Abstract: On November 30, 1995, Employee #1 and six coworkers opened up their building in the morning. The contract cleaning service had used a propane-powered buffer the night before, and the workers began to experience symptoms of carbon monoxide poisoning. They were transported to a local hospital, where Employee #1 and three coworkers were treated in hyperbolic chambers; the other three coworkers were held for observation. All seven workers were expected to be released by the end of the day. The employer called the natural gas company to check for gas leaks. It continued monitoring the facility until the carbon monoxide readings were down to 10 ppm. The employer continued to ventilate the building for an additional two hours, and then opened for business.