Abstract: At approximately 12:50 p.m. on September 25, 1993, Employee #1, a plater/maintenance worker for K&L Plating Company, was assisting Employee #2 in cleaning wastewater treatment tanks. Employee #2 entered tank G to remove sludge and water from its bottom using a wet/dry vacuum cleaner with hose and nozzle attachments. The vacuum had been previously used to clean a liquid acid/cyanide solution. The atmosphere inside tank G had not been tested for contaminants or oxygen content prior to the employee's entry. Employee #2 was overcome by cyanide fumes. Employee #1 entered the tank in an attempt to rescue Employee #2, but was himself overcome by the fumes. Employee #1 died and Employees #2 and #3 sustained serious injuries from their exposure to the fumes. Several other employees were overcome when they assisted in the rescue operation. Neither Employee #1 nor #2 were wearing the proper respirator or protective equipment when they entered tank G. If the employees were properly equipped and trained, the accident would have been prevented. Willful serious violation of 8CCR 5144 (a), 5159(a)(4), 5159(b)(1), 5158(c), 5157(b), and serious violation of 8CCR 3203(a)(4), 5159(a)(5), 5144(f)(1), 5194(f)(1), are determined to be accident related.