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Examples of Fire Patterns: Ignitable Liquid Pour Pattern

Annotated by Robert A. Corry
Director, Fire Investigation Specialist
American Re-Insurance

The following indicators were present when this pattern was excavated that helped to establish that this pattern resulted from an ignitable liquid pour and was not caused by falling, burning debris or from a flashover effect:

1. Structural damage inconsistent with fire loading.

2. Intermixed light, moderate, and intense floor burn patterns in puddle or trailer shapes that correspond to the original shape of the ignitable liquid pool on a tight, nonporous linoleum floor.

3. Localized "gapping" of wood or vinyl floor seams within the pour burn pattern, which may be caused by a liquid accelerant burning inside the seam. These indicators were identified at the base of the all on the top right where the burn pattern intersected with a wall and again where the floor burn pattern intersected with the threshold.

4. Increased burn damage pattern at the bottom of the wall in the pour pattern area.

5. Burn patterns beneath the threshold boards and floor moldings where the burn pattern intersected but not elsewhere in that area.

6. Wall burn patterns running from the floor seam up and appearing in corners.

7. Sharp line of char demarcation in a cross-section of wood stud, or a sharp line of calcination (color change) in plaster or drywall, indicating a rapid (rather than smoldering) heat buildup.

8. An empty one-gallon mineral spirits (paint thinner) container with no cap was discovered in another room at the end of the burn pattern.

Additional points:

1. In addition, this floor burn pattern formed in a continuous "pour pattern" fashion along the low point on the linoleum floor where a "wear pattern" had formed from persistent foot traffic over the 70 years of the building's existence.

  • Investigators later helped establish this "wear pattern" by pouring fresh water onto the linoleum floor (once documentation and evidence collection were completed). The water collected in the same area where the burn pattern was present.

2. This particular pattern represents an "intense burn" where the floor surface was physically damaged rather than merely scorched or sooted.

  • Accelerants with high vapor pressure, such as alcohol or acetone, tend to "flash and scorch" a surface, whereas accelerants with higher boiling components, such as gasoline, tend to "wick, melt, and burn," leaving stronger patterns.
  • In this case, samples were taken from the pattern intersection with the threshold board at the bottom center and the floor molding and threshold board at the top right and center revealed the presence of a residue of "mineral spirits" (paint thinner).
  • Comparison samples taken from unburned molding (at the extreme left of the photograph) plus adjacent linoleum revealed no presence of ignitable liquid residue.

3. A witness who was in an adjoining, third floor apartment stated that she felt andheard a "boom" after which she went to her corridor door and opened it slightly. She watched the apartment building owner exit from the apartment where the fire began, close the door and go out a fire exit. Seconds later, she described "light smoke that quickly became dark smoke" pushing out from the door seams across the hall. The building's smoke alarm went off and she quickly exited the building. She also said that within two minutes of making these observations, she went to the landlord and told him that there was smoke coming from the apartment. She later testified that he said nothing and failed to go and check to situation.

These photographs and annotations are provided to illustrate the burn pattern indicated. They are examples only, not models.
Photograph courtesy of Robert A. Corry.

Reprinted with permission from the author.

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