Abstract: Employee #1 was filling 55 gallon drums with motor oil when he was overcome by vapors emanating from supposedly empty 5 gallon drums which were in a semi-trailer approximately 40 ft away. Employee #2 was working in the area and saw that Employee #1 was having some sort of convulsion. Employee #2 pulled Employee #1 from the area, and Employees #3 and #4 were notified and went to investigate. A strong chemical odor was evident, so they exited the building and phoned for emergency personnel. All four employees experienced headaches, dry mouths, and stomach pains. Employees #1 and #2 were hospitalized for two days; Employees #3 and #4 were treated and released. The building remained evacuated until the evening of the incident. The chemical was not identified.