Abstract: At approximately 12:36 p.m. on April 15, 1988, employees of Amoco Oil Company, Consolidated Fabricators and Constructors, Inc., Viking Engineering Company, and PDQ Company were performing maintenance on the MEK dewaxing unit in the Amoco Oil Refinery. Employees #19 through #23 were removing steel deck plate from the facility and installing steel grate flooring using air arc equipment. The flammable material inside the filter unit had not been fully purged before the cutting and welding was performed. The filter units contained wax removed from waxy oil that was processed through the G-3 filter unit. The wax contained MEK and toluene. The welding and cutting operations ignited flammable vapors from the G-3 filter unit, which resulted in an explosion. Employees #1 through #17 and #19 through #22 sustained disabling injuries, second- and third-degree burns, fractures to arms and legs, and abrasions. Employees #19, #20, #21, and #22 were hospitalized with second- and third-degree burns.