Abstract: On May 4, 2007, Employee #1, was etching aluminum castings in an acid solution containing approximately 3 units of hydrofluoric acid and 30 units of nitric acid. The acid solution and etching procedure was performed in a drum with no local exhaust ventilation. A chemical reaction ensued, resulting in a significant release of orange and brown fume in the work area and possibly a spill. Management was alerted to the area and got the reaction under control. The employee did not complain of injury or adverse health symptoms and continued working for approximately three hours. Employee #1 clocked out and left work before his shift ended without notifying management. Later that evening, St. Francis Hospital notified the Fire Department that they were treating Employee #1 for acid exposure and requested the material safety data sheets (MSDS) for the acid solution. The employee was transferred to Loyola Hospital in critical condition.