Abstract: A four-member cleanup crew that was working the midnight shift to complete a biannual operation used a gas-fueled pressure washer indoors without benefit of engineering or administrative controls, or personal protective equipment. The washer ran indoors for approximately four hours. Interviews with employees indicate that the washer may not have been well maintained (emitting smoky exhaust, noisy, stalling), and that two on-duty supervisors did not respond to this information; nor to the employees' reporting symptoms that included nausea, lightheadedness, dizziness; nor to an employee lying on the floor in the work area. Employees #1 through #8, four members of the cleanup crew and members of the midnight freight crew, inhaled carbon monoxide. They were hospitalized. A blood sample on Employee #1 showed a carboxyhemoglobin level of 23.8 percent.