Abstract: On September 10, 2002, Employee #1, a receptionist, Employee #2, a salesman, and Employee #3, an industrial truck operator, were all working in an enclosed warehouse for varying lengths of time. Employee #3 was using a gas-powered forklift to re-arrange stock, and had been working approximately 3.5 hours with the doors to the building kept shut to keep out the heat. During this time, Employee #1 went in and out of the warehouse to do some filing. Employee #2 was in the building, preparing a sales package and attending a 1-hour meeting. After he finished using the fork truck, Employee #3 continued to work in the unventilated warehouse with the doors shut. All three workers suffered from the effects of exposure to carbon monoxide. Employee #2 had a carboxyhemoglobin level of 30.7 ppm. Employee #1 and Employee #3 had carboxyhemoglobin levels of approximately 13.6 ppm and 12.8 ppm, respectively. But, they received oxygen treatment and there was a much longer delay before their blood was drawn. Employee #2 was treated in a hyperbaric chamber and then released, but on condition he come in for follow-up visits for lingering symptoms. Calculated TWAs ranged from 86 ppm for Employee #1, 131 ppm for Employee #2, and 170 ppm for Employee #3, after accounting for the delay in measurement and other factors.