Abstract: At 7:45 a.m., Employee #1 was loading a truck when Employee #2 called to him that there was a large chlorine leak at the rail siding. Employee #1 activated the evacuation alarm, and called 911. Employees #1 and #2 donned SCBAs and went to site of the leak. The bleed-off valve was open, and was discharging large volumes of chlorine gas into the CPVC piping that led to a sodium hydroxide-filled scrubber. The CPVC piping had parted, and the chlorine was being discharged to the atmosphere. The bleed-off valve and the plant supply valve were closed, and Employees #1 and #2 then proceeded to the evacuation area. They had been exposed to chlorine gas while calling 911, prior to donning their SCBAs.