The document discusses determining the cause of fires by investigating the area of origin. It describes examining evidence on the exterior and interior of structures and identifying the first material ignited to reconstruct the ignition sequence. Fires can be classified as natural, accidental, or incendiary based on whether they were caused by natural events, mistakes, or intentionally. Once the origin and cause are identified, responsibility may need to be placed on persons or faulty products.

1. Fire Cause Chapter 13

2. Objectives Describe what needs to be done in conjunction with the search for the area of origin Describe evidence found on the exterior of a structure that indicates an explosion Describe the importance of identifying the first material ignited Describe the four different classifications of fire causes Describe identification of the product or person

3. Case Study Oil furnace was serviced by oil company Homeowner started furnace next day It filled the house with smoke and burnt a section of the basement Investigator discovered that furnace had not been properly serviced in over ten years, which resulted in the hostile fire

4. Case Study (cont’d.) Figure 13-1 The furnace in the area of origin. The wall adjacent to the furnace is burned clean. Figure 13-5 The access area to the heat exchange with the plate turned up out of the way. This area had allegedly been cleaned the day before, but soot and scale are evident, piled up at the face of the opening.

5. Introduction Knowledge of chemistry and science principles is an invaluable tool First vital necessity is locating the fire origin Might find evidence that will assist you in determining the cause of the fire Documenting is critical along the path to the fire origin Search for the cause must be done systematically using scientific methodology

6. Legal Issues Reason the fire service is allowed to stay on the fire scene is to handle the emergency and to identify the area of origin and the cause of the fire All portions of the structure should be examined Even those without damage If there is no connection to looking for extension of the fire, then it may constitute an illegal search

7. Legal Issues (cont’d.) If the investigator uncovers evidence that the fire may be incendiary in nature, the investigation changes focus It would be prudent for the investigator to: Place the scene under guard, keeping all out of the scene Approach the proper authority for a search warrant If evidence is out in the open and there is a chance that it may disappear or be damaged It is acceptable to document, collect, and preserve

8. Protecting the Scene Protect the scene using barrier tape and guards Not just in criminal cases: evidence for an accidental fire is just as crucial in a civil case

9. Exterior Examination Figure 13-7 A trailer of poured diesel fuel that leads from the kitchen, out the door, down the steps, across the backyard, and behind an aboveground pool.

10. Exterior Examination (cont’d.) Figure 13-8 An evidence tag sitting on top of a bucket that protects a footprint in the soft earth.

11. Interior Examination What to search for and document Investigator must search all rooms and areas of the structure Search of the structure for extension of the fire and to eliminate any potential fuel or ignition sources

12. Accidental Indicators The process of elimination is just as important as confirming a potential correlation between the clues Presence of smoking materials and burn marks from cigarettes is evidence but is not proof by itself Damaged electrical wires and improper electrical connections in the undamaged areas of the structure is not proof of fire cause but will require investigators closely examine electrical equipment in area of origin

13. Incendiary Indicators Burn patterns, such as pooling patterns and sharp line of demarcations may be indicative of ignitable liquids Common household items stacked and placed in the structure to act as trailers Mere presence of an ignitable liquid pattern or even a positive sample is not an indication by itself of an incendiary nature

14. Source and Form of Heat of Ignition Figure 13-9 Careful examination of the scene revealed melted plastic that was the residue of a 1-gallon milk jug that contained gasoline at the time of the fire.

15. First Material Ignited The first material ignited tells the story of what happened First material ignited has a form or shape Some items need a little more clarification Plastics take many shapes and sizes and have varying characteristics

16. Ignition Sequence When a heat source and a fuel do come together, there can be ignition You must apply science that will prove that the available heat source was sufficient to ignite that specific first material ignited Sometimes the ignition sequence is so obvious that verification need not be documented Wooden kitchen match dropped onto crumpled writing paper

17. Ignition Sequence (cont’d.) If there is any doubt, NFPA texts and documents can verify the ignition temperature of various materials Final hypothesis should identify and explain the heat source in detail Should also identify the first material to be ignited Explain why the two were in close proximity

18. Elimination of All Other Causes Figure 13-10 Tag left on the gas supply line outside the structure showing that the liquid propane gas bottles had been removed prior to the fire. If there is no date on the tag, the gas provider can give exact dates of removal and reasons why.

19. Classification of Fire Cause All fires are considered accidental in nature until proven otherwise Natural Fire was not started by the actions of a human Lightning, lava flows, or flooding that creates electrical shorts Accidental Someone made a mistake and some action of a human resulted in the heat source coming in contact with the first material ignited

20. Classification of Fire Cause (cont’d.) Incendiary Many fires are intentionally set, but that does not make them incendiary Setting fire to logs in a fireplace Key difference between these fires and incendiary fires is the intent Key component of this frame of mind is malice Undetermined No matter how good an investigator’s skills, there are fires that will go undetermined

21. Determining Responsibility Once the origin has been located, you have a place to look for the cause Product Product failure as a result of design Product failure as a result of manufacturing Product is proper, but the instructions were lacking Person or persons Deterrence is a tool in the fire prevention toolbox

22. Summary It is essential to determine the area of origin The cause of the fire can fall in the category of natural, accidental, incendiary, or undetermined Once the area of origin and cause have been confirmed, then it may be necessary to identify the persons or things responsible for the fire If person involved, investigator must determine whether there was malice