Abstract: Employees #1 and #2, a leadman and a trainee, were engaged in the normal start-up operation of a sunflower oil extraction process unit. An extractor vessel was circulating and heating liquid hexane solvent. The hexane was flowing in a closed loop while other process equipment was being prepared for normal operations. A downstream vessel known as a desolventizer/toaster had not been purged to eliminate oxygen. It had been heated using high temperature steam, which caused the residual solid product cake to smolder. Hexane vapors released from the extractor vessel had entered the desolventizer/toaster vessel and were ignited by the smoldering residue, resulting in an explosion. Employees #1 and #2, who were standing on a catwalk near the desolventizer/toaster vessel, were struck by a flame ball and hospitalized with burn injuries.