Abstract: Employee #1 was overcome by carbon monoxide when he attempted to use a LP floor burnisher in a supermarket. He was assigned to clean the supermarket during store closing hours. The job takes about 4.5 hours to complete. The operation of LP floor burnisher takes about 1.5-2 hours and is the last operation to be done. Employee #1 was using a recently purchased used machine that he had never operated before. He had about one hour of burnishing to do when he stopped to let early arriving employees into the store. He normally shuts off the machine by closing the valve at the cylinder in order to bleed the fuel lines. This time, the machine failed to stop after several seconds and continued to run for several minutes. He returned after a smoke break to restart the machine, and it produced a loud bang when he started it. He observed that the machine was not running well and bent over to investigate. He passed out. As he was falling, he grabbed the handle and pulled it over on himself with it still running. Other employees in the store heard the backfire and saw smoke rising. Upon investigation, they discovered Employee #1 on his back going into convulsions with the machine still running and spilling out oil and producing copious amounts of smoke that quickly began to fill the store. His coworkers could not shut off machine either with the throttle control or by closing the cylinder valve. Medical personnel arrived within two to three minutes and administered oxygen and transported Employee #1 to the hospital emergency room located next door. The medical staff drew a blood sample for blood gasses and Employee #1 had a COHb of 12.3. The hospital wanted to hold him for observation, but he refused and was released after treatment. Employee #1 tested negative for alcohol or drugs and was not on any medication.