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

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

6. Multiple Points of Origin Prove that they are separate & distinct not the result of fall down

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

8. 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 • Don’t 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

12. 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

14. Hourglass Pattern May be the result of an ignitable liquid or any other material that releases heat at a high rate

15. “Red Flags” After elimination of all accidental causes, use the “red flags” to assist in origin and cause

16. 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?

17. 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 owner’s/occupant’s story match the circumstances? • Did the fire occur during inclement weather? (delayed response or excuse for fire)

18. Electrical Sources of Ignition Ignition source may be electricity Rule out all other possible ignition sources

19. If you suspect electrical Do a careful examination of the electrical system

20. 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

21. Four Groups of Electrical Sources of Ignition • Aging electrical equipment • Improper use of approved equipment • Electrical accident • Improper installations

22. Aging Electrical Equipment • Deterioration • Worn out • Includes • electric motors • switches • appliance cords • extension cords

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

24. 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

25. 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

26. 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

27. 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

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

29. Electric Motor Malfunctions • Friction of motor belt • Overfusing or malfuction of overload protection devices • Improper mounting • Hazardous mounting • on a combustible surface

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

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

32. 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

33. Electronic Equip. Malfunction • Common ignition sources: • insulation failure of the electric cord • inadequate clearances • breakdown and shorting of internal components