Abstract: On the morning of January 12, 2008, Employee #1 was found on the ground next to the tractor trailer Employee #1 had been driving by a manager. Employee #1 was dead. An autopsy determined the cause of death to be due to carbon monoxide (CO) toxicity. The Salt Lake City Technical Center conducted an investigation and determined that Employee #1 had been exposed to 330 parts per minutes (ppm) of CO, expressed as an 8-hour time-weighted average, which is more than six times the permissible exposure limit of CO. Direct reading air sampling was conducted and analyzed on the various CO sources such as the heaters, pressure washer, and hot water heater and excluded them as potential causes of the CO. The potential cause that was most likely to contributed to the incident was the operation of motor vehicles, indoors, without proper ventilation. A timeline based on interviews and the truck's GPS data indicated that the fatality was work related.