On Tuesday morning, October 9, 2012, black ink production continued, with batches beingrun in all three mixers. When the batch in T-306 was completed, the pre-mix room operatoremptied the tank. The operator left for lunch at about noon and returned to the pre-mixroom at about 12:30 pm EST. At that time, a new ink batch was started in T 306. At about1:00 pm, the pre-mix room operator was loading Gilsonite into the bag dump station(Figure 1) when he heard a strange (squealing)25 noise from T-206. Because of the odd noise,the operator went to the control room to check the mixing tank temperature and speed toconfirm that the equipment was working properly. As he left the control room, he saw aflash fire originating from the bag dump station where he had just been working. Withoutshutting down the mixing operation and the dust collection system from the control panelsnear the pre-mix room, the operator immediately proceeded to his supervisor’s office to alerthim of the fire, moving away from the pre-mix room. At about the same time, other workersheard a loud thump that shook the building.