The bag dump station was positioned in the doorway of the pre-mix room. An overhead rollup service door was installed for access to the pre-mix room. At the time of the incident, the CSB found that the rollup service door was chained into a fixed rolled-up position to provide easier entry into the room. Witness accounts from plant employees and contractors indicated that Gilsonite dust generated from the bag dumping operation often accumulated around the facility but particularly on flat surfaces. US Ink did not provide an effective means of containing fugitive dust at the bag dumping station because emptied bags were often stacked alongside the bag dump, which in turn lofted dust into the air.