CTA Report, Draft 1, ISP Review - US Chemical Safety and Hazard ...

• Physical marks (e.g., fire patterns) left by the fire.
• Physical debris and damage, which indicated the direction and relative force of the
explosions.
• Observations reported by persons who witnessed the fire or explosions, or who were aware of
conditions at the time.
7.1.1.1 Point of Origin
CSB confirmed the conclusions of ATF and the State Fire Marshal that the fire and initial explosion
originated at the line 405 oven. Based on eyewitness accounts and examination of physical evidence,
CSB determined that the initial explosion’s point of origin was likely in the aisle on the east side of the
line 405 oven, near the south end. A number of employees stated that they saw the initial flash at this
location.
The partially collapsed concrete block masonry firewall east of the oven also provided evidence of the
location of the initial explosion. A metal cabinet along the wall had been knocked over and was found
lying against the oven.
In contrast, the west side of the oven received only fire damage rather than explosion damage. Also,
burned resin deposits were on the exhaust hood located over the conveyor where the fiber mat enters the
oven. Rolls of facing and empty spindles were burned but otherwise intact. The metal ducts that
extended above the oven were warped and discolored—signs of extreme heat and external fire, but not
explosion damage.
CSB also examined the interior of the oven; virtually all the combustible material that likely had been
inside was burned away (Figure 13). In contrast, the interior of the ovens on lines 401, 402, and 403
contained accumulations of resin powder/fiberglass debris. The chain-driven oven flights for 405 were
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