Abstract: At approximately 6:15 p.m. on February 22, 1996, Employees #1, #2, #3, and #4 were troweling concrete in a newly constructed building. Employees #1 and #2 periodically operated a gasoline-powered Razorback trowel while Employees #3 and #4 hand troweled the outer edges of the surface. The area of the building was approximately 80 ft by 100 ft. Most of the doors in the building were kept closed to keep heat in the building and to allow the concrete to cure; however, some ventilation for the work area was supplied by two stand up fans and through one open personnel door across from a garage door that was opened 1/4 of the way. By the end of the day, carbon monoxide levels were high and the employees became dizzy, sleepy, and nauseous and began to suffer headaches. Employees #1 through #4 were hospitalized for carbon monoxide poisoning.