Abstract: On January 24, 2011, Employees #1, #2 and #3 were involved with activities to shut down a dairy for the day. Employees #1 and #2 were cleaning a cooler. A gas powered pressure washer was being used to clean the cooler. The cooler had no ventilation. After approximately 1 hr, Employee #1 left the cooler to summon for help and he became he very dizzy and was having difficulty breathing. Employee #1 was given oxygen at the scene and during transport by ambulance to a hospital, where he remained until the evening of the following day. Employee #2 was in and out of the cooler, and opened the doors at the end, was taken first to an emergency room, where his carboxyhemoglobin levels were 25, and then transported to another medical center, where he received treatment in the hyperbaric chamber. Employee #3 had been in the area and was transported to the hospital with Employee #2 and was discharged shortly thereafter.