shorting of internal components