Abstract: At approximately 3:00 a.m. on January 5, 1991, Employees #1 and #2, of Willamette Industries, Korpine Division, were trying to thaw the throat of the air lock to the star feeder at the bottom of the cyclone for the green dryer system. A space heater was placed on the east side of the air lock casing and had been there since the previous shift, approximately 7 hours. Employee #1 removed the 16 in. by 24 in. inspection plate from the east side of the air lock casing and found that material had accumulated to the top of the opening. When the plate was removed, the negative air inside the cyclone started to dissipate the material at the opening back into the system. After about a minute, an explosion occurred, burning Employee #1, who was standing directly in front of the opening, over 60 percent of his body. He died at 11:43 a.m. on January 6, 1991, at Emmanuel Hospital. While trying to aid Employee #1, Employee #2 sustained 2nd-degree burns to his hands and head.