Abstract: On September 1, 1990, Employees #1 and #2, cosmetology instructors, arrived for work at Mitchell's Hairstyling Academy at approximately 7:30 a.m. and 7:40 a.m., respectively. The instructors followed normal opening procedures, which consisted of unlocking the front and back doors, turning on all the lights in the salon and classroom, and completing office duties in the instructor's office. Cosmetology students arrived at the academy from approximately 8:00 to 8:20 a.m. After roll call, at approximately 8:30 a.m., the students went to their assigned booth and began working on their clients' hair. The instructors offered guidance to students throughout the salon and classroom at different booths, as needed. The air conditioning system was on. From approximately 9:30 to 11:30 a.m., the majority of students and Employees #1 and #2 experienced headaches. From approximately 11:30 a.m. to 1:00 p.m., the symptoms progressed to dizziness, nausea, vomiting, and weakness. From approximately 1:00 p.m. to 2:00 p.m., Employee #1 began to tell the students to finish up their work and go home. At approximately 2:15 p.m., Employee #2 was picked up by her husband and taken home. At approximately 3:15 p.m., everyone else was leaving the academy, including Employee #1. At approximately 3:55 p.m., 5:47 p.m., and 6:19 p.m., a student, and Employees #1 and #2 were admitted (respectively) to the Wake County Medical Center Emergency Room. Arterial blood was drawn from each patient within 30 minutes to 1 hour after their admission. The following carbon monoxide (CO) exposure levels were calculated from the carboxyhemoglobin (COHb) results: Employee #1- 69 ppm CO, 10.9 percent COHb; Employee #2- 38 ppm CO, 6.3 percent COHb; student- 80 ppm CO, 12.5 percent COHb. Employees #1 and #2 were released the same day. The student stayed overnight. The carbon monoxide exposure resulted from a propane-fueled floor buffer (Pioneer/Eclipse 2000) that had been used to dry buff the floors in the salon and classroom the previous night. The cleaning crew had buffed approximately 4,000 sq ft of the floors throughout the approximately 5,000 sq ft building for approximately 1 1/2 hours. Excessive carbon monoxide levels were generated as a result of inadequate ventilation while buffing. There was no fresh air intake system on the air handling unit for the building.