Abstract: The employer is a non-profit privately owned community health clinic that employs approximately 300 employees. During the last week of November 2000 and the first week of December 2000, several employees began experiencing health symptoms such as skin/scalp rash, itching, chest pain, running eyes/nose, elevated blood pressure, respiratory irritation, tightness of throat, etc. Initially, the situation was treated as a hazardous materials emergency response incident and the workplace was evacuated of employees. Approximately one third of the buildings occupants had been affected by the unknown contaminant(s), and ten of those were hospitalized for medical observation and treatment. The building was completely cleaned and no known cause was found in the building. The occupants were allowed back in building over the next few weeks. The likely cause of the incident was poison oak contamination from outdoor burning.