Abstract: Employee #1, a mechanic, entered a trailer-mounted deaerator tank, which was a confined space, to clean the walls and to remove a pipe elbow. The worker used an oxygen-acetylene torch to heat and then cut the pipe elbow. The heating and cutting process transformed the water in the pipe to steam. Employee #1 exited the 60 in. diameter by 20 foot long cylindrical tank several times, completed his work and left for the day. On the way home, Employee #1 began feeling ill and went to the hospital later that evening. He was hospitalized for observation and treatment of acute pulmonary edema, most likely caused by inhalation of aerosols, bio-aerosols or chemical contaminants, contained in the steam that formed inside the tank. The company did not have procedures for permit-required confined space entry or for the use of ventilation and personal protective equipment.