Abstract: At approximately 9:00 a.m. on October 10, 1991, Employee #1 began sawing a 10 ft strip across the concrete floor of a 40 ft by 30 ft by 12 ft building. Within a few minutes, he thought he needed fresh air and left the building to allow polluted air to clear out. Employee #1 used a gasoline engine powered concrete saw to cut approximately 5 ft of the assigned 10 ft strip. After a few minutes of resting, he returned to finish the job. Employee #1 was able to finish the job, but felt dizzy and nauseated and again went outside to get fresh air. Somebody observed that Employee #1 appeared pale and called the local paramedics (the fire department). Employee #1 was taken to Mercy Medical Center, where a blood test was performed. The carbon monoxide levels in his blood were found to be slightly elevated. Within a few hours, Employee #1 had fully recovered.