Abstract: An unplanned rupture occurred in a pressurized bleed-down pipeline that was carrying approximately 130 psi of liquid chlorine in the A-B chemical prep area. All remaining liquid chlorine was to be purged from system line 4 through the bleed down line into a bleed down tank containing caustic substances. This was being done so that a valve at the head of the line could be replaced in order to repair a leak. A chemical unloader operator opened the valve, resulting in a gas cloud from a leak of 6.8 pounds of liquid chlorine. Employees #1 through #6 were all in the general vicinity of the leak. They were either passing through the area or working downwind from it when they inhaled the chlorine. The chemical unloader operator was not affected. Employee #1, a chemical operator, was the only person affected who had been aware of the purging process that was taking place in order to repair the leaking valve.