Abstract: On June 29, 2005, Employee #1 was involved in the following the maintenance activities in the Chloropyridines Complex at the employer's chemical manufacturing facility. Employee #1 was returning a reactor vessel to service. He was attempting to do a pressure and leak pipeline test using chlorine gas. The pipeline was supposed to be pressure tested with nitrogen gas during the previous shift. During the test Employee #1 noticed that a valve leading from the reactor vessel was closed. When Employee #1 opened the valve, chlorine gas began to escape from a loose downstream flange. About 180 pounds of chlorine was released. Employee #1 returned to close the valve without donning respiratory protection and inhaled chlorine gas. Employee #1 was hospitalized for more than 24 hours for acute chemical exposure. Employee #2, a contractor employee, was escaping from the released chlorine gas and suffered an asthma attack. Employee #2 was treated and released the same day.