Abstract: At 5:30 a.m. on January 25, 2010, Employee #1 and a coworker were investigating a 62-in. long by 48-in. wide by 61- in. deep vault for a possible steam leak, on the hospital premises in the medical center after an all night rain storm. Employee #1 stated that the steam was rising from the vault in a soft plume. The examination of the vault piping and the floor with a flash light did not reveal any steam leaks, the steam plume source, water in the bottom of the vault, or indication of any hazards in the vault. Employee #1 then lowered himself into the vault and stepped on to a steam valve. As he did so, he slipped off the valve approximately 18 in. into undetected rain water intrusion, covering the vault floor that was heated up to 212 degrees by the 338-degree steam lines. Employee #1 was immediately rescued by the coworker however he sustained second and third degree burns to his right and left legs below the knees. Employee #1 was hospitalized.