"V" Patterns + Inverted Cone Patterns + Hourglass Patterns = Confusion. Fire Findings, Vol. 3, Issue No. 1, Winter 1995.

Abstract: This article explains the various "V" patterns an investigator might come across. Most fire moves up an out creating a "V" pattern. Abnormal fires create inverted "v" patterns. Most investigators have associated inverted "V" patterns with accelerants. Section 4 of NFPA 921 states that any fuel source can cause inverse "V" patterns. When a fire burns against combustible wall, it creates an inverted "V" pattern. As the fire burns up and out it reaches the ceiling. Now the fire can no longer burn up, only out. This creates an hourglass pattern that consists of both a "V" pattern and an inverse "V" pattern. As the fire progresses, the hourglass pattern becomes a common "V" pattern. If the fire is stopped before the fire reaches the ceiling, an inverted "V" pattern may remain for fire investigators. This pattern is not an accurate indicator of an accelerant, or arson.

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