Examples of Fire Patterns: Ignitable Liquid Pour Pattern
Annotated by Robert A. Corry
Director, Fire Investigation Specialist
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
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.
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
- 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
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.