Abstract: At 12:30 p.m. on a Wednesday, the busiest day of the work week, employees began experiencing symptoms. Two propane forklifts and an electric forklift were in use. A propane forklift had been out-of-service early in the day for radiation repair and had been returned to service at approximately 10:30 a.m. As the afternoon progressed, the number of symptomatic employees increased, causing the employer to suspect carbon monoxide exposure. The employer called Poison Control, evacuated and ventilated the building, and took Employees #1 through #11 to the hospital, where they were admitted. Fire/rescue personnel arrived, but the affected employees were not on site. The forklift was found to have a faulty diaphragm and was repaired. The employer also installed ventilation and purchased a carbon monoxide monitor.