Abstract: At approximately 9:50 a.m. on December 2, 1998, Employee #1 was replacing an empty chlorine gas bottle with a new one in the pool house of a high school. During the process of disconnecting the empty cylinder from the system, chlorine gas leak from the system. Employee #1 ran out of the room and asked help from Employee #2 who happened to be in the area at that time. Employee #2 told Employee #1 to leave the area since Employee #1 appeared to have trouble breathing. Employee #2 put on a mask, entered the room and tried to shut off the bottle to stop the leak. As Employee #2 entered the room he could hear the hissing sound of the gas. Employee #2 determined the bottle was shut off, but the gas was still leaking. Both employees were taken to the hospital. Employee #1 suffered from acute exposure to chlorine gas having shortness of breath, was given oxygen treatment and released the next day. Employee #2 also suffered some irritation and was released the same day.