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

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.

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.

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.

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.