Abstract: At 6:30 p.m. on August 15, 2005, Employees #1, #2, #3, and #4 were working at the Lawry's The Prime Rib, Inc., restaurant. At 6:30, Employee #1 was washing dishes, when he felt lightheaded. He stumbled and fell down three stairs, injuring his leg. Approximately thirty minutes later, two more dishwashers felt lightheaded and started stumbling. The dish area is adjacent to the main dining room, and a dining room server fell ill too. Emergency medical services were called, and the four employees were taken to the hospital for carbon monoxide exposure. Two of the employees (both dishwashers) were admitted; the other two (one of the dishwashers and the server) were not. After the fire department measured carbon monoxide in the air, the facility was evacuated. The local gas utility company was onsite as well; it measured a carbon monoxide level of approximately 1,028 parts per million (ppm). The dishwashing machine is composed of three gas-powered units: a glass washer, a dish washer, and a hot water booster heater. The gas-powered hot water booster heater unit exhaust duct was leaking. The booster heater was identified as the source of the carbon monoxide. A carbon monoxide detector was located in an adjacent kitchen area.