Abstract: An outside contractor for bi-weekly cleaning of floors within the store was using a propane gas powered buffer to polish the tile floors. Store employees began experiencing symptoms of carbon monoxide poisoning 2 to 3 hours after initial exposure. Employees #1 through #12 were taken to the hospital and received medical treatment in a hyperbaric chamber. Carboxyhemoglobin levels were found in 3.7 to 26.8 percent range several hours after the employees had received 100 percent oxygen. This indicated that much higher levels would have been found if the employees had been immediately tested. The buffer's Honda engine, model GXV340, was found to be in need of a tune-up. All employees remained out of work the following day.