Abstract
Fifteen employees became ill with headaches, nausea, and vomiting due to chemical poisoning at a Vermont community hospital on January 3, 1980. An epidemiologic and environmental investigation was conducted to determine the source of the illness. The investigation discovered that the vapors of a chemical called xylene, which had previously been disposed of down a drain, were drawn back through the sewer into specific work areas. These vapors were determined to be the most likely cause of the illnesses. This outbreak investigation was used to create an exercise that has been used in a variety of teaching settings.